Published on Updated on

Review the API reference for workbox-core.

Workbox has been built to be modular, allowing developers to select the pieces they want to use without forcing them to download everything in a single file.

There is however overlap between modules, for example, each module will like need to interact with the console, throw meaningful errors and make use of the network or cache. To avoid each module implementing the same logic, workbox-core contains this common code which each module relies on.

This module does provide some functionality to developers, but beyond log levels and caching, workbox-core offers internal logic to each module, rather than the end developer.

View and Change the Default Cache Names

Workbox defines it's caches via cacheNames:

import {cacheNames} from 'workbox-core';


These cache names are constructed in the format of a prefix, a name and suffix, where the name changes based on the use of the cache.


You can change these default names by altering all or some of the values passed to setCacheNameDetails().

import {cacheNames, setCacheNameDetails} from 'workbox-core';

prefix: 'my-app',
suffix: 'v1',
precache: 'install-time',
runtime: 'run-time',
googleAnalytics: 'ga',

// Will print 'my-app-install-time-v1'

// Will print 'my-app-run-time-v1'

// Will print 'my-app-ga-v1'

The main use case for the prefix and suffix is that if you use Workbox for multiple projects and use the same localhost port for each project, setting a custom prefix for each module will prevent the caches from conflicting with each other.

Clients Claim

Some developers want to be able to publish a new service worker and have it control already-open web pages as soon as soon as it activates, which will not happen by default.

If you find yourself wanting this behavior, workbox-core provides a helper method:

import {clientsClaim} from 'workbox-core';

// This clientsClaim() should be at the top level
// of your service worker, not inside of, e.g.,
// an event handler.

The clientsClaim() method in workbox-core automatically adds an activate event listener to your service worker, and inside of it, calls self.clients.claim(). Calling self.clients.claim() before the current service worker activates will lead to a runtime exception, and workbox-core's wrapper helps ensure that you call it at the right time.

The skipWaiting wrapper is deprecated

Previous to Workbox v6, developers were also encouraged to use the skipWaiting() method from workbox-core. However, this method offered little value beyond what developers would get if they called self.skipWaiting() explicitly.

Because the legacy workbox-core wrapper also registered an install event handler in which self.skipWaiting() was called, the wrapper would not behave as expected if it were called inside of another event handler, like message, after installation had already completed.

For these reasons, workbox-core's skipWaiting() is deprecated, and developers should switch to calling self.skipWaiting() directly. Unlike with self.clients.claim(), self.skipWaiting() will not throw an exception if called at the "wrong" time, so there is no need to wrap it in an event handler.

If your web app lazy-loads resources that are uniquely versioned with, e.g., hashes in their URLs, it's recommended that you avoid using skip waiting. Enabling it could lead to failures when lazily-loading URLs that were previously precached and were purged during an updated service worker's activation.

Last updated: Improve article

We serve cookies on this site to analyze traffic, remember your preferences, and optimize your experience.