## TL;DR

Upgrade the Firebase JS SDK to 11.1.0 or later. That release fixed the service-worker subscription race for the reporters in the thread.

## The error

```text
Failed to execute 'subscribe' on 'PushManager': Subscription failed - no active Service Worker
```

Intermittent when calling `getToken` from Firebase Cloud Messaging.

## Fix it

1. Check your Firebase JS SDK version:
   ```bash
   npm ls firebase
   ```
   Success check: the version is below 11.1.0, confirming you are affected.

2. Upgrade to 11.1.0 or later:
   ```bash
   npm install firebase@^11.1.0
   ```
   Success check: `npm ls firebase` shows 11.1.0+.

3. Retry `getToken`.
   Success check: the token resolves with no PushManager error.

## When this applies

- Firebase JS SDK below 11.1.0, `getToken` intermittently throws the PushManager error.
- Next.js (pages or app router) or any setup where the service worker registration races the token call.

## When it does not apply

- Permission denied; the user blocked notifications (different error).
- VAPID key misconfiguration.
- The service worker file itself fails to register (check the SW scope and file path).

## Compatibility

- firebase JS SDK 11.1.0+ (fixed). Affects all browsers; reported on macOS with Next.js 13.

## Variant phrasings

- Failed to execute subscribe on PushManager no active Service Worker
- firebase getToken PushManager subscription failed
- FCM getToken no active service worker

## Why it happens

`getToken` called `pushManager.subscribe` before the messaging service worker was active, a race in older SDK versions. 11.1.0 waits for the worker to be ready before subscribing.

## Edge cases

- If it persists on 11.1.0+, ensure only one messaging service worker is registered and the SW file is served from the app root.
- Source: https://github.com/firebase/firebase-js-sdk/issues/7575

---

## Vectle citations

- Exact version: <https://vectle.com/skills/skl_Ht0oIR_aAvDBfs-JmsEYkA/versions/skv_YH0qRTBAwDdgL9OLK1EkRQ>
- Canonical HTML skill page: <https://vectle.com/skills/skl_Ht0oIR_aAvDBfs-JmsEYkA>
- Current Markdown URL: <https://vectle.com/skills/skl_Ht0oIR_aAvDBfs-JmsEYkA/markdown>

## Selected public attribution and original notices/references

```json
{
  "author": "issueatlas",
  "client": null,
  "notices_and_references": [
    "https://github.com/firebase/firebase-js-sdk/issues/7575"
  ]
}
```