diff --git a/configs/tsconfig.json b/configs/tsconfig.json
index 7842299..401b459 100644
--- a/configs/tsconfig.json
+++ b/configs/tsconfig.json
@@ -1,14 +1,15 @@
 {
     "compilerOptions": {
         "target": "ES2022",
-        "module": "ES2022",
+        "module": "node16",
         "strict": true,
         "noUnusedParameters": true,
         "noImplicitReturns": true,
         "noUnusedLocals": true,
         "removeComments": false,
         "preserveConstEnums": true,
-        "moduleResolution": "Bundler",
+        "moduleResolution": "node16",
+        "verbatimModuleSyntax": true,
         "newLine": "LF",
         "sourceMap": true,
         "declaration": true,
diff --git a/packages/aes-kw/aes-kw.test.ts b/packages/aes-kw/aes-kw.test.ts
index 172620f..b25f4ce 100644
--- a/packages/aes-kw/aes-kw.test.ts
+++ b/packages/aes-kw/aes-kw.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { AESKW } from "./aes-kw";
+import { AESKW } from "./aes-kw.js";
 import { encode, decode } from "@stablelib/hex";
 
 // Test vectors sourced from RFC 3394
diff --git a/packages/aes/aes.bench.ts b/packages/aes/aes.bench.ts
index d22304b..64f1c41 100644
--- a/packages/aes/aes.bench.ts
+++ b/packages/aes/aes.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { AES } from "./aes";
+import { AES } from "./aes.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const key = byteSeq(32);
diff --git a/packages/aes/aes.test.ts b/packages/aes/aes.test.ts
index fde4bcc..964ea51 100644
--- a/packages/aes/aes.test.ts
+++ b/packages/aes/aes.test.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 import { describe, expect, it } from 'vitest';
-import { AES } from "./aes";
+import { AES } from "./aes.js";
 import { encode, decode } from "@stablelib/hex";
 
 // TODO(dchest): add more AES test vectors.
diff --git a/packages/base64/base64.bench.ts b/packages/base64/base64.bench.ts
index 076f9a6..c824dfd 100644
--- a/packages/base64/base64.bench.ts
+++ b/packages/base64/base64.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { encode, decode } from "./base64";
+import { encode, decode } from "./base64.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 let buf = byteSeq(1024);
diff --git a/packages/base64/base64.test.ts b/packages/base64/base64.test.ts
index c575926..8098fa7 100644
--- a/packages/base64/base64.test.ts
+++ b/packages/base64/base64.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { encode, decode, encodeURLSafe, decodeURLSafe } from "./base64";
+import { encode, decode, encodeURLSafe, decodeURLSafe } from "./base64.js";
 
 const testVectors: [number[], string][] = [
     // https://tools.ietf.org/html/rfc4648
diff --git a/packages/binary/binary.test.ts b/packages/binary/binary.test.ts
index b88278f..9e72a2b 100644
--- a/packages/binary/binary.test.ts
+++ b/packages/binary/binary.test.ts
@@ -11,7 +11,7 @@ import {
     readUintLE, writeUintLE, readUintBE, writeUintBE,
     readFloat32BE, writeFloat32BE, readFloat64BE, writeFloat64BE,
     readFloat32LE, writeFloat32LE, readFloat64LE, writeFloat64LE
-} from "./binary";
+} from "./binary.js";
 
 const int16BEVectors: [number, number[]][] = [
     [0, [0, 0]],
diff --git a/packages/blake2b/blake2b.bench.ts b/packages/blake2b/blake2b.bench.ts
index 4df3872..0a922e1 100644
--- a/packages/blake2b/blake2b.bench.ts
+++ b/packages/blake2b/blake2b.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { hash } from "./blake2b";
+import { hash } from "./blake2b.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 let buf1M = byteSeq(1024 << 10);
diff --git a/packages/blake2b/blake2b.test.ts b/packages/blake2b/blake2b.test.ts
index a3547b4..3c867f1 100644
--- a/packages/blake2b/blake2b.test.ts
+++ b/packages/blake2b/blake2b.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { BLAKE2b } from "./blake2b";
+import { BLAKE2b } from "./blake2b.js";
 import { encode } from "@stablelib/hex";
 
 const vectors = [
diff --git a/packages/blake2s/blake2s.bench.ts b/packages/blake2s/blake2s.bench.ts
index 612a739..2626d1b 100644
--- a/packages/blake2s/blake2s.bench.ts
+++ b/packages/blake2s/blake2s.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { hash } from "./blake2s";
+import { hash } from "./blake2s.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 let buf1M = byteSeq(1024 << 10);
diff --git a/packages/blake2s/blake2s.test.ts b/packages/blake2s/blake2s.test.ts
index d070109..54ae618 100644
--- a/packages/blake2s/blake2s.test.ts
+++ b/packages/blake2s/blake2s.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { BLAKE2s } from "./blake2s";
+import { BLAKE2s } from "./blake2s.js";
 import { encode } from "@stablelib/hex";
 
 const vectors = [
diff --git a/packages/blake2xs/blake2xs.bench.ts b/packages/blake2xs/blake2xs.bench.ts
index 9e887e8..e0afcba 100644
--- a/packages/blake2xs/blake2xs.bench.ts
+++ b/packages/blake2xs/blake2xs.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { xof } from "./blake2xs";
+import { xof } from "./blake2xs.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 let key = byteSeq(32);
diff --git a/packages/blake2xs/blake2xs.test.ts b/packages/blake2xs/blake2xs.test.ts
index 11114bd..9be457d 100644
--- a/packages/blake2xs/blake2xs.test.ts
+++ b/packages/blake2xs/blake2xs.test.ts
@@ -4,7 +4,7 @@
 import { describe, expect, it } from 'vitest';
 import * as hex from "@stablelib/hex";
 import { concat } from "@stablelib/bytes";
-import { BLAKE2Xs } from "./blake2xs";
+import { BLAKE2Xs } from "./blake2xs.js";
 
 /* eslint:disable */
 const vectors = [
diff --git a/packages/bytereader/bytereader.bench.ts b/packages/bytereader/bytereader.bench.ts
index bb0128c..10073dc 100644
--- a/packages/bytereader/bytereader.bench.ts
+++ b/packages/bytereader/bytereader.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { ByteReader } from "./bytereader";
+import { ByteReader } from "./bytereader.js";
 import { report, benchmark, byteSeq } from "@stablelib/benchmark";
 
 const buf = byteSeq(8 << 10);
diff --git a/packages/bytereader/bytereader.test.ts b/packages/bytereader/bytereader.test.ts
index 7c1ebcc..c3c3ee9 100644
--- a/packages/bytereader/bytereader.test.ts
+++ b/packages/bytereader/bytereader.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { ByteReader } from "./bytereader";
+import { ByteReader } from "./bytereader.js";
 
 describe("ByteReader", () => {
     it("should read bytes", () => {
diff --git a/packages/bytes/bytes.bench.ts b/packages/bytes/bytes.bench.ts
index 4e20af8..7bf1616 100644
--- a/packages/bytes/bytes.bench.ts
+++ b/packages/bytes/bytes.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { concat } from "./bytes";
+import { concat } from "./bytes.js";
 import { benchmark, report } from "@stablelib/benchmark";
 
 const a0 = new Uint8Array([1, 2, 3]);
diff --git a/packages/bytes/bytes.test.ts b/packages/bytes/bytes.test.ts
index 7b7096e..1cb038c 100644
--- a/packages/bytes/bytes.test.ts
+++ b/packages/bytes/bytes.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { concat } from "./bytes";
+import { concat } from "./bytes.js";
 
 describe("concat", () => {
     it("should concatenate byte arrays", () => {
diff --git a/packages/bytewriter/bytewriter.bench.ts b/packages/bytewriter/bytewriter.bench.ts
index 2218f6f..f89d7a6 100644
--- a/packages/bytewriter/bytewriter.bench.ts
+++ b/packages/bytewriter/bytewriter.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { ByteWriter } from "./bytewriter";
+import { ByteWriter } from "./bytewriter.js";
 import { report, benchmark, byteSeq } from "@stablelib/benchmark";
 
 report("ByteWriter write", benchmark(() => benchmarkWrite(8192), 8192));
diff --git a/packages/bytewriter/bytewriter.test.ts b/packages/bytewriter/bytewriter.test.ts
index 58cf807..c2e726b 100644
--- a/packages/bytewriter/bytewriter.test.ts
+++ b/packages/bytewriter/bytewriter.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { ByteWriter } from "./bytewriter";
+import { ByteWriter } from "./bytewriter.js";
 
 describe("ByteWriter", () => {
     it("should write bytes", () => {
diff --git a/packages/cbor/cbor.bench.ts b/packages/cbor/cbor.bench.ts
index c651e58..c2cdf4a 100644
--- a/packages/cbor/cbor.bench.ts
+++ b/packages/cbor/cbor.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { encode, decode, Tagged } from "./cbor";
+import { encode, decode, Tagged } from "./cbor.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf = byteSeq(128);
diff --git a/packages/cbor/cbor.test.ts b/packages/cbor/cbor.test.ts
index 52751e2..f8d9afe 100644
--- a/packages/cbor/cbor.test.ts
+++ b/packages/cbor/cbor.test.ts
@@ -4,11 +4,11 @@
 import { describe, expect, it } from 'vitest';
 import * as hex from "@stablelib/hex";
 import { concat } from "@stablelib/bytes";
-import type { TaggedEncoder, TaggedDecoder} from "./cbor";
+import type { TaggedEncoder, TaggedDecoder} from "./cbor.js";
 import {
     encode, decode, Simple, Tagged,
     DEFAULT_TAGGED_ENCODERS, DEFAULT_TAGGED_DECODERS
-} from "./cbor";
+} from "./cbor.js";
 
 // Test vectors from RFC 7049: Appendix A.  Examples.
 const encoderTestVectors = [
diff --git a/packages/chacha-drbg/chacha-drbg.bench.ts b/packages/chacha-drbg/chacha-drbg.bench.ts
index c6fe8e4..ed9577b 100644
--- a/packages/chacha-drbg/chacha-drbg.bench.ts
+++ b/packages/chacha-drbg/chacha-drbg.bench.ts
@@ -1,8 +1,8 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { ChaChaDRBG } from "./chacha-drbg";
-import type { RandomSource } from "@stablelib/random/source";
+import { ChaChaDRBG } from "./chacha-drbg.js";
+import type { RandomSource } from "@stablelib/random/source/index.js";
 import { benchmark, report } from "@stablelib/benchmark";
 
 class XKCDSource implements RandomSource {
diff --git a/packages/chacha/chacha.bench.ts b/packages/chacha/chacha.bench.ts
index 3b51cd3..a233bb8 100644
--- a/packages/chacha/chacha.bench.ts
+++ b/packages/chacha/chacha.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { streamXOR } from "./chacha";
+import { streamXOR } from "./chacha.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf16K = byteSeq(16 << 10);
diff --git a/packages/chacha/chacha.test.ts b/packages/chacha/chacha.test.ts
index 0c34d97..2284ade 100644
--- a/packages/chacha/chacha.test.ts
+++ b/packages/chacha/chacha.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { streamXOR, stream } from "./chacha";
+import { streamXOR, stream } from "./chacha.js";
 import { encode, decode } from "@stablelib/hex";
 
 function seq(len: number): Uint8Array {
diff --git a/packages/chacha20poly1305/chacha20poly1305.bench.ts b/packages/chacha20poly1305/chacha20poly1305.bench.ts
index a638db0..95aeaee 100644
--- a/packages/chacha20poly1305/chacha20poly1305.bench.ts
+++ b/packages/chacha20poly1305/chacha20poly1305.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { ChaCha20Poly1305 } from "./chacha20poly1305";
+import { ChaCha20Poly1305 } from "./chacha20poly1305.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf8192 = byteSeq(8192);
diff --git a/packages/chacha20poly1305/chacha20poly1305.test.ts b/packages/chacha20poly1305/chacha20poly1305.test.ts
index 819b346..4c4432f 100644
--- a/packages/chacha20poly1305/chacha20poly1305.test.ts
+++ b/packages/chacha20poly1305/chacha20poly1305.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { ChaCha20Poly1305 } from "./chacha20poly1305";
+import { ChaCha20Poly1305 } from "./chacha20poly1305.js";
 import { encode, decode } from "@stablelib/hex";
 
 const testVectors = [
diff --git a/packages/cmac/cmac.bench.ts b/packages/cmac/cmac.bench.ts
index fc67d37..de85489 100644
--- a/packages/cmac/cmac.bench.ts
+++ b/packages/cmac/cmac.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { CMAC } from "./cmac";
+import { CMAC } from "./cmac.js";
 import { AES } from "@stablelib/aes";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
diff --git a/packages/cmac/cmac.test.ts b/packages/cmac/cmac.test.ts
index 1939ee3..2aa53ae 100644
--- a/packages/cmac/cmac.test.ts
+++ b/packages/cmac/cmac.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { CMAC } from "./cmac";
+import { CMAC } from "./cmac.js";
 import { AES } from "@stablelib/aes";
 import { encode, decode } from "@stablelib/hex";
 
diff --git a/packages/constant-time/constant-time.test.ts b/packages/constant-time/constant-time.test.ts
index faac42b..ca210af 100644
--- a/packages/constant-time/constant-time.test.ts
+++ b/packages/constant-time/constant-time.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { select, lessOrEqual, compare, equal } from "./constant-time";
+import { select, lessOrEqual, compare, equal } from "./constant-time.js";
 
 describe("constant-time.select", () => {
     it("should select correct value", () => {
diff --git a/packages/ctr/ctr.bench.ts b/packages/ctr/ctr.bench.ts
index 6fda54d..88f4632 100644
--- a/packages/ctr/ctr.bench.ts
+++ b/packages/ctr/ctr.bench.ts
@@ -3,7 +3,7 @@
 
 import { AES } from "@stablelib/aes";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
-import { CTR } from "./ctr";
+import { CTR } from "./ctr.js";
 
 const buf8192 = byteSeq(8192);
 const buf1111 = byteSeq(1111);
diff --git a/packages/ctr/ctr.test.ts b/packages/ctr/ctr.test.ts
index 9f48197..673b0b6 100644
--- a/packages/ctr/ctr.test.ts
+++ b/packages/ctr/ctr.test.ts
@@ -4,7 +4,7 @@
 import { describe, expect, it } from 'vitest';
 import { AES } from "@stablelib/aes";
 import { encode, decode } from "@stablelib/hex";
-import { CTR } from "./ctr";
+import { CTR } from "./ctr.js";
 
 describe("AES-CTR", () => {
     const v = {
diff --git a/packages/ed25519/ed25519.bench.ts b/packages/ed25519/ed25519.bench.ts
index e556ecd..739ee72 100644
--- a/packages/ed25519/ed25519.bench.ts
+++ b/packages/ed25519/ed25519.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { sign, verify, generateKeyPairFromSeed, generateKeyPair } from "./ed25519";
+import { sign, verify, generateKeyPairFromSeed, generateKeyPair } from "./ed25519.js";
 import { benchmark, report } from "@stablelib/benchmark";
 
 const k = generateKeyPair();
diff --git a/packages/ed25519/ed25519.test.ts b/packages/ed25519/ed25519.test.ts
index 2c241e6..f5184eb 100644
--- a/packages/ed25519/ed25519.test.ts
+++ b/packages/ed25519/ed25519.test.ts
@@ -3,7 +3,7 @@
 
 import { describe, expect, it } from 'vitest';
 import { encode, decode } from "@stablelib/base64";
-import { sign, verify, generateKeyPair, extractPublicKeyFromSecretKey, convertPublicKeyToX25519, convertSecretKeyToX25519 } from "./ed25519";
+import { sign, verify, generateKeyPair, extractPublicKeyFromSecretKey, convertPublicKeyToX25519, convertSecretKeyToX25519 } from "./ed25519.js";
 
 /* eslint:disable */
 const testVectors = [
diff --git a/packages/float/float.test.ts b/packages/float/float.test.ts
index a6193ea..6484243 100644
--- a/packages/float/float.test.ts
+++ b/packages/float/float.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { isNegativeZero, fround } from "./float";
+import { isNegativeZero, fround } from "./float.js";
 
 describe("isNegativeZero", () => {
     it("should return true for -0", () => {
diff --git a/packages/gcm/gcm.bench.ts b/packages/gcm/gcm.bench.ts
index 9c3d977..7135c16 100644
--- a/packages/gcm/gcm.bench.ts
+++ b/packages/gcm/gcm.bench.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { AES } from "@stablelib/aes";
-import { GCM } from "./gcm";
+import { GCM } from "./gcm.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf8192 = byteSeq(8192);
diff --git a/packages/gcm/gcm.test.ts b/packages/gcm/gcm.test.ts
index 64cb85a..7439589 100644
--- a/packages/gcm/gcm.test.ts
+++ b/packages/gcm/gcm.test.ts
@@ -3,7 +3,7 @@
 
 import { describe, expect, it } from 'vitest';
 import { AES } from "@stablelib/aes";
-import { GCM } from "./gcm";
+import { GCM } from "./gcm.js";
 import { encode, decode } from "@stablelib/hex";
 
 // TODO(dchest): add more test vectors.
diff --git a/packages/gf256/gf256.bench.ts b/packages/gf256/gf256.bench.ts
index 9dbfab4..f89d4bc 100644
--- a/packages/gf256/gf256.bench.ts
+++ b/packages/gf256/gf256.bench.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { benchmark, report } from "@stablelib/benchmark";
-import { mul, div } from "./gf256";
+import { mul, div } from "./gf256.js";
 
 report("gf256.mul", benchmark(() => mul(100, 18)));
 report("gf256.div", benchmark(() => div(100, 18)));
diff --git a/packages/gf256/gf256.test.ts b/packages/gf256/gf256.test.ts
index aca1293..0b568e4 100644
--- a/packages/gf256/gf256.test.ts
+++ b/packages/gf256/gf256.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { add, sub, mul, div } from "./gf256";
+import { add, sub, mul, div } from "./gf256.js";
 
 
 describe("add/sub", () => {
diff --git a/packages/halfsiphash/halfsiphash.bench.ts b/packages/halfsiphash/halfsiphash.bench.ts
index 47b92bf..ae9f121 100644
--- a/packages/halfsiphash/halfsiphash.bench.ts
+++ b/packages/halfsiphash/halfsiphash.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2017 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { halfSipHash } from "./halfsiphash";
+import { halfSipHash } from "./halfsiphash.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf1M = byteSeq(1024 << 10);
diff --git a/packages/halfsiphash/halfsiphash.test.ts b/packages/halfsiphash/halfsiphash.test.ts
index a41101e..fa713e2 100644
--- a/packages/halfsiphash/halfsiphash.test.ts
+++ b/packages/halfsiphash/halfsiphash.test.ts
@@ -3,7 +3,7 @@
 
 import { describe, expect, it } from 'vitest';
 import * as hex from "@stablelib/hex";
-import { halfSipHash } from "./halfsiphash";
+import { halfSipHash } from "./halfsiphash.js";
 
 const testVectors = [
     "A9359F5B",
diff --git a/packages/hex/hex.bench.ts b/packages/hex/hex.bench.ts
index e5c8547..c763fa6 100644
--- a/packages/hex/hex.bench.ts
+++ b/packages/hex/hex.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { encode, decode } from "./hex";
+import { encode, decode } from "./hex.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 let buf = byteSeq(1024);
diff --git a/packages/hex/hex.test.ts b/packages/hex/hex.test.ts
index 1243ae2..8d5a646 100644
--- a/packages/hex/hex.test.ts
+++ b/packages/hex/hex.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { encode, decode } from "./hex";
+import { encode, decode } from "./hex.js";
 
 let buf = new Uint8Array(256);
 for (let i = 0; i < buf.length; i++) {
diff --git a/packages/hkdf/hkdf.bench.ts b/packages/hkdf/hkdf.bench.ts
index 692a404..732f9c1 100644
--- a/packages/hkdf/hkdf.bench.ts
+++ b/packages/hkdf/hkdf.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { HKDF } from "./hkdf";
+import { HKDF } from "./hkdf.js";
 import { SHA256 } from "@stablelib/sha256";
 import { SHA512 } from "@stablelib/sha512";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
diff --git a/packages/hkdf/hkdf.test.ts b/packages/hkdf/hkdf.test.ts
index 3d96454..e9a6b70 100644
--- a/packages/hkdf/hkdf.test.ts
+++ b/packages/hkdf/hkdf.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { HKDF } from "./hkdf";
+import { HKDF } from "./hkdf.js";
 import { SHA256, DIGEST_LENGTH } from "@stablelib/sha256";
 import { encode, decode } from "@stablelib/hex";
 
diff --git a/packages/hmac-drbg/hmac-drbg.bench.ts b/packages/hmac-drbg/hmac-drbg.bench.ts
index b0676c3..87ed461 100644
--- a/packages/hmac-drbg/hmac-drbg.bench.ts
+++ b/packages/hmac-drbg/hmac-drbg.bench.ts
@@ -1,8 +1,8 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { HMACDRBG } from "./hmac-drbg";
-import type { RandomSource } from "@stablelib/random/source";
+import { HMACDRBG } from "./hmac-drbg.js";
+import type { RandomSource } from "@stablelib/random/source/index.js";
 import { benchmark, report } from "@stablelib/benchmark";
 
 class XKCDSource implements RandomSource {
diff --git a/packages/hmac/hmac.test.ts b/packages/hmac/hmac.test.ts
index 8043aef..a71dc2e 100644
--- a/packages/hmac/hmac.test.ts
+++ b/packages/hmac/hmac.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { HMAC, hmac } from "./hmac";
+import { HMAC, hmac } from "./hmac.js";
 import { SHA256 } from "@stablelib/sha256";
 import { SHA224 } from "@stablelib/sha224";
 import { encode } from "@stablelib/base64";
diff --git a/packages/int/int.test.ts b/packages/int/int.test.ts
index 3a7a353..70258f7 100644
--- a/packages/int/int.test.ts
+++ b/packages/int/int.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { mul, add, sub } from "./int";
+import { mul, add, sub } from "./int.js";
 
 describe("int.mul", () => {
     it("should overflow", () => {
diff --git a/packages/keyagreement/concat.ts b/packages/keyagreement/concat.ts
index d08bcd4..9e728c5 100644
--- a/packages/keyagreement/concat.ts
+++ b/packages/keyagreement/concat.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import type { KeyAgreement } from "./keyagreement";
+import type { KeyAgreement } from "./keyagreement.js";
 import { concat } from "@stablelib/bytes";
 
 /**
diff --git a/packages/nacl/box.ts b/packages/nacl/box.ts
index 9a3d487..2f60ffc 100644
--- a/packages/nacl/box.ts
+++ b/packages/nacl/box.ts
@@ -3,7 +3,7 @@
 
 import { scalarMult } from "@stablelib/x25519";
 import { hsalsa } from "@stablelib/xsalsa20";
-import { secretBox, openSecretBox } from "./secretbox";
+import { secretBox, openSecretBox } from "./secretbox.js";
 import { wipe } from "@stablelib/wipe";
 
 export { generateKeyPair } from "@stablelib/x25519";
diff --git a/packages/nacl/nacl.ts b/packages/nacl/nacl.ts
index b83d847..c7ea42f 100644
--- a/packages/nacl/nacl.ts
+++ b/packages/nacl/nacl.ts
@@ -5,5 +5,5 @@
  * Package nacl implements NaCl (Networking and Cryptography library) cryptography.
  */
 
-export * from "./box";
-export * from "./secretbox";
+export * from "./box.js";
+export * from "./secretbox.js";
diff --git a/packages/nacl/secretbox.bench.ts b/packages/nacl/secretbox.bench.ts
index f51c74e..08e0e80 100644
--- a/packages/nacl/secretbox.bench.ts
+++ b/packages/nacl/secretbox.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { secretBox } from "./secretbox";
+import { secretBox } from "./secretbox.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf8192 = byteSeq(8192);
diff --git a/packages/nacl/secretbox.test.ts b/packages/nacl/secretbox.test.ts
index 5e17574..ff8d671 100644
--- a/packages/nacl/secretbox.test.ts
+++ b/packages/nacl/secretbox.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { secretBox, openSecretBox } from "./secretbox";
+import { secretBox, openSecretBox } from "./secretbox.js";
 import { encode, decode } from "@stablelib/hex";
 
 describe("secretBox", () => {
diff --git a/packages/newhope/newhope.bench.ts b/packages/newhope/newhope.bench.ts
index e5c7774..403a70a 100644
--- a/packages/newhope/newhope.bench.ts
+++ b/packages/newhope/newhope.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { NewHope } from "./newhope";
+import { NewHope } from "./newhope.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const seed = byteSeq(32);
diff --git a/packages/newhope/newhope.test.ts b/packages/newhope/newhope.test.ts
index c59a44e..02543fb 100644
--- a/packages/newhope/newhope.test.ts
+++ b/packages/newhope/newhope.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { NewHope } from "./newhope";
+import { NewHope } from "./newhope.js";
 import { stream } from "@stablelib/chacha";
 import * as hex from "@stablelib/hex";
 
diff --git a/packages/newhope/newhope.ts b/packages/newhope/newhope.ts
index 2b7a803..1c7d5be 100644
--- a/packages/newhope/newhope.ts
+++ b/packages/newhope/newhope.ts
@@ -28,8 +28,8 @@
 
 import type { RandomSource } from "@stablelib/random";
 import { SHAKE128, SHA3256 } from "@stablelib/sha3";
-import type { SeedExpander} from "./custom";
-import { CustomNewHope } from "./custom";
+import type { SeedExpander } from "./custom.js";
+import { CustomNewHope } from "./custom.js";
 
 export {
     PUBLIC_SEED_LENGTH,
@@ -37,7 +37,7 @@ export {
     OFFER_MESSAGE_LENGTH,
     ACCEPT_MESSAGE_LENGTH,
     SAVED_STATE_LENGTH
-} from "./custom";
+} from "./custom.js";
 
 // Byte length of shared key.
 export const SHARED_KEY_LENGTH = 32; // SHA-3 digest length
diff --git a/packages/pbkdf2/pbkdf2.bench.ts b/packages/pbkdf2/pbkdf2.bench.ts
index 8cbfe41..137fbbb 100644
--- a/packages/pbkdf2/pbkdf2.bench.ts
+++ b/packages/pbkdf2/pbkdf2.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { deriveKey } from "./pbkdf2";
+import { deriveKey } from "./pbkdf2.js";
 import { SHA256 } from "@stablelib/sha256";
 import { SHA512 } from "@stablelib/sha512";
 import { SHA3512 } from "@stablelib/sha3";
diff --git a/packages/pbkdf2/pbkdf2.test.ts b/packages/pbkdf2/pbkdf2.test.ts
index 9578b3d..9260daf 100644
--- a/packages/pbkdf2/pbkdf2.test.ts
+++ b/packages/pbkdf2/pbkdf2.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { deriveKey } from "./pbkdf2";
+import { deriveKey } from "./pbkdf2.js";
 import { SHA256 } from "@stablelib/sha256";
 import { SHA224 } from "@stablelib/sha224";
 import { SHA512 } from "@stablelib/sha512";
diff --git a/packages/poly1305/poly1305.bench.ts b/packages/poly1305/poly1305.bench.ts
index 4d1599e..40d807c 100644
--- a/packages/poly1305/poly1305.bench.ts
+++ b/packages/poly1305/poly1305.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { oneTimeAuth } from "./poly1305";
+import { oneTimeAuth } from "./poly1305.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf8192 = byteSeq(8192);
diff --git a/packages/poly1305/poly1305.test.ts b/packages/poly1305/poly1305.test.ts
index be7299b..884a34a 100644
--- a/packages/poly1305/poly1305.test.ts
+++ b/packages/poly1305/poly1305.test.ts
@@ -4,7 +4,7 @@
 import { describe, expect, it } from 'vitest';
 import { encode, decode } from "@stablelib/hex";
 import { concat } from "@stablelib/bytes";
-import { oneTimeAuth, Poly1305 } from "./poly1305";
+import { oneTimeAuth, Poly1305 } from "./poly1305.js";
 
 const testVectors = [
         {
diff --git a/packages/random/random.test.ts b/packages/random/random.test.ts
index 5853ff1..1cfda61 100644
--- a/packages/random/random.test.ts
+++ b/packages/random/random.test.ts
@@ -4,7 +4,7 @@
 import { describe, expect, it } from 'vitest';
 import {
     randomBytes, randomUint32, randomString, randomStringForEntropy
-} from "./random";
+} from "./random.js";
 
 describe("randomBytes", () => {
     it("should generate random bytes", () => {
diff --git a/packages/random/random.ts b/packages/random/random.ts
index b358ea1..360c2f0 100644
--- a/packages/random/random.ts
+++ b/packages/random/random.ts
@@ -6,12 +6,12 @@
  * cryptographically secure random byte generator.
  */
 
-import type { RandomSource } from "./source";
-import { SystemRandomSource } from "./source/system";
+import type { RandomSource } from "./source/index.js";
+import { SystemRandomSource } from "./source/system.js";
 import { readUint32LE } from "@stablelib/binary";
 import { wipe } from "@stablelib/wipe";
 
-export { RandomSource } from "./source";
+export type { RandomSource } from "./source/index.js";
 
 export const defaultRandomSource = new SystemRandomSource();
 
diff --git a/packages/random/source/system.test.ts b/packages/random/source/system.test.ts
index 2ec421c..846ff99 100644
--- a/packages/random/source/system.test.ts
+++ b/packages/random/source/system.test.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 import { describe, expect, it } from 'vitest';
-import { SystemRandomSource } from "./system";
+import { SystemRandomSource } from "./system.js";
 
 describe("SystemRandomSource.randomBytes", () => {
 
diff --git a/packages/random/source/system.ts b/packages/random/source/system.ts
index ddd000f..727af0c 100644
--- a/packages/random/source/system.ts
+++ b/packages/random/source/system.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2024 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { RandomSource } from "./";
+import type { RandomSource } from "./index.js";
 
 const QUOTA = 65536;
 
diff --git a/packages/salsa20/salsa20.bench.ts b/packages/salsa20/salsa20.bench.ts
index 6c043fb..9c97b0c 100644
--- a/packages/salsa20/salsa20.bench.ts
+++ b/packages/salsa20/salsa20.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { streamXOR } from "./salsa20";
+import { streamXOR } from "./salsa20.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf8192 = byteSeq(8192);
diff --git a/packages/salsa20/salsa20.test.ts b/packages/salsa20/salsa20.test.ts
index 73248ad..361df5b 100644
--- a/packages/salsa20/salsa20.test.ts
+++ b/packages/salsa20/salsa20.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { streamXOR, stream } from "./salsa20";
+import { streamXOR, stream } from "./salsa20.js";
 import { encode, decode } from "@stablelib/hex";
 
 function seq(len: number): Uint8Array {
diff --git a/packages/scrypt/scrypt.bench.ts b/packages/scrypt/scrypt.bench.ts
index 26f14cd..7050520 100644
--- a/packages/scrypt/scrypt.bench.ts
+++ b/packages/scrypt/scrypt.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { deriveKey, deriveKeyNonBlocking, Scrypt } from "./scrypt";
+import { deriveKey, deriveKeyNonBlocking, Scrypt } from "./scrypt.js";
 import { benchmarkPromise, benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 (async () => {
diff --git a/packages/scrypt/scrypt.test.ts b/packages/scrypt/scrypt.test.ts
index b17e2ef..e4ddd12 100644
--- a/packages/scrypt/scrypt.test.ts
+++ b/packages/scrypt/scrypt.test.ts
@@ -4,7 +4,7 @@
 import { describe, expect, it } from 'vitest';
 import { encode as encodeBase64 } from "@stablelib/base64";
 import { encode as encodeUTF8 } from "@stablelib/utf8";
-import { deriveKey, deriveKeyNonBlocking } from "./scrypt";
+import { deriveKey, deriveKeyNonBlocking } from "./scrypt.js";
 
 const vectors = [
     {
diff --git a/packages/sha224/sha224.test.ts b/packages/sha224/sha224.test.ts
index 57bf3fb..d036480 100644
--- a/packages/sha224/sha224.test.ts
+++ b/packages/sha224/sha224.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { SHA224, hash } from "./sha224";
+import { SHA224, hash } from "./sha224.js";
 import { encode } from "@stablelib/base64";
 
 const vectors = [
diff --git a/packages/sha256/sha256.bench.ts b/packages/sha256/sha256.bench.ts
index 992905e..ecc0260 100644
--- a/packages/sha256/sha256.bench.ts
+++ b/packages/sha256/sha256.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { hash } from "./sha256";
+import { hash } from "./sha256.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 let buf1M = byteSeq(1024 << 10);
diff --git a/packages/sha256/sha256.test.ts b/packages/sha256/sha256.test.ts
index 0dd38c8..5d430a1 100644
--- a/packages/sha256/sha256.test.ts
+++ b/packages/sha256/sha256.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { SHA256, hash } from "./sha256";
+import { SHA256, hash } from "./sha256.js";
 import { encode } from "@stablelib/base64";
 
 const vectors = [
diff --git a/packages/sha3/sha3.bench.ts b/packages/sha3/sha3.bench.ts
index 5dbea0d..0143014 100644
--- a/packages/sha3/sha3.bench.ts
+++ b/packages/sha3/sha3.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { hash256 } from "./sha3";
+import { hash256 } from "./sha3.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 let buf1M = byteSeq(1024 << 10);
diff --git a/packages/sha3/sha3.test.ts b/packages/sha3/sha3.test.ts
index 174b31e..43d0c6e 100644
--- a/packages/sha3/sha3.test.ts
+++ b/packages/sha3/sha3.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { SHA3, SHA3256, SHAKE128, SHAKE256 } from "./sha3";
+import { SHA3, SHA3256, SHAKE128, SHAKE256 } from "./sha3.js";
 import { encode } from "@stablelib/base64";
 
 const vectors256 = [
diff --git a/packages/sha384/sha384.test.ts b/packages/sha384/sha384.test.ts
index f6e30a4..e23f6a0 100644
--- a/packages/sha384/sha384.test.ts
+++ b/packages/sha384/sha384.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { SHA384, hash } from "./sha384";
+import { SHA384, hash } from "./sha384.js";
 import { encode } from "@stablelib/base64";
 
 const vectors = [
diff --git a/packages/sha512/sha512.bench.ts b/packages/sha512/sha512.bench.ts
index 237d8ae..c52f620 100644
--- a/packages/sha512/sha512.bench.ts
+++ b/packages/sha512/sha512.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { hash } from "./sha512";
+import { hash } from "./sha512.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 let buf1M = byteSeq(1024 << 10);
diff --git a/packages/sha512/sha512.test.ts b/packages/sha512/sha512.test.ts
index a3d1f79..93f2b74 100644
--- a/packages/sha512/sha512.test.ts
+++ b/packages/sha512/sha512.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { SHA512, hash } from "./sha512";
+import { SHA512, hash } from "./sha512.js";
 import { encode } from "@stablelib/base64";
 
 const vectors = [
diff --git a/packages/sha512_256/sha512_256.test.ts b/packages/sha512_256/sha512_256.test.ts
index 4af2b42..7168bbc 100644
--- a/packages/sha512_256/sha512_256.test.ts
+++ b/packages/sha512_256/sha512_256.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { SHA512_256, hash } from "./sha512_256";
+import { SHA512_256, hash } from "./sha512_256.js";
 import { encode } from "@stablelib/base64";
 
 const vectors = [
diff --git a/packages/siv/siv.bench.ts b/packages/siv/siv.bench.ts
index 366ef57..582496b 100644
--- a/packages/siv/siv.bench.ts
+++ b/packages/siv/siv.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2017 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { SIV } from "./siv";
+import { SIV } from "./siv.js";
 import { AES } from "@stablelib/aes";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
diff --git a/packages/siv/siv.test.ts b/packages/siv/siv.test.ts
index 2b275e3..4f8c23a 100644
--- a/packages/siv/siv.test.ts
+++ b/packages/siv/siv.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { SIV } from "./siv";
+import { SIV } from "./siv.js";
 import { AES } from "@stablelib/aes";
 import { encode, decode } from "@stablelib/hex";
 import { byteSeq } from "@stablelib/benchmark";
diff --git a/packages/snappy/snappy.bench.ts b/packages/snappy/snappy.bench.ts
index 46a5681..a24a8c5 100644
--- a/packages/snappy/snappy.bench.ts
+++ b/packages/snappy/snappy.bench.ts
@@ -2,10 +2,10 @@
 // MIT License. See LICENSE file for details.
 
 import { benchmark, report } from "@stablelib/benchmark";
-import { compress, maxCompressedLength } from "./compress";
-import { decompress } from "./decompress";
+import { compress, maxCompressedLength } from "./compress.js";
+import { decompress } from "./decompress.js";
 import * as zlib from "zlib";
-import data from "./compress.test-data";
+import data from "./compress.test-data.js";
 
 
 const compressedData = compress(data);
diff --git a/packages/snappy/snappy.test.ts b/packages/snappy/snappy.test.ts
index 2cce9c6..35ef05a 100644
--- a/packages/snappy/snappy.test.ts
+++ b/packages/snappy/snappy.test.ts
@@ -5,9 +5,9 @@ import { describe, expect, it } from 'vitest';
 import * as utf8 from "@stablelib/utf8";
 import * as hex from "@stablelib/hex";
 import { byteSeq } from "@stablelib/benchmark";
-import { compress } from "./compress";
-import { decompress } from "./decompress";
-import bigTestData from "./compress.test-data";
+import { compress } from "./compress.js";
+import { decompress } from "./decompress.js";
+import bigTestData from "./compress.test-data.js";
 
 const smallTestData = utf8.encode("aaaaaaaaaabbabbbabbbabbabccccccccbbbbbbbaaaaaaabbabbabba");
 // generated with github.com/golang/snappy
diff --git a/packages/snappy/snappy.ts b/packages/snappy/snappy.ts
index 1a13994..e535fd0 100644
--- a/packages/snappy/snappy.ts
+++ b/packages/snappy/snappy.ts
@@ -11,5 +11,5 @@
  * Package snappy implements Snappy compression and decompression.
  */
 
-export * from "./compress";
-export * from "./decompress";
+export * from "./compress.js";
+export * from "./decompress.js";
diff --git a/packages/tss/tss.bench.ts b/packages/tss/tss.bench.ts
index 4455e14..5400bb2 100644
--- a/packages/tss/tss.bench.ts
+++ b/packages/tss/tss.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { splitRaw, combineRaw, split, combine } from "./tss";
+import { splitRaw, combineRaw, split, combine } from "./tss.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const secret = byteSeq(32);
diff --git a/packages/tss/tss.test.ts b/packages/tss/tss.test.ts
index a3e3d2b..84a10ef 100644
--- a/packages/tss/tss.test.ts
+++ b/packages/tss/tss.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { split, combine, combineRaw } from "./tss";
+import { split, combine, combineRaw } from "./tss.js";
 import { decode } from "@stablelib/hex";
 
 describe("tss", () => {
diff --git a/packages/utf8/utf8.bench.ts b/packages/utf8/utf8.bench.ts
index 9b914a6..c78cbab 100644
--- a/packages/utf8/utf8.bench.ts
+++ b/packages/utf8/utf8.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { encode, decode } from "./utf8";
+import { encode, decode } from "./utf8.js";
 import { benchmark, report } from "@stablelib/benchmark";
 
 const text = `— Еh bien, mon prince. Gênes et Lucques ne sont plus que des apanages,
diff --git a/packages/utf8/utf8.test.ts b/packages/utf8/utf8.test.ts
index ce6142b..3c0b962 100644
--- a/packages/utf8/utf8.test.ts
+++ b/packages/utf8/utf8.test.ts
@@ -3,7 +3,7 @@
 
 import { describe, expect, it } from 'vitest';
 import * as hex from "@stablelib/hex";
-import { encode, decode } from "./utf8";
+import { encode, decode } from "./utf8.js";
 
 describe("utf8", () => {
     it("should encode and decode strings", () => {
diff --git a/packages/uuid/uuid.test.ts b/packages/uuid/uuid.test.ts
index db44d05..781a1a0 100644
--- a/packages/uuid/uuid.test.ts
+++ b/packages/uuid/uuid.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { uuid } from "./uuid";
+import { uuid } from "./uuid.js";
 
 describe("uuid", () => {
     it("should generate UUID", () => {
diff --git a/packages/wipe/wipe.test.ts b/packages/wipe/wipe.test.ts
index 2432cbe..4cc9806 100644
--- a/packages/wipe/wipe.test.ts
+++ b/packages/wipe/wipe.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { wipe } from "./wipe";
+import { wipe } from "./wipe.js";
 
 describe("wipe", () => {
     it("should wipe bytes", () => {
diff --git a/packages/x25519-session/keyagreement.ts b/packages/x25519-session/keyagreement.ts
index d5e4561..afc1b02 100644
--- a/packages/x25519-session/keyagreement.ts
+++ b/packages/x25519-session/keyagreement.ts
@@ -12,8 +12,8 @@ import { PUBLIC_KEY_LENGTH,
     SHARED_KEY_LENGTH,
     generateKeyPairFromSeed,
     sharedKey } from "@stablelib/x25519";
-import type { SessionKeys} from "./x25519-session";
-import { clientSessionKeysFromSharedKey, serverSessionKeysFromSharedKey } from "./x25519-session";
+import type { SessionKeys} from "./x25519-session.js";
+import { clientSessionKeysFromSharedKey, serverSessionKeysFromSharedKey } from "./x25519-session.js";
 
 /** Constants for key agreement */
 export const OFFER_MESSAGE_LENGTH = PUBLIC_KEY_LENGTH;
diff --git a/packages/x25519-session/x25519-session.bench.ts b/packages/x25519-session/x25519-session.bench.ts
index 20e39d7..14c7dd2 100644
--- a/packages/x25519-session/x25519-session.bench.ts
+++ b/packages/x25519-session/x25519-session.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { X25519Session } from "./keyagreement";
+import { X25519Session } from "./keyagreement.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const r = new Uint8Array(32); r[0] = 1;
diff --git a/packages/x25519-session/x25519-session.test.ts b/packages/x25519-session/x25519-session.test.ts
index 6d8f6d9..e5424e4 100644
--- a/packages/x25519-session/x25519-session.test.ts
+++ b/packages/x25519-session/x25519-session.test.ts
@@ -4,7 +4,7 @@
 import { describe, expect, it } from 'vitest';
 import type { RandomSource } from "@stablelib/random";
 import { encode } from "@stablelib/hex";
-import { X25519Session } from './keyagreement';
+import { X25519Session } from './keyagreement.js';
 
 // For testing with generated test vectors, instead of proper PRNG
 // use the deterministic generator that generates byte sequences
diff --git a/packages/x25519-session/x25519-session.ts b/packages/x25519-session/x25519-session.ts
index 0f1bba4..8927cf8 100644
--- a/packages/x25519-session/x25519-session.ts
+++ b/packages/x25519-session/x25519-session.ts
@@ -9,7 +9,7 @@ import { BLAKE2b } from "@stablelib/blake2b";
 import type { Hash } from "@stablelib/hash";
 import type { KeyPair } from "@stablelib/x25519";
 import { sharedKey as deriveSharedKey } from "@stablelib/x25519";
-export { X25519Session } from "./keyagreement";
+export { X25519Session } from "./keyagreement.js";
 
 const SESSION_KEY_LENGTH = 32;
 
diff --git a/packages/x25519/keyagreement.ts b/packages/x25519/keyagreement.ts
index 4b6eb41..8c0d26f 100644
--- a/packages/x25519/keyagreement.ts
+++ b/packages/x25519/keyagreement.ts
@@ -5,7 +5,7 @@ import type { KeyAgreement } from "@stablelib/keyagreement";
 import type { RandomSource } from "@stablelib/random";
 import { randomBytes } from "@stablelib/random";
 import { wipe } from "@stablelib/wipe";
-import { PUBLIC_KEY_LENGTH, SECRET_KEY_LENGTH, SHARED_KEY_LENGTH, generateKeyPairFromSeed, sharedKey } from "./x25519";
+import { PUBLIC_KEY_LENGTH, SECRET_KEY_LENGTH, SHARED_KEY_LENGTH, generateKeyPairFromSeed, sharedKey } from "./x25519.js";
 
 /** Constants for key agreement */
 export const OFFER_MESSAGE_LENGTH = PUBLIC_KEY_LENGTH;
diff --git a/packages/x25519/x25519.bench.ts b/packages/x25519/x25519.bench.ts
index e8f5e10..973bd19 100644
--- a/packages/x25519/x25519.bench.ts
+++ b/packages/x25519/x25519.bench.ts
@@ -1,8 +1,8 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { scalarMultBase } from "./x25519";
-import { X25519KeyAgreement } from "./keyagreement";
+import { scalarMultBase } from "./x25519.js";
+import { X25519KeyAgreement } from "./keyagreement.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const r = new Uint8Array(32); r[0] = 1;
diff --git a/packages/x25519/x25519.test.ts b/packages/x25519/x25519.test.ts
index aad7318..ed65b48 100644
--- a/packages/x25519/x25519.test.ts
+++ b/packages/x25519/x25519.test.ts
@@ -6,8 +6,8 @@ import type { RandomSource } from "@stablelib/random";
 import { encode, decode } from "@stablelib/hex";
 import {
     scalarMultBase, sharedKey, generateKeyPair
-} from "./x25519";
-import { X25519KeyAgreement } from './keyagreement';
+} from "./x25519.js";
+import { X25519KeyAgreement } from './keyagreement.js';
 
 describe("x25519.scalarMultBase", () => {
     it("should return correct result", () => {
diff --git a/packages/xchacha20/xchacha20.bench.ts b/packages/xchacha20/xchacha20.bench.ts
index e6dd68d..48e7aa7 100644
--- a/packages/xchacha20/xchacha20.bench.ts
+++ b/packages/xchacha20/xchacha20.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { streamXOR } from "./xchacha20";
+import { streamXOR } from "./xchacha20.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf16K = byteSeq(16 << 10);
diff --git a/packages/xchacha20/xchacha20.test.ts b/packages/xchacha20/xchacha20.test.ts
index 16d6842..4ce50a1 100644
--- a/packages/xchacha20/xchacha20.test.ts
+++ b/packages/xchacha20/xchacha20.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { hchacha, stream, streamXOR } from "./xchacha20";
+import { hchacha, stream, streamXOR } from "./xchacha20.js";
 import { encode, decode } from "@stablelib/hex";
 
 // test taken from draft-arciszewski-xchacha-03 section 2.2.1
diff --git a/packages/xchacha20poly1305/xchacha20poly1305.bench.ts b/packages/xchacha20poly1305/xchacha20poly1305.bench.ts
index f2e241d..23da92f 100644
--- a/packages/xchacha20poly1305/xchacha20poly1305.bench.ts
+++ b/packages/xchacha20poly1305/xchacha20poly1305.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { XChaCha20Poly1305 } from "./xchacha20poly1305";
+import { XChaCha20Poly1305 } from "./xchacha20poly1305.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf8192 = byteSeq(8192);
diff --git a/packages/xchacha20poly1305/xchacha20poly1305.test.ts b/packages/xchacha20poly1305/xchacha20poly1305.test.ts
index 0f7e9a3..4993402 100644
--- a/packages/xchacha20poly1305/xchacha20poly1305.test.ts
+++ b/packages/xchacha20poly1305/xchacha20poly1305.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { XChaCha20Poly1305 } from "./xchacha20poly1305";
+import { XChaCha20Poly1305 } from "./xchacha20poly1305.js";
 import { encode, decode } from "@stablelib/hex";
 
 const testVectors = [
diff --git a/packages/xsalsa20/xsalsa20.bench.ts b/packages/xsalsa20/xsalsa20.bench.ts
index aceea7c..0e723d5 100644
--- a/packages/xsalsa20/xsalsa20.bench.ts
+++ b/packages/xsalsa20/xsalsa20.bench.ts
@@ -1,7 +1,7 @@
 // Copyright (C) 2016 Dmitry Chestnykh
 // MIT License. See LICENSE file for details.
 
-import { streamXOR } from "./xsalsa20";
+import { streamXOR } from "./xsalsa20.js";
 import { benchmark, report, byteSeq } from "@stablelib/benchmark";
 
 const buf8192 = byteSeq(8192);
diff --git a/packages/xsalsa20/xsalsa20.test.ts b/packages/xsalsa20/xsalsa20.test.ts
index 680ac3d..e81d704 100644
--- a/packages/xsalsa20/xsalsa20.test.ts
+++ b/packages/xsalsa20/xsalsa20.test.ts
@@ -2,7 +2,7 @@
 // MIT License. See LICENSE file for details.
 
 import { describe, expect, it } from 'vitest';
-import { stream, hsalsa } from "./xsalsa20";
+import { stream, hsalsa } from "./xsalsa20.js";
 import { encode, decode } from "@stablelib/hex";
 
 describe("xsalsa20.hsalsa", () => {