diff --git a/localtypings/pxteditor.d.ts b/localtypings/pxteditor.d.ts
index 89849714e1fc..f4741c95c3f4 100644
--- a/localtypings/pxteditor.d.ts
+++ b/localtypings/pxteditor.d.ts
@@ -914,7 +914,7 @@ declare namespace pxt.editor {
         forceUpdate(): void;
 
         reloadEditor(): void;
-        openBlocks(): void;
+        openBlocks(showKeyboardControlsHint?: boolean): void;
         openJavaScript(giveFocusOnLoading?: boolean): void;
         openPython(giveFocusOnLoading?: boolean): void;
         openAssets(): void;
diff --git a/pxtlib/auth.ts b/pxtlib/auth.ts
index 5e9987c01c29..9e34f509d115 100644
--- a/pxtlib/auth.ts
+++ b/pxtlib/auth.ts
@@ -73,7 +73,7 @@ namespace pxt.auth {
     export const DEFAULT_USER_PREFERENCES: () => UserPreferences = () => ({
         language: pxt.appTarget.appTheme.defaultLocale,
         highContrast: false,
-        accessibleBlocks: false,
+        accessibleBlocks: undefined, // Defaulted at read time depending on flag
         colorThemeIds: {}, // Will lookup pxt.appTarget.appTheme.defaultColorTheme for active target
         reader: "",
         skillmap: { mapProgress: {}, completedTags: {} },
diff --git a/webapp/src/accessibility.tsx b/webapp/src/accessibility.tsx
index 383e7fab3c07..04220036d351 100644
--- a/webapp/src/accessibility.tsx
+++ b/webapp/src/accessibility.tsx
@@ -2,6 +2,7 @@
 
 import * as React from "react";
 import * as auth from "./auth";
+import * as core from "./core";
 import * as data from "./data";
 import * as sui from "./sui";
 
@@ -34,7 +35,7 @@ export class EditorAccessibilityMenu extends data.Component<EditorAccessibilityM
     }
 
     openBlocks(e: React.MouseEvent<HTMLElement>) {
-        this.props.parent.openBlocks();
+        this.props.parent.openBlocks(core.isKeyboardControlsByDefault());
     }
 
     openJavaScript() {
diff --git a/webapp/src/app.tsx b/webapp/src/app.tsx
index 20b3fed7bd34..07493286ad28 100644
--- a/webapp/src/app.tsx
+++ b/webapp/src/app.tsx
@@ -716,9 +716,13 @@ export class ProjectView
         pxt.shell.setEditorLanguagePref("js");
     }
 
-    openBlocks() {
+    openBlocks(showKeyboardControlsHint?: boolean) {
         if (this.updatingEditorFile) return; // already transitioning
 
+        if (showKeyboardControlsHint) {
+            this.blocksEditor.pendingKeyboardControlsHint = true;
+        }
+
         if (this.isBlocksActive()) {
             if (this.state.embedSimView) this.setState({ embedSimView: false });
             // This timeout prevents key events from being handled by Blockly's keyboard
diff --git a/webapp/src/auth.ts b/webapp/src/auth.ts
index 14110ed00de1..cd7f810641c5 100644
--- a/webapp/src/auth.ts
+++ b/webapp/src/auth.ts
@@ -117,7 +117,11 @@ class AuthClient extends pxt.auth.AuthClient {
             // Identity not available, read from local storage
             switch (path) {
                 case HIGHCONTRAST: return /^true$/i.test(pxt.storage.getLocal(HIGHCONTRAST));
-                case ACCESSIBLE_BLOCKS: return /^true$/i.test(pxt.storage.getLocal(ACCESSIBLE_BLOCKS));
+                case ACCESSIBLE_BLOCKS: {
+                    const stored = pxt.storage.getLocal(ACCESSIBLE_BLOCKS);
+                    if (stored == null) return core.isKeyboardControlsByDefault();
+                    return /^true$/i.test(stored);
+                }
                 case COLOR_THEME_IDS: return pxt.U.jsonTryParse(pxt.storage.getLocal(COLOR_THEME_IDS)) as pxt.auth.ColorThemeIdsState;
                 case LANGUAGE: return pxt.storage.getLocal(LANGUAGE);
                 case READER: return pxt.storage.getLocal(READER);
@@ -134,7 +138,7 @@ class AuthClient extends pxt.auth.AuthClient {
             switch (field) {
                 case FIELD_USER_PREFERENCES: return { ...state.preferences };
                 case FIELD_HIGHCONTRAST: return state.preferences?.highContrast ?? pxt.auth.DEFAULT_USER_PREFERENCES().highContrast;
-                case FIELD_KEYBOARD_CONTROLS: return state.preferences?.accessibleBlocks ?? pxt.auth.DEFAULT_USER_PREFERENCES().accessibleBlocks;
+                case FIELD_KEYBOARD_CONTROLS: return state.preferences?.accessibleBlocks ?? core.isKeyboardControlsByDefault();
                 case FIELD_COLOR_THEME_IDS: return state.preferences?.colorThemeIds ?? pxt.auth.DEFAULT_USER_PREFERENCES().colorThemeIds;
                 case FIELD_LANGUAGE: return state.preferences?.language ?? pxt.auth.DEFAULT_USER_PREFERENCES().language;
                 case FIELD_READER: return state.preferences?.reader ?? pxt.auth.DEFAULT_USER_PREFERENCES().reader;
@@ -250,6 +254,7 @@ export async function setAccessibleBlocksPrefAsync(accessibleBlocks: boolean, ev
         "auth.setAccessibleBlocks",
         {
             enabling: accessibleBlocks ? "true" : "false",
+            defaultOn: core.isKeyboardControlsByDefault() ? "true" : "false",
             eventSource: eventSource,
             local: !cli ? "true" : "false"
         }
diff --git a/webapp/src/blocks.tsx b/webapp/src/blocks.tsx
index 47b1eb56ba02..1c1900ab5cfd 100644
--- a/webapp/src/blocks.tsx
+++ b/webapp/src/blocks.tsx
@@ -59,6 +59,7 @@ export class Editor extends toolboxeditor.ToolboxEditor {
     loadingXmlPromise: Promise<any>;
     compilationResult: pxtblockly.BlockCompilationResult;
     shouldFocusWorkspace = false;
+    pendingKeyboardControlsHint = false;
     functionsDialog: CreateFunctionDialog = null;
 
     showCategories: boolean = true;
@@ -997,9 +998,21 @@ export class Editor extends toolboxeditor.ToolboxEditor {
         if (accessibleBlocksEnabled) {
             (this.editor.getSvgGroup() as SVGElement).focus();
             Blockly.hideChaff();
+
+            if (this.pendingKeyboardControlsHint) {
+                this.pendingKeyboardControlsHint = false;
+                this.showKeyboardControlsHint();
+            }
         }
     }
 
+    showKeyboardControlsHint() {
+        if (!this.editor || !Blockly.Msg["HELP_PROMPT"]) return;
+        const shortcut = pxt.BrowserUtils.isMac() ? "⌘ /" : lf("Ctrl") + " + /";
+        const message = Blockly.Msg["HELP_PROMPT"].replace("%1", shortcut);
+        Blockly.Toast.show(this.editor, { message, id: "helpHint", oncePerSession: true });
+    }
+
     hasUndo() {
         const undoStack = this.editor?.getUndoStack();
         const redoStack = this.editor?.getRedoStack();
diff --git a/webapp/src/core.ts b/webapp/src/core.ts
index ca2afb6b34f1..6c5fe17155ec 100644
--- a/webapp/src/core.ts
+++ b/webapp/src/core.ts
@@ -343,6 +343,13 @@ export function getHighContrastOnce(): boolean {
     return ThemeManager.isCurrentThemeHighContrast();
 }
 
+/**
+ * Returns true if keyboard controls should be enabled by default.
+ */
+export function isKeyboardControlsByDefault(): boolean {
+    return /keyboardcontrols=1/i.test(window.location.href);
+}
+
 export async function toggleAccessibleBlocks(eventSource: string) {
     await setAccessibleBlocks(!data.getData<boolean>(auth.ACCESSIBLE_BLOCKS), eventSource);
 }