Layer0 Devtools is a widget that helps developers understand how their site interacts with Layer0, including:

  • Edge and browser caching
  • Prefetching
  • The flow of responses from serverless to the edge and browser caches

Live demo of Layer0 Devtools running on a React Storefront site


It’s likely that Devtools was added to your app when you ran 0 init. If that’s not the case, or your app predates Layer0 v2.22.0, follow these steps to add the Devtools to your app:


In order to enable Layer0 Devtools, first ensure that the @layer0/devtools and @layer0/prefetch packages have been added to your project. To install them using NPM, run:

npm i -D @layer0/devtools @layer0/prefetch

Or with Yarn

yarn add --dev @layer0/devtools @layer0/prefetch

Client Widget

Note: you can skip this step if you are using @layer0/next or @layer0/nuxt

Add the following to your client JavaScript bundle:

import installDevtools from '@layer0/devtools/install'


Alternatively, you can add the following script tag to your app’s HTML:

<script defer src="/__layer0__/devtools/install.js"></script>

Service Worker

Then, if you haven’t already, enable @layer0/prefetch in your service worker. See Prefetching for more information on enabling @layer0/prefetch.

Enabling or Disabling the Devtools

By default, Layer0 Devtools is enabled when your app is served from localhost, or any *.layer0-limelight.link domain.

To customize when Layer0 Devtools appear:

Per Environment

Using the Layer0 Developer Console, navigate to your environment and create an environment variable named PREVIEW_LAYER0_DEVTOOLS_ENABLED. Set the value to true or false to explicitly enable or disable the Devtools on the given environment.

Per Browsing Session

Point your browser to /__layer0__/devtools/enable or /__layer0__/devtools/disable to explicitly enable or disable Layer0 Devtools for your browsing session. This takes precedence over the environment config and the domain default.

If the Devtools were previously enabled and you disable them, you may want to remove the service worker to get rid of the Devtools-specific route handlers that were installed on-demand when enabling it. This can be done using the Application tab in Chrome Developer Tools.