diff --git a/pxtblocks/blocklyloader.ts b/pxtblocks/blocklyloader.ts
index e851855aeffe..cd243e0f25ef 100644
--- a/pxtblocks/blocklyloader.ts
+++ b/pxtblocks/blocklyloader.ts
@@ -716,7 +716,8 @@ namespace pxt.blocks {
         block.setPreviousStatement(!(hasHandlers && !fn.attributes.handlerStatement) && fn.retType == "void");
         block.setNextStatement(!(hasHandlers && !fn.attributes.handlerStatement) && fn.retType == "void");
 
-        block.setTooltip(/^__/.test(fn.namespace) ? "" : fn.attributes.jsDoc);
+        block.setTooltip((/^__/.test(fn.namespace) ? "" : fn.attributes.jsDoc) + (pxt.blocks.showBlockIdInTooltip ? " (id: '" + fn.attributes.blockId + "')" : ""));
+
         function buildBlockFromDef(def: pxtc.ParsedBlockDef, expanded = false) {
             let anonIndex = 0;
             let firstParam = !expanded && !!comp.thisParameter;
diff --git a/pxtlib/blocks.ts b/pxtlib/blocks.ts
index c952112c4ba9..f1752e54d49f 100644
--- a/pxtlib/blocks.ts
+++ b/pxtlib/blocks.ts
@@ -3,6 +3,8 @@
 namespace pxt.blocks {
     const THIS_NAME = "this";
 
+    export let showBlockIdInTooltip: boolean = false;
+
     // The JS Math functions supported in the blocks. The order of this array
     // determines the order of the dropdown in the math_js_op block
     export const MATH_FUNCTIONS = {
@@ -806,5 +808,20 @@ namespace pxt.blocks {
                 )
             })
         }
+
+        if (pxt.blocks.showBlockIdInTooltip) {
+            for (const id of Object.keys(_blockDefinitions)) {
+                const tooltip = _blockDefinitions[id].tooltip;
+                if (typeof tooltip === "object" && tooltip !== null) {
+                    for (const innerKey in tooltip) {
+                        if (tooltip.hasOwnProperty(innerKey)) {
+                            (_blockDefinitions[id].tooltip as any)[innerKey] = `${tooltip[innerKey]} (id: ${id})`;
+                        }
+                    }
+                } else {
+                    _blockDefinitions[id].tooltip = `${_blockDefinitions[id].tooltip} (id: ${id})`;
+                }
+            }
+        }
     }
 }
diff --git a/webapp/src/app.tsx b/webapp/src/app.tsx
index 94bf1cb9f79e..1d2080c4f51a 100644
--- a/webapp/src/app.tsx
+++ b/webapp/src/app.tsx
@@ -5750,6 +5750,9 @@ document.addEventListener("DOMContentLoaded", async () => {
     } else if (optsQuery["consoleticks"] == "2" || optsQuery["consoleticks"] == "short") {
         pxt.analytics.consoleTicks = pxt.analytics.ConsoleTickOptions.Short;
     }
+    if (optsQuery["tooltipblockids"] == "1") {
+        pxt.blocks.showBlockIdInTooltip = true;
+    }
 
     initGitHubDb();