diff --git a/.env.example b/.env.example
index 223b92b7..f823652e 100644
--- a/.env.example
+++ b/.env.example
@@ -1,3 +1,3 @@
-# No public build-time variables are required. The app reads no VITE_* keys at
-# build time; the former Supabase and voting/Turnstile configuration was removed
-# when the request catalog and protected voting were retired.
+# Public PostHog browser configuration. Copy these values into a local .env file.
+VITE_POSTHOG_KEY=
+VITE_POSTHOG_HOST=
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 306c0e58..09224bbe 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -51,6 +51,7 @@ jobs:
             "@openmouse/keyboard-protocol": keyboardProtocolVersion,
             "@openmouse/protocol": protocolVersion,
             "lucide-react": "^1.43.0",
+            "posthog-js": "^1.438.17",
             "preact": "^10.29.8",
           };
 
diff --git a/build/check-bundle-size.ts b/build/check-bundle-size.ts
index ff234cf3..3c1644e1 100644
--- a/build/check-bundle-size.ts
+++ b/build/check-bundle-size.ts
@@ -1,9 +1,11 @@
 import { readdirSync, statSync } from "node:fs";
 import { join } from "node:path";
 
+// JS raised from 2_800_000: posthog-js (anonymous analytics, src/platform/analytics.ts)
+// added about 340 kB; measured 3_125_781 bytes with it.
 const BUDGET_BYTES: Record<string, number> = {
   ".css": 165_000,
-  ".js": 2_800_000,
+  ".js": 3_150_000,
 };
 
 const ASSETS = join("dist", "assets");
diff --git a/functions/_lib/security-headers.js b/functions/_lib/security-headers.js
index 2e9a6af1..51259e56 100644
--- a/functions/_lib/security-headers.js
+++ b/functions/_lib/security-headers.js
@@ -22,14 +22,14 @@
 
 export const CSP = [
   "default-src 'self'",
-  "script-src 'self'",
+  "script-src 'self' https://us-assets.i.posthog.com",
   "script-src-attr 'none'",
   "style-src 'self' https://fonts.googleapis.com",
   "style-src-attr 'none'",
   "font-src 'self' data: https://fonts.gstatic.com",
   "img-src 'self' data: blob: https://img.openmouse.app https://cdn.cloudflare.steamstatic.com https://shared.akamai.steamstatic.com https://store-images.s-microsoft.com http://127.0.0.1:17846",
   "media-src 'self'",
-  "connect-src 'self' https://api.github.com https://cdn.jsdelivr.net http://127.0.0.1:17846 ws://127.0.0.1:17846",
+  "connect-src 'self' https://us.i.posthog.com https://us-assets.i.posthog.com https://api.github.com https://cdn.jsdelivr.net http://127.0.0.1:17846 ws://127.0.0.1:17846",
   "worker-src 'self'",
   "manifest-src 'self'",
   "object-src 'none'",
diff --git a/package-lock.json b/package-lock.json
index e41a201b..43e1251d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,6 +12,7 @@
         "@openmouse/keyboard-protocol": "1.1.0",
         "@openmouse/protocol": "0.45.2",
         "lucide-react": "^1.43.0",
+        "posthog-js": "^1.438.17",
         "preact": "^10.29.8"
       },
       "devDependencies": {
@@ -499,6 +500,32 @@
         "node": ">=20"
       }
     },
+    "node_modules/@posthog/browser-common": {
+      "version": "0.9.8",
+      "resolved": "https://registry.npmjs.org/@posthog/browser-common/-/browser-common-0.9.8.tgz",
+      "integrity": "sha512-4+sQauvPkGfjQrz9whDCzV5I9wI9UTajIjukpRENhULP1a/uYyNR/LAa4CuX8XuIogtVpAYc+7iIZymwNSTOSA==",
+      "license": "MIT",
+      "dependencies": {
+        "@posthog/core": "^1.59.4",
+        "@posthog/types": "^1.416.0",
+        "preact": "^10.29.3"
+      }
+    },
+    "node_modules/@posthog/core": {
+      "version": "1.60.0",
+      "resolved": "https://registry.npmjs.org/@posthog/core/-/core-1.60.0.tgz",
+      "integrity": "sha512-d8jmcvJPmgjkcW0kVbIkDXcD3jJ+y/wS6oA4PeEGL914Rj8iM9HfB6VWvMWc6W57UJwpI9+L0hFJkizraVBA1Q==",
+      "license": "MIT",
+      "dependencies": {
+        "@posthog/types": "^1.416.0"
+      }
+    },
+    "node_modules/@posthog/types": {
+      "version": "1.416.0",
+      "resolved": "https://registry.npmjs.org/@posthog/types/-/types-1.416.0.tgz",
+      "integrity": "sha512-0/9+02s/0uDyrH4G/qUg1yyl6gXUg8Uuxw/PlDad3KLzo9FFS9zS/kAQaEshx/saVGupj1aAy/4EUBxWisBogw==",
+      "license": "MIT"
+    },
     "node_modules/@rollup/rollup-android-arm-eabi": {
       "version": "4.63.1",
       "resolved": "https://registry.npmjs.org/@rollup/rollup-android-arm-eabi/-/rollup-android-arm-eabi-4.63.1.tgz",
@@ -895,6 +922,36 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@types/trusted-types": {
+      "version": "2.0.7",
+      "resolved": "https://registry.npmjs.org/@types/trusted-types/-/trusted-types-2.0.7.tgz",
+      "integrity": "sha512-ScaPdn1dQczgbl0QFTeTOmVHFULt394XJgOQNoyVhZ6r2vLnMLJfBPd53SB52T/3G36VI1/g2MZaX0cwDuXsfw==",
+      "license": "MIT",
+      "optional": true
+    },
+    "node_modules/core-js": {
+      "version": "3.51.0",
+      "resolved": "https://registry.npmjs.org/core-js/-/core-js-3.51.0.tgz",
+      "integrity": "sha512-7bDKx/5jm5MxzsXxc93g6Z2+4ZsuT/MddrfRmTDJNAkWsYWHU8EVNEsBiIEWnMAMCHMmRfUEjkuo3jeNBOIHRw==",
+      "hasInstallScript": true,
+      "license": "MIT",
+      "engines": {
+        "node": "*"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/core-js"
+      }
+    },
+    "node_modules/dompurify": {
+      "version": "3.4.17",
+      "resolved": "https://registry.npmjs.org/dompurify/-/dompurify-3.4.17.tgz",
+      "integrity": "sha512-B/pSlYVHQ58kqISD/yDjuJ1yfzI34m1gF4lAod2bwSRhiN4K5Cl3H8Af7hqB2PmTL911tdEudnnXn5FnhRoz0w==",
+      "license": "(MPL-2.0 OR Apache-2.0)",
+      "optionalDependencies": {
+        "@types/trusted-types": "^2.0.7"
+      }
+    },
     "node_modules/esbuild": {
       "version": "0.25.12",
       "resolved": "https://registry.npmjs.org/esbuild/-/esbuild-0.25.12.tgz",
@@ -955,6 +1012,12 @@
         }
       }
     },
+    "node_modules/fflate": {
+      "version": "0.4.9",
+      "resolved": "https://registry.npmjs.org/fflate/-/fflate-0.4.9.tgz",
+      "integrity": "sha512-zdxgIEddhfsyCaWpJ2SdXEP8ZMrKJ6+5jl4OupODcywU0IhRk6gdXuVGcPICyfx2H97hVK7xmJtRLPjkxAX8Vw==",
+      "license": "MIT"
+    },
     "node_modules/fsevents": {
       "version": "2.3.3",
       "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.3.tgz",
@@ -1047,6 +1110,36 @@
         "node": "^10 || ^12 || >=14"
       }
     },
+    "node_modules/posthog-js": {
+      "version": "1.438.17",
+      "resolved": "https://registry.npmjs.org/posthog-js/-/posthog-js-1.438.17.tgz",
+      "integrity": "sha512-BM0VHG/DTppBUX9TjQ3aX/+xKsmrMgYTWyGrhxL2GV3oWGleyDLUymjGBZHWXlS7bIMHMMJloSWWXBmZQGp5NQ==",
+      "license": "(Apache-2.0 AND MIT)",
+      "dependencies": {
+        "@posthog/browser-common": "^0.9.8",
+        "@posthog/core": "^1.59.4",
+        "@posthog/types": "^1.416.0",
+        "core-js": "^3.49.0",
+        "dompurify": "^3.4.13",
+        "fflate": "^0.4.8",
+        "preact": "^10.29.3",
+        "query-selector-shadow-dom": "^1.0.1",
+        "web-vitals": "^6.2.1",
+        "web-vitals-soft-navs": "npm:web-vitals@6.2.1"
+      },
+      "peerDependencies": {
+        "@types/react": ">=16.8.0",
+        "react": ">=16.8.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/react": {
+          "optional": true
+        },
+        "react": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/preact": {
       "version": "10.29.8",
       "resolved": "https://registry.npmjs.org/preact/-/preact-10.29.8.tgz",
@@ -1065,6 +1158,12 @@
         }
       }
     },
+    "node_modules/query-selector-shadow-dom": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/query-selector-shadow-dom/-/query-selector-shadow-dom-1.0.1.tgz",
+      "integrity": "sha512-lT5yCqEBgfoMYpf3F2xQRK7zEr1rhIIZuceDK6+xRkJQ4NMbHTwXqk4NkwDwQMNqXgG9r9fyHnzwNVs6zV5KRw==",
+      "license": "MIT"
+    },
     "node_modules/react": {
       "version": "19.2.8",
       "resolved": "https://registry.npmjs.org/react/-/react-19.2.8.tgz",
@@ -1236,6 +1335,19 @@
           "optional": true
         }
       }
+    },
+    "node_modules/web-vitals": {
+      "version": "6.2.3",
+      "resolved": "https://registry.npmjs.org/web-vitals/-/web-vitals-6.2.3.tgz",
+      "integrity": "sha512-Dmy+vdO1UPMqXiAtZSNayhl4f794Bxfd94W4HIj2HlYtczEQfEOon969memlcpcHrTuOKLa5baFjX7WbgmOq+A==",
+      "license": "Apache-2.0"
+    },
+    "node_modules/web-vitals-soft-navs": {
+      "name": "web-vitals",
+      "version": "6.2.1",
+      "resolved": "https://registry.npmjs.org/web-vitals/-/web-vitals-6.2.1.tgz",
+      "integrity": "sha512-rLcLXA2sx6+9dE88NHFubwTtGxpK4yYBLj6qHPdFoCaLr0cXGb4efOqtKLlm4loGA4OEKHIQKMKzZkKyOh5ctw==",
+      "license": "Apache-2.0"
     }
   }
 }
diff --git a/package.json b/package.json
index e27cd7fd..52889f6e 100644
--- a/package.json
+++ b/package.json
@@ -16,6 +16,7 @@
     "@openmouse/keyboard-protocol": "1.1.0",
     "@openmouse/protocol": "0.45.2",
     "lucide-react": "^1.43.0",
+    "posthog-js": "^1.438.17",
     "preact": "^10.29.8"
   },
   "devDependencies": {
diff --git a/public/_headers b/public/_headers
index 31ef68a7..cf01f37a 100644
--- a/public/_headers
+++ b/public/_headers
@@ -22,7 +22,7 @@
 # isolation buys the app nothing it needs.
 
 /*
-  Content-Security-Policy: default-src 'self'; script-src 'self'; script-src-attr 'none'; style-src 'self' https://fonts.googleapis.com; style-src-attr 'none'; font-src 'self' data: https://fonts.gstatic.com; img-src 'self' data: blob: https://img.openmouse.app https://cdn.cloudflare.steamstatic.com https://shared.akamai.steamstatic.com https://store-images.s-microsoft.com http://127.0.0.1:17846; media-src 'self'; connect-src 'self' https://api.github.com https://cdn.jsdelivr.net http://127.0.0.1:17846 ws://127.0.0.1:17846; worker-src 'self'; manifest-src 'self'; object-src 'none'; base-uri 'none'; form-action 'self'; frame-ancestors 'none'; require-trusted-types-for 'script'; trusted-types openmouse
+  Content-Security-Policy: default-src 'self'; script-src 'self' https://us-assets.i.posthog.com; script-src-attr 'none'; style-src 'self' https://fonts.googleapis.com; style-src-attr 'none'; font-src 'self' data: https://fonts.gstatic.com; img-src 'self' data: blob: https://img.openmouse.app https://cdn.cloudflare.steamstatic.com https://shared.akamai.steamstatic.com https://store-images.s-microsoft.com http://127.0.0.1:17846; media-src 'self'; connect-src 'self' https://us.i.posthog.com https://us-assets.i.posthog.com https://api.github.com https://cdn.jsdelivr.net http://127.0.0.1:17846 ws://127.0.0.1:17846; worker-src 'self'; manifest-src 'self'; object-src 'none'; base-uri 'none'; form-action 'self'; frame-ancestors 'none'; require-trusted-types-for 'script'; trusted-types openmouse
   X-Content-Type-Options: nosniff
   X-Frame-Options: DENY
   Referrer-Policy: strict-origin-when-cross-origin
diff --git a/src/device/controller.ts b/src/device/controller.ts
index 7ce0bbf8..4eaf8cfc 100644
--- a/src/device/controller.ts
+++ b/src/device/controller.ts
@@ -1,4 +1,5 @@
 import { emptyKeyboardWorkspace } from "./keyboard-workspace.ts";
+import { track, deviceProps, scrubError } from "../platform/analytics";
 import type { KeyboardCommand } from "./keyboard-workspace.ts";
 import { cachedBatterySamples, estimateBatteryTime, estimateFromRatedLife, ratedBattery, recordBatterySample, type BatteryMode } from "../features/devices/battery-history";
 import { bridgeEmptyResultMessage, isBridgeHidActive } from "../features/bridge/bridge-hid";
@@ -2244,6 +2245,7 @@ export async function flashPendingChanges(): Promise<void> {
     : st("ctl.flashedMany", { n: written });
   setReadStatus(flashed);
   pushToast("success", flashed);
+  track("pending_changes_applied", { change_count: written });
 }
 
 function endDeviceWrite(): void {
@@ -2366,7 +2368,15 @@ function recordDiagnosticCommand(command: string): void {
   renderDeviceDiagnostics(latestDiagnosticStatus);
 }
 
-function recordDiagnosticError(error: unknown, fallback: string): void {
+/** Model-level facts about the active device for analytics: no serials or ids. */
+function activeDeviceFacts(): { vendorId: number; productId: number; productName: string } | undefined {
+  return activeDevice
+    ? { vendorId: activeDevice.vendorId, productId: activeDevice.productId, productName: activeDevice.productName }
+    : undefined;
+}
+
+function recordDiagnosticError(error: unknown, fallback: string, report = true): void {
+  if (report) track("device_error", { ...deviceProps(activeDeviceFacts()), ...scrubError(error) });
   lastDiagnosticError = diagnosticErrorMessage(error, fallback);
   markHidActivity(lastDiagnosticError, { failed: true });
   renderDeviceDiagnostics(latestDiagnosticStatus);
@@ -2619,6 +2629,7 @@ export function downloadDiagnostics(): void {
   link.click();
   URL.revokeObjectURL(url);
   diagnosticDownloadStatus = st("ctl.savedName", { name });
+  track("diagnostics_downloaded");
   emit();
 }
 
@@ -3651,7 +3662,9 @@ function handleHidDisconnect(event: HIDConnectionEvent): void {
 }
 
 /** Ask the browser for a device, then pick the best keyboard or mouse client. */
-async function requestSupportedClient(): Promise<SupportedClient | KeyboardClient | null> {
+async function requestSupportedClient(
+  onSelected?: (device: HIDDevice) => void,
+): Promise<SupportedClient | KeyboardClient | null> {
   if (!navigator.hid) throw new Error(st("ctl.noWebHid"));
   const devices = await navigator.hid.requestDevice({ filters: HID_FILTERS });
   if (devices.length === 0) {
@@ -3667,6 +3680,9 @@ async function requestSupportedClient(): Promise<SupportedClient | KeyboardClien
     }
     return null;
   }
+  // Remember what was picked now, so a failure reports this device and not
+  // whichever one happens to be active when the error lands.
+  onSelected?.(devices[0]);
 
   if (devices.some((device) => eggWeIsSupported(device))) {
     const weClient = eggWeFromAuthorized(await eggWeAuthorizedPool(devices));
@@ -3764,8 +3780,11 @@ export async function connect(): Promise<void> {
   readStatus = st("ctl.choosePrompt");
   emit();
 
+  let attempted: { vendorId: number; productId: number; productName: string } | undefined;
   try {
-    const client = await requestSupportedClient();
+    const client = await requestSupportedClient((device) => {
+      attempted = { vendorId: device.vendorId, productId: device.productId, productName: device.productName };
+    });
     if (!client) {
       deviceStatusText = st("ctl.notConnected");
       readStatus = st("ctl.noSelection");
@@ -3779,10 +3798,15 @@ export async function connect(): Promise<void> {
     });
     emit();
     await activateClient(client);
+    track("device_connected", deviceProps(attempted));
   } catch (error) {
     const message = error instanceof Error ? error.message : "Unable to read the mouse.";
     const wrongDevice = error instanceof NotAMouseError;
-    if (!wrongDevice) recordDiagnosticError(error, message);
+    if (!wrongDevice) recordDiagnosticError(error, message, false);
+    track(wrongDevice ? "device_not_a_mouse" : "device_connection_failed", {
+      ...deviceProps(attempted),
+      ...scrubError(error),
+    });
     if (eggClient() ?? eggWeClient()) {
       await active?.close().catch(() => undefined);
       active = null;
diff --git a/src/features/games/GameRequestDialog.tsx b/src/features/games/GameRequestDialog.tsx
index c93862df..ee8cc61b 100644
--- a/src/features/games/GameRequestDialog.tsx
+++ b/src/features/games/GameRequestDialog.tsx
@@ -1,4 +1,5 @@
 import { displayText } from "../../i18n/index";
+import { track } from "../../platform/analytics";
 import { useUiLocale } from "../../shared/ui-locale";
 import { useEffect, useRef, useState, type ReactNode } from "react";
 import { Check, Copy, Gamepad2 } from "lucide-react";
@@ -215,6 +216,7 @@ export function GameRequestDialog({ open, onClose, locale = "en", bridgeActive,
         /* the cooldown is a courtesy; storage failures just skip it */
       }
       control.pushToast("success", t(locale, "gamereq.sent"), tp(locale, "gamereq.sentDetail", { name: trimmedName }));
+      track("game_request_submitted", { request_kind: kind });
       setName("");
       setPath("");
       onClose();
diff --git a/src/features/hardware-test/HardwareTestPage.tsx b/src/features/hardware-test/HardwareTestPage.tsx
index 53bab7f6..e249a2a0 100644
--- a/src/features/hardware-test/HardwareTestPage.tsx
+++ b/src/features/hardware-test/HardwareTestPage.tsx
@@ -1,4 +1,5 @@
 import { displayText } from "../../i18n/index";
+import { track } from "../../platform/analytics";
 import { useCallback, useEffect, useRef, useState, type ReactNode } from "react";
 import * as control from "../../device/controller";
 import type { ControlSnapshot } from "../../device/types";
@@ -106,6 +107,7 @@ export function HardwareTestPage({ snapshot }: { snapshot: ControlSnapshot }): R
     setStages([]);
     setLiveSample(null);
     setSamplingElapsedMs(0);
+    track("hardware_test_started");
 
     void (async () => {
       let info = deviceInfoFromSnapshot(snapshot);
@@ -372,6 +374,7 @@ export function HardwareTestPage({ snapshot }: { snapshot: ControlSnapshot }): R
         build: snapshot.buildLabel,
         supportedPage: crosscheckSupportedDevices(info, verdict),
       });
+      track("hardware_test_completed", { verdict });
     })().catch(() => {
       addStage({ kind: "check", label: "The suite crashed — restart the test", state: "fail" });
       setReport(null);
@@ -393,6 +396,7 @@ export function HardwareTestPage({ snapshot }: { snapshot: ControlSnapshot }): R
     anchor.click();
     anchor.remove();
     URL.revokeObjectURL(url);
+    track("hardware_test_report_downloaded");
   }, [report, running]);
 
   // Opens the WebHID/Bridge device picker and connects the chosen mouse.
diff --git a/src/features/settings/InterfaceSettings.tsx b/src/features/settings/InterfaceSettings.tsx
index 6c0b1f40..522be54c 100644
--- a/src/features/settings/InterfaceSettings.tsx
+++ b/src/features/settings/InterfaceSettings.tsx
@@ -1,4 +1,5 @@
 import { displayText } from "../../i18n/index";
+import { analyticsAvailable, analyticsEnabled, setAnalyticsEnabled, track } from "../../platform/analytics";
 import { Globe, RotateCcw } from "lucide-react";
 import { useState, type ReactNode } from "react";
 import * as control from "../../device/controller";
@@ -48,6 +49,7 @@ export function ProfileKeyFields({ snapshot }: { snapshot: ControlSnapshot }): R
           onClick={() => {
             if (!key) return;
             void navigator.clipboard.writeText(key).then(() => {
+              track("profile_key_copied");
               setCopied(true);
               setTimeout(() => setCopied(false), 1500);
             });
@@ -116,6 +118,7 @@ function SettingsGroup({ id, title, children }: { id: string; title: string; chi
 export function InterfaceSettings({ snapshot }: { snapshot: ControlSnapshot }): ReactNode {
   const preferences = snapshot.preferences;
   const locale = preferences.locale;
+  const [analyticsOn, setAnalyticsOn] = useState(analyticsEnabled);
   const set = <K extends keyof typeof preferences>(key: K) => (value: (typeof preferences)[K]): void =>
     control.setPreference(key, value);
 
@@ -192,6 +195,12 @@ export function InterfaceSettings({ snapshot }: { snapshot: ControlSnapshot }):
         {toggle("interface-sounds", t(locale, "set.soundTitle"), t(locale, "set.soundDescription"), preferences.enabledSounds, set("enabledSounds"))}
         {toggle("interface-expand-sections", t(locale, "set.advancedEditors"), t(locale, "set.advancedEditorsBody"), preferences.expandSections, set("expandSections"))}
         {toggle("interface-show-experimental", t(locale, "set.experimentalTitle"), t(locale, "set.experimentalBody"), preferences.showExperimental, set("showExperimental"))}
+        {analyticsAvailable
+          ? toggle("interface-analytics", t(locale, "set.analytics"), t(locale, "set.analyticsBody"), analyticsOn, (next) => {
+              setAnalyticsEnabled(next);
+              setAnalyticsOn(next);
+            })
+          : null}
       </SettingsGroup>
 
       <SettingsGroup id="settings-profile-key" title={t(locale, "set.profileKey")}>
diff --git a/src/i18n/index.ts b/src/i18n/index.ts
index 4cde08fc..8664ca9a 100644
--- a/src/i18n/index.ts
+++ b/src/i18n/index.ts
@@ -251,6 +251,8 @@ const en = {
   "set.writes": "WRITES",
   "set.instantFlash": "Instant flash",
   "set.instantFlashBody": "Write each change to the mouse as soon as you make it, instead of staging it for the flash bar.",
+  "set.analytics": "Share anonymous diagnostics",
+  "set.analyticsBody": "Send anonymous usage and device error reports so supported devices can be fixed faster. No IP address, serial number or personal data is sent.",
   "set.flashImmediately": "Flash immediately",
   "set.sections": "SECTIONS",
   "set.advancedEditors": "Advanced editors",
diff --git a/src/i18n/locales/ar.ts b/src/i18n/locales/ar.ts
index c760d046..04abbb35 100644
--- a/src/i18n/locales/ar.ts
+++ b/src/i18n/locales/ar.ts
@@ -193,6 +193,8 @@ export const ar: Record<I18nKey, string> = {
   "set.writes": "الكتابة",
   "set.instantFlash": "التثبيت الفوري",
   "set.instantFlashBody": "اكتب كل تغيير إلى الماوس فور إجرائه، بدلًا من تجهيزه لشريط التثبيت.",
+  "set.analytics": "مشاركة بيانات التشخيص المجهولة",
+  "set.analyticsBody": "إرسال تقارير مجهولة عن الاستخدام وأخطاء الأجهزة لإصلاح الأجهزة المدعومة بشكل أسرع. لا يتم إرسال عنوان IP أو الرقم التسلسلي أو أي بيانات شخصية.",
   "set.flashImmediately": "ثبّت فورًا",
   "set.sections": "الأقسام",
   "set.advancedEditors": "المحررات المتقدمة",
diff --git a/src/i18n/locales/de.ts b/src/i18n/locales/de.ts
index eb5b34dc..9a6d5839 100644
--- a/src/i18n/locales/de.ts
+++ b/src/i18n/locales/de.ts
@@ -194,6 +194,8 @@ export const de: Record<I18nKey, string> = {
   "set.writes": "SCHREIBVORGÄNGE",
   "set.instantFlash": "Sofortiges Flashen",
   "set.instantFlashBody": "Schreibt jede Änderung sofort auf die Maus, statt sie für die Flash-Leiste vorzubereiten.",
+  "set.analytics": "Anonyme Diagnosedaten teilen",
+  "set.analyticsBody": "Anonyme Nutzungs- und Gerätefehlerberichte senden, damit unterstützte Geräte schneller verbessert werden. Es werden weder IP-Adresse noch Seriennummer oder persönliche Daten gesendet.",
   "set.flashImmediately": "Sofort flashen",
   "set.sections": "ABSCHNITTE",
   "set.advancedEditors": "Erweiterte Editoren",
diff --git a/src/i18n/locales/es.ts b/src/i18n/locales/es.ts
index d4e9e8b1..71d25e6f 100644
--- a/src/i18n/locales/es.ts
+++ b/src/i18n/locales/es.ts
@@ -194,6 +194,8 @@ export const es: Record<I18nKey, string> = {
   "set.writes": "ESCRITURAS",
   "set.instantFlash": "Grabado instantáneo",
   "set.instantFlashBody": "Escribe cada cambio en el mouse en cuanto lo haces, en lugar de prepararlo en la barra de grabado.",
+  "set.analytics": "Compartir diagnósticos anónimos",
+  "set.analyticsBody": "Envía informes anónimos de uso y errores de dispositivos para corregir antes los dispositivos compatibles. No se envía la dirección IP, el número de serie ni datos personales.",
   "set.flashImmediately": "Grabar inmediatamente",
   "set.sections": "SECCIONES",
   "set.advancedEditors": "Editores avanzados",
diff --git a/src/i18n/locales/fr.ts b/src/i18n/locales/fr.ts
index b27d3941..826a0c2b 100644
--- a/src/i18n/locales/fr.ts
+++ b/src/i18n/locales/fr.ts
@@ -194,6 +194,8 @@ export const fr: Record<I18nKey, string> = {
   "set.writes": "ÉCRITURES",
   "set.instantFlash": "Gravure instantanée",
   "set.instantFlashBody": "Écrit chaque modification sur la souris dès que vous la faites, au lieu de la préparer pour la barre de gravure.",
+  "set.analytics": "Partager des diagnostics anonymes",
+  "set.analyticsBody": "Envoie des rapports anonymes d'utilisation et d'erreurs d'appareil pour corriger plus vite les appareils pris en charge. Aucune adresse IP, aucun numéro de série ni donnée personnelle n'est envoyé.",
   "set.flashImmediately": "Graver immédiatement",
   "set.sections": "SECTIONS",
   "set.advancedEditors": "Éditeurs avancés",
diff --git a/src/i18n/locales/ja.ts b/src/i18n/locales/ja.ts
index 7dfc9922..75bf05ca 100644
--- a/src/i18n/locales/ja.ts
+++ b/src/i18n/locales/ja.ts
@@ -194,6 +194,8 @@ export const ja: Record<I18nKey, string> = {
   "set.writes": "書き込み",
   "set.instantFlash": "即時書き込み",
   "set.instantFlashBody": "変更を書き込みバーに保留せず、変更するたびにすぐマウスへ書き込みます。",
+  "set.analytics": "匿名の診断情報を共有",
+  "set.analyticsBody": "対応デバイスをより早く改善するため、匿名の利用状況とデバイスエラーのレポートを送信します。IPアドレス、シリアル番号、個人情報は送信されません。",
   "set.flashImmediately": "即座に書き込む",
   "set.sections": "セクション",
   "set.advancedEditors": "詳細エディター",
diff --git a/src/i18n/locales/ko.ts b/src/i18n/locales/ko.ts
index 73534909..a7c114b5 100644
--- a/src/i18n/locales/ko.ts
+++ b/src/i18n/locales/ko.ts
@@ -194,6 +194,8 @@ export const ko: Record<I18nKey, string> = {
   "set.writes": "쓰기",
   "set.instantFlash": "즉시 기록",
   "set.instantFlashBody": "변경 사항을 기록 대기열에 두지 않고, 변경할 때마다 바로 마우스에 기록합니다.",
+  "set.analytics": "익명 진단 정보 공유",
+  "set.analyticsBody": "지원 기기를 더 빨리 개선할 수 있도록 익명의 사용 및 기기 오류 보고서를 보냅니다. IP 주소, 일련번호, 개인 정보는 전송되지 않습니다.",
   "set.flashImmediately": "즉시 기록",
   "set.sections": "섹션",
   "set.advancedEditors": "고급 편집기",
diff --git a/src/i18n/locales/pt.ts b/src/i18n/locales/pt.ts
index 6e67ec20..74442585 100644
--- a/src/i18n/locales/pt.ts
+++ b/src/i18n/locales/pt.ts
@@ -194,6 +194,8 @@ export const pt: Record<I18nKey, string> = {
   "set.writes": "GRAVAÇÃO",
   "set.instantFlash": "Gravação instantânea",
   "set.instantFlashBody": "Grava cada mudança no mouse assim que você a faz, em vez de acumular para a barra de aplicação.",
+  "set.analytics": "Partilhar diagnósticos anónimos",
+  "set.analyticsBody": "Envia relatórios anónimos de utilização e de erros de dispositivos para corrigir mais depressa os dispositivos suportados. Não é enviado endereço IP, número de série nem dados pessoais.",
   "set.flashImmediately": "Gravar na hora",
   "set.sections": "SEÇÕES",
   "set.advancedEditors": "Editores avançados",
diff --git a/src/i18n/locales/ru.ts b/src/i18n/locales/ru.ts
index e3e6c766..45c26415 100644
--- a/src/i18n/locales/ru.ts
+++ b/src/i18n/locales/ru.ts
@@ -193,6 +193,8 @@ export const ru: Record<I18nKey, string> = {
   "set.writes": "ЗАПИСЬ",
   "set.instantFlash": "Мгновенная прошивка",
   "set.instantFlashBody": "Записывать каждое изменение в мышь сразу, не откладывая его в панель прошивки.",
+  "set.analytics": "Делиться анонимной диагностикой",
+  "set.analyticsBody": "Отправлять анонимные отчёты об использовании и ошибках устройств, чтобы быстрее улучшать поддержку устройств. IP-адрес, серийный номер и личные данные не передаются.",
   "set.flashImmediately": "Прошивать сразу",
   "set.sections": "РАЗДЕЛЫ",
   "set.advancedEditors": "Расширенные редакторы",
diff --git a/src/i18n/locales/tr.ts b/src/i18n/locales/tr.ts
index ab6504dc..f77c6ec5 100644
--- a/src/i18n/locales/tr.ts
+++ b/src/i18n/locales/tr.ts
@@ -182,6 +182,8 @@ export const tr: Record<I18nKey, string> = {
   "set.writes": "CİHAZA YAZMA",
   "set.instantFlash": "Anında yazma",
   "set.instantFlashBody": "Değişiklikleri yazma çubuğunda bekletmek yerine, yaptığınız anda fareye yazın.",
+  "set.analytics": "Anonim tanılama verilerini paylaş",
+  "set.analyticsBody": "Desteklenen cihazları daha hızlı iyileştirmek için anonim kullanım ve cihaz hatası raporları gönderir. IP adresi, seri numarası veya kişisel veri gönderilmez.",
   "set.flashImmediately": "Hemen cihaza yaz",
   "set.sections": "BÖLÜMLER",
   "set.advancedEditors": "Gelişmiş düzenleyiciler",
diff --git a/src/i18n/locales/vi.ts b/src/i18n/locales/vi.ts
index 2e0d7f36..d5e89d0a 100644
--- a/src/i18n/locales/vi.ts
+++ b/src/i18n/locales/vi.ts
@@ -146,6 +146,8 @@ export const vi: Record<I18nKey, string> = {
   "set.writes": "GHI",
   "set.instantFlash": "Ghi tức thì",
   "set.instantFlashBody": "Ghi từng thay đổi vào chuột ngay khi bạn thực hiện, thay vì đưa vào hàng chờ trên thanh ghi.",
+  "set.analytics": "Chia sẻ chẩn đoán ẩn danh",
+  "set.analyticsBody": "Gửi báo cáo ẩn danh về mức sử dụng và lỗi thiết bị để cải thiện thiết bị được hỗ trợ nhanh hơn. Không gửi địa chỉ IP, số sê-ri hay dữ liệu cá nhân.",
   "set.flashImmediately": "Ghi ngay",
   "set.sections": "CÁC MỤC",
   "set.advancedEditors": "Trình chỉnh sửa nâng cao",
diff --git a/src/i18n/locales/zh.ts b/src/i18n/locales/zh.ts
index 61e4dc26..925c43fc 100644
--- a/src/i18n/locales/zh.ts
+++ b/src/i18n/locales/zh.ts
@@ -194,6 +194,8 @@ export const zh: Record<I18nKey, string> = {
   "set.writes": "写入",
   "set.instantFlash": "即时写入",
   "set.instantFlashBody": "每次修改后立即写入鼠标，而不是先暂存到写入栏。",
+  "set.analytics": "共享匿名诊断信息",
+  "set.analyticsBody": "发送匿名的使用情况和设备错误报告,以便更快改进受支持的设备。不会发送 IP 地址、序列号或个人数据。",
   "set.flashImmediately": "立即写入",
   "set.sections": "分区",
   "set.advancedEditors": "高级编辑器",
diff --git a/src/main.tsx b/src/main.tsx
index d5fb298a..e2b84071 100644
--- a/src/main.tsx
+++ b/src/main.tsx
@@ -1,5 +1,6 @@
 import type { ReactNode } from "react";
 import { createRoot } from "react-dom/client";
+import "./platform/analytics";
 import "./styles/index.css";
 import { App } from "./app/App";
 import { UnsupportedNotice } from "./app/UnsupportedNotice";
diff --git a/src/platform/analytics.ts b/src/platform/analytics.ts
new file mode 100644
index 00000000..4316b54a
--- /dev/null
+++ b/src/platform/analytics.ts
@@ -0,0 +1,109 @@
+import posthogClient from "posthog-js";
+
+const posthogKey = import.meta.env.VITE_POSTHOG_KEY;
+const posthogHost = import.meta.env.VITE_POSTHOG_HOST;
+
+// Without both variables (local dev, forks, previews) analytics is a no-op.
+export const posthog = posthogKey && posthogHost ? posthogClient : undefined;
+
+if (posthog) {
+  posthog.init(posthogKey!, {
+    api_host: posthogHost!,
+    defaults: "2026-05-30",
+    // Anonymous random id in localStorage only: counts users and return visits.
+    persistence: "localStorage",
+    ip: false,
+    respect_dnt: true,
+    autocapture: false,
+    disable_session_recording: true,
+    person_profiles: "identified_only",
+    capture_exceptions: true,
+    before_send: scrubExceptionEvent,
+  });
+}
+
+/** Whether anonymous diagnostics are being sent (on unless the user opted out). */
+export function analyticsEnabled(): boolean {
+  return posthog ? !posthog.has_opted_out_capturing() : false;
+}
+
+export function setAnalyticsEnabled(enabled: boolean): void {
+  if (!posthog) return;
+  if (enabled) posthog.opt_in_capturing();
+  else posthog.opt_out_capturing();
+}
+
+/** Whether this build reports anything, so Settings can hide a dead switch. */
+export const analyticsAvailable = posthog !== undefined;
+
+/** Model-level device facts only: never serials, receiver ids or user text. */
+export interface DeviceFacts {
+  vendorId?: number;
+  productId?: number;
+  productName?: string;
+  brand?: string;
+}
+
+export function deviceProps(device: DeviceFacts | null | undefined): Record<string, string | number> {
+  const props: Record<string, string | number> = {};
+  if (!device) return props;
+  if (device.vendorId !== undefined) props.vendor_id = device.vendorId;
+  if (device.productId !== undefined) props.product_id = device.productId;
+  if (device.productName) props.product_name = device.productName.slice(0, 80);
+  if (device.brand) props.brand = device.brand.slice(0, 40);
+  return props;
+}
+
+/** Text with emails, paths and long hex ids (serials, receiver ids) removed, and capped. */
+function scrubText(raw: string): string {
+  return raw
+    .replace(/[\w.+-]+@[\w-]+\.[\w.]+/g, "<email>")
+    .replace(/(?:[A-Za-z]:)?[\\/][\w .\\/-]{3,}/g, "<path>")
+    .replace(/\b[0-9a-fA-F]{12,}\b/g, "<id>")
+    .slice(0, 200);
+}
+
+export function scrubError(error: unknown): { error_name: string; error_message: string } {
+  const name = error instanceof Error ? error.name : "Error";
+  return { error_name: name, error_message: scrubText(error instanceof Error ? error.message : String(error)) };
+}
+
+interface ExceptionFrame { filename?: string; abs_path?: string; [key: string]: unknown }
+interface ExceptionEntry { type?: string; value?: string; stacktrace?: { frames?: ExceptionFrame[] }; [key: string]: unknown }
+interface OutgoingEvent { event: string; properties?: Record<string, unknown> }
+
+/** Frame files stay only when they are the app's own bundles, so stacks still de-minify. */
+function ownFile(file: string | undefined): string | undefined {
+  return file && file.startsWith(location.origin) ? file.split(/[?#]/)[0] : undefined;
+}
+
+/** Scrubs automatic `$exception` events before they leave the browser. */
+function scrubExceptionEvent<T extends OutgoingEvent | null>(event: T): T {
+  if (!event || event.event !== "$exception" || !event.properties) return event;
+  const props = event.properties;
+  const list = props.$exception_list;
+  if (Array.isArray(list)) {
+    props.$exception_list = (list as ExceptionEntry[]).map((entry) => ({
+      ...entry,
+      value: typeof entry.value === "string" ? scrubText(entry.value) : entry.value,
+      stacktrace: entry.stacktrace
+        ? {
+            ...entry.stacktrace,
+            frames: entry.stacktrace.frames?.map((frame) => ({
+              ...frame,
+              filename: ownFile(frame.filename),
+              abs_path: ownFile(frame.abs_path),
+            })),
+          }
+        : entry.stacktrace,
+    }));
+  }
+  for (const key of ["$exception_message", "$exception_value"]) {
+    if (typeof props[key] === "string") props[key] = scrubText(props[key] as string);
+  }
+  return event;
+}
+
+export function track(event: string, props?: Record<string, unknown>): void {
+  posthog?.capture(event, props);
+}
diff --git a/test/security-headers.test.ts b/test/security-headers.test.ts
index f0eb4eab..5fe482ae 100644
--- a/test/security-headers.test.ts
+++ b/test/security-headers.test.ts
@@ -42,7 +42,7 @@ test("public/_headers mirrors the canonical security header set", () => {
 
 test("the deployed CSP keeps scripts same-origin and inline-free", () => {
   assert.equal(directive("default-src"), "default-src 'self'");
-  assert.equal(directive("script-src"), "script-src 'self'");
+  assert.equal(directive("script-src"), "script-src 'self' https://us-assets.i.posthog.com");
   assert.ok(!CSP.includes("'unsafe-inline'"), "no directive may allow inline code");
   assert.ok(!CSP.includes("'unsafe-eval'"), "eval must stay blocked");
   assert.equal(directive("script-src-attr"), "script-src-attr 'none'");
@@ -61,6 +61,8 @@ test("the deployed CSP enforces Trusted Types with the app policy", () => {
 test("the deployed CSP allows every origin the app talks to", () => {
   const connect = directive("connect-src");
   for (const origin of [
+    "https://us.i.posthog.com",
+    "https://us-assets.i.posthog.com",
     "https://api.github.com",
     "https://cdn.jsdelivr.net",
     "http://127.0.0.1:17846",
@@ -68,6 +70,7 @@ test("the deployed CSP allows every origin the app talks to", () => {
   ]) {
     assert.ok(connect.includes(origin), `connect-src must include ${origin}`);
   }
+  assert.equal(directive("worker-src"), "worker-src 'self'");
   assert.ok(directive("style-src").includes("https://fonts.googleapis.com"));
   assert.ok(directive("font-src").includes("https://fonts.gstatic.com"));
   assert.ok(directive("img-src").includes("https://img.openmouse.app"));