@sekmet/gatsby-plugin-offline

Adds drop-in support for making a Gatsby site work offline and more resistant to bad network connections. It creates a service worker for the site and loads the service worker into the client.

Plus adding push notification support and maybe to more service worker related events.

If you're using this plugin with gatsby-plugin-manifest (recommended) this plugin should be listed after that plugin so the manifest file can be included in the service worker.

Install

npm install --save @sekmet/gatsby-plugin-offline

How to use

// In your gatsby-config.js
plugins: [`@sekmet/gatsby-plugin-offline`]

Overriding options

When adding this plugin to your gatsby-config.js, you can pass in options (via the options key) to override the default Workbox config.

The default config is as follows. Warning: You can break the offline support by changing these options, so tread carefully.

const options = {
  importWorkboxFrom: `local`,
  globDirectory: rootDir,
  globPatterns,
  modifyUrlPrefix: {
    // If `pathPrefix` is configured by user, we should replace
    // the default prefix with `pathPrefix`.
    "/": `${pathPrefix}/`,
  },
  cacheId: `gatsby-plugin-offline`,
  // Don't cache-bust JS or CSS files, and anything in the static directory,
  // since these files have unique URLs and their contents will never change
  dontCacheBustUrlsMatching: /(\.js$|\.css$|static\/)/,
  runtimeCaching: [
    {
      // Use cacheFirst since these don't need to be revalidated (same RegExp
      // and same reason as above)
      urlPattern: /(\.js$|\.css$|static\/)/,
      handler: `cacheFirst`,
    },
    {
      // Add runtime caching of various other page resources
      urlPattern: /^https?:.*\.(png|jpg|jpeg|webp|svg|gif|tiff|js|woff|woff2|json|css)$/,
      handler: `staleWhileRevalidate`,
    },
    {
      // Google Fonts CSS (doesn't end in .css so we need to specify it)
      urlPattern: /^https?:\/\/fonts\.googleapis\.com\/css/,
      handler: `staleWhileRevalidate`,
    },
  ],
  skipWaiting: true,
  clientsClaim: true,
}

Remove

If you want to remove @sekmet/gatsby-plugin-offline from your site at a later point, substitute it with gatsby-plugin-remove-serviceworker to safely remove the service worker. First, install the new package:

npm install gatsby-plugin-remove-serviceworker
npm uninstall @sekmet/gatsby-plugin-offline

Then, update your gatsby-config.js:

 plugins: [
-  `@sekmet/gatsby-plugin-offline`,
+  `gatsby-plugin-remove-serviceworker`,
 ]

This will ensure that the worker is properly unregistered, instead of leaving an outdated version registered in users' browsers.

Notes

Empty View Source and SEO

Gatsby offers great SEO capabilities and that is no different with @sekmet/gatsby-plugin-offline. However, you shouldn't think that Gatsby doesn't serve HTML tags anymore when looking at your source code in the browser (with Right click => View source). View source doesn't represent the actual HTML data since gatsby-plugin-offline registers and loads a service worker that will cache and handle this differently. Your site is loaded from the service worker, not from its actual source (check your Network tab in the DevTools for that).

To see the HTML data that crawlers will receive, run this in your terminal:

curl https://www.yourdomain.tld

Alternatively you can have a look at the /public/index.html file in your project folder.

App shell and server logs

Server logs (like from Netlify analytics) may show a large number of pageviews to a route like /offline-plugin-app-shell-fallback/index.html, this is a result of @sekmet/gatsby-plugin-offline adding an app shell to the page. The app shell is a minimal amount of user interface that can be cached offline for reliable performance loading on repeat visits. The shell can be loaded from the cache, and the content of the site loaded into the shell by the service worker.