diff --git a/js/Cargo.lock b/js/Cargo.lock
index 72123f92..a41a5964 100644
--- a/js/Cargo.lock
+++ b/js/Cargo.lock
@@ -4,15 +4,14 @@ version = 4
 
 [[package]]
 name = "adblock"
-version = "0.9.5"
+version = "0.9.6"
 dependencies = [
  "addr",
  "base64",
- "bitflags",
+ "bitflags 2.9.0",
  "cssparser",
  "idna",
  "itertools",
- "lifeguard",
  "memchr",
  "once_cell",
  "percent-encoding",
@@ -63,9 +62,9 @@ checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
 [[package]]
 name = "base64"
-version = "0.13.0"
+version = "0.22.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"
+checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
 
 [[package]]
 name = "bitflags"
@@ -73,6 +72,15 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
+[[package]]
+name = "bitflags"
+version = "2.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c8214115b7bf84099f1309324e63141d4c5d7cc26862f97a0a857dbefe165bd"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "byteorder"
 version = "1.4.3"
@@ -362,12 +370,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "lifeguard"
-version = "0.6.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "89be94dbd775db37b46ca4f4bf5cf89adfb13ba197bfbcb69b2122848ee73c26"
-
 [[package]]
 name = "litemap"
 version = "0.7.4"
@@ -674,9 +676,9 @@ checksum = "71d301d4193d031abdd79ff7e3dd721168a9572ef3fe51a1517aba235bd8f86e"
 
 [[package]]
 name = "seahash"
-version = "3.0.6"
+version = "4.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "18d6061ff4917fac173fa07b839c8c3f805c0bf3801c52499cc85cdbad8c28df"
+checksum = "1c107b6f4780854c8b126e228ea8869f4d7b71260f962fefb57b996b8959ba6b"
 
 [[package]]
 name = "selectors"
@@ -684,7 +686,7 @@ version = "0.24.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0c37578180969d00692904465fb7f6b3d50b9a2b952b87c23d0e2e5cb5013416"
 dependencies = [
- "bitflags",
+ "bitflags 1.3.2",
  "cssparser",
  "derive_more",
  "fxhash",
diff --git a/js/check.js b/js/check.js
new file mode 100755
index 00000000..521352ac
--- /dev/null
+++ b/js/check.js
@@ -0,0 +1,231 @@
+#!/usr/bin/env node
+
+const { text } = require('node:stream/consumers')
+const readline = require('node:readline')
+const fs = require('node:fs')
+
+const { ArgumentParser, FileType } = require('argparse')
+
+const adblockRust = require('./index.js')
+const adblockRustPackage = require('./../package.json')
+
+// These are defined by different content filter projects (AdBlock Plus,
+// uBlockOrigin, AdGuard, etc.).
+// For example, https://github.com/gorhill/uBlock/wiki/Static-filter-syntax
+const filterListRequestTypes = [
+  'beacon',
+  'csp_report',
+  'document',
+  'font',
+  'image',
+  'media',
+  'object',
+  'ping',
+  'script',
+  'stylesheet',
+  'sub_frame',
+  'websocket',
+  'xhr',
+  'other',
+  'speculative',
+  'web_manifest',
+  'xbl',
+  'xml_dtd',
+  'xslt'
+]
+
+// These values are defined by Blink, in `Resource::ResourceTypeToString`.
+// See third_party/blink/renderer/platform/loader/fetch/resource.h.
+// The OTHER catch all case covers the additional types
+// defined in `blink::Resource::InitiatorTypeNameToString`.
+//
+// See https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/platform/loader/fetch/resource.cc
+/* eslint-disable quote-props */
+const chromiumRequestTypeMapping = {
+  'Attribution resource': 'other',
+  'Audio': 'media',
+  'CSS resource': 'stylesheet',
+  'CSS stylesheet': 'stylesheet',
+  'Dictionary': 'other',
+  'Document': 'document',
+  'Fetch': 'xhr',
+  'Font': 'font',
+  'Icon': 'other',
+  'Image': 'image',
+  'Internal resource': 'other',
+  'Link element resource': 'other',
+  'Link prefetch resource': 'speculative',
+  'Manifest': 'web_manifest',
+  'Mock': 'other',
+  'Other resource': 'other',
+  'Processing instruction': 'other',
+  'Script': 'script',
+  'SpeculationRule': 'speculative',
+  'SVG document': 'media',
+  'SVG Use element resource': 'media',
+  'Text track': 'other',
+  'Track': 'other',
+  'User Agent CSS resource': 'stylesheet',
+  'Video': 'media',
+  'XML resource': 'document',
+  'XMLHttpRequest': 'xhr',
+  'XSL stylesheet': 'xslt'
+}
+/* eslint-enable quote-props */
+const chromiumRequestTypes = Object.keys(chromiumRequestTypeMapping)
+const requestTypeOptions = filterListRequestTypes.concat(chromiumRequestTypes)
+requestTypeOptions.sort()
+
+const parser = new ArgumentParser({
+  add_help: true,
+  description: 'Check whether a URL would be blocked by given filter list rules'
+})
+parser.add_argument('-v', '--version', {
+  action: 'version',
+  version: adblockRustPackage.version
+})
+
+parser.add_argument('--requests', {
+  type: FileType('r'),
+  default: process.stdin,
+  help: 'Path to a file of requests to check filter list rules against (or, ' +
+        'by default, STDIN). This input should be lines of JSON documents, ' +
+        'one document per line. This JSON text must have the following keys: ' +
+        '"url", "context", and "type", which corresponds to the --url, ' +
+        '--context, and --type arguments.'
+})
+
+parser.add_argument('--url', {
+  type: URL,
+  help: 'The full URL to check against the provided filter lists.'
+})
+parser.add_argument('--context', {
+  type: URL,
+  help: 'The security context the request occurred in, as a full URL'
+})
+parser.add_argument('--type', {
+  help: 'The type of the request, using either i. the types defined by ' +
+        'filter list projects (which are all in lowercase, e.g., "xhr" or ' +
+        '"stylesheet"), or ii. the types defined in the Chromium source ' +
+        '(which start with an uppercase character, e.g., "XMLHttpRequest" or ' +
+        '"CSS stylesheet")',
+  choices: requestTypeOptions
+})
+
+parser.add_argument('--rules', {
+  type: FileType('r'),
+  nargs: '*',
+  help: 'One or more paths to files of filter list rules to check the ' +
+        'request against. By default uses bundled old-and-outdated versions ' +
+        'of easylist and easyprivacy'
+})
+parser.add_argument('--verbose', {
+  default: false,
+  action: 'store_true',
+  help: 'Print information about what rule(s) the request matched.'
+})
+
+const checkRequest = (engine, request, requestType, requestContext) => {
+  const requestTypeUnified = chromiumRequestTypeMapping[requestType] || requestType
+  try {
+    return engine.check(
+      request.toString(),
+      requestContext.toString(),
+      requestTypeUnified,
+      true
+    )
+  } catch (e) {
+    console.error(`Error checking request: url:${request}, ` +
+                  `context:${requestContext}, type:${requestTypeUnified}`)
+    console.error('adblock-rust error: ' + e.toString())
+    return null
+  }
+}
+
+;(async () => {
+  const args = parser.parse_args()
+
+  const filterSet = new adblockRust.FilterSet(true)
+  let ruleStreams
+  if (args.rules) {
+    ruleStreams = args.rules
+  } else {
+    const defaultLists = [
+      './data/easylist.to/easylist/easylist.txt',
+      './data/easylist.to/easylist/easyprivacy.txt'
+    ]
+    ruleStreams = defaultLists.map((x) => fs.createReadStream(x, {}))
+  }
+
+  for (const aRuleStream of ruleStreams) {
+    const rulesText = await text(aRuleStream)
+    filterSet.addFilters(rulesText.split('\n'))
+  }
+
+  const engine = new adblockRust.Engine(filterSet, true)
+  const checkRequestFunc = checkRequest.bind(undefined, engine)
+
+  // This code can either be invoked to consider one request, using command
+  // line flags, or read request descriptions from a handle. If
+  // any of the following arguments were provided, then we assume we're in
+  // "arguments" mode, otherwise we stream request descriptions from the
+  // --requests argument.
+  const requestDescArgs = ['url', 'context', 'type']
+  const numRequestDescArgs = requestDescArgs.reduce((accumulator, curValue) => {
+    return (args[curValue] !== undefined) ? accumulator + 1 : accumulator
+  }, 0)
+  const isReadingRequestFromArgs = (numRequestDescArgs > 0)
+
+  if (isReadingRequestFromArgs) {
+    if (numRequestDescArgs < requestDescArgs.length) {
+      throw new Error(
+        '--url, --context, and --type must be either all provided, or none of ' +
+        'them provided.')
+    }
+    const result = checkRequestFunc(args.url, args.type, args.context)
+    if (result === null) {
+      process.exit(1)
+    }
+    const resultMatched = result.matched
+    console.log(args.verbose ? result : resultMatched)
+    process.exit(0)
+  }
+
+  // Otherwise, we're in "streaming" mode, and we read requests off whatever
+  // was provided in --requests (which is either the path to a file, or
+  // stdin).
+  const readlineInterface = readline.createInterface({
+    input: args.requests,
+    terminal: false
+  })
+  let anyErrors = false
+  readlineInterface.on('line', (line) => {
+    let requestData
+    try {
+      requestData = JSON.parse(line)
+    } catch (e) {
+      const msg = 'Invalid JSON in requests input: ' + line
+      throw new Error(msg)
+    }
+
+    if (requestData.url === undefined ||
+        requestData.type === undefined ||
+        requestData.context === undefined) {
+      throw new Error('Request description does not include all three ' +
+                      'required keys, "url", "type", "context".\n' + line)
+    }
+
+    const result = checkRequestFunc(
+      requestData.url, requestData.type, requestData.context)
+    if (result === null) {
+      anyErrors = true
+    } else {
+      const resultMatched = result.matched
+      console.log(args.verbose ? JSON.stringify(result) : resultMatched)
+    }
+  })
+
+  readlineInterface.on('close', () => {
+    process.exit(anyErrors === true ? 1 : 0)
+  })
+})()
diff --git a/package-lock.json b/package-lock.json
index 7fab6f91..f624906a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -10,9 +10,15 @@
       "hasInstallScript": true,
       "license": "MPL-2.0",
       "dependencies": {
+        "argparse": "^2.0.1",
         "cargo-cp-artifact": "^0.1"
       }
     },
+    "node_modules/argparse": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/argparse/-/argparse-2.0.1.tgz",
+      "integrity": "sha512-8+9WqebbFzpX9OR+Wa6O29asIogeRMzcGtAINdpMHHyAg10f05aSFVBbcEqGf/PXw1EjAZ+q2/bEBg3DvurK3Q=="
+    },
     "node_modules/cargo-cp-artifact": {
       "version": "0.1.9",
       "resolved": "https://registry.npmjs.org/cargo-cp-artifact/-/cargo-cp-artifact-0.1.9.tgz",
@@ -23,6 +29,11 @@
     }
   },
   "dependencies": {
+    "argparse": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/argparse/-/argparse-2.0.1.tgz",
+      "integrity": "sha512-8+9WqebbFzpX9OR+Wa6O29asIogeRMzcGtAINdpMHHyAg10f05aSFVBbcEqGf/PXw1EjAZ+q2/bEBg3DvurK3Q=="
+    },
     "cargo-cp-artifact": {
       "version": "0.1.9",
       "resolved": "https://registry.npmjs.org/cargo-cp-artifact/-/cargo-cp-artifact-0.1.9.tgz",
diff --git a/package.json b/package.json
index 53d450fd..d89e51a5 100644
--- a/package.json
+++ b/package.json
@@ -28,12 +28,14 @@
     "url": "git+https://github.com/brave/adblock-rust.git"
   },
   "dependencies": {
+    "argparse": "^2.0.1",
     "cargo-cp-artifact": "^0.1"
   },
   "scripts": {
     "build": "cd js && cargo-cp-artifact -nc index.node -- cargo build --message-format=json-render-diagnostics",
     "build-debug": "npm run build --",
     "build-release": "npm run build -- --release",
+    "check": "node ./js/check.js",
     "update-lists": "node data/update-lists.js",
     "postinstall": "npm run build-release",
     "test": "cargo test"