Bundle diffing for EAS Update

Enable your project to accept bundle diffs when available.

Bundle diffing is in beta and may have limitations. See Current limitations for details.

Enable bundle diffing to let EAS Update deliver a bundle patch when possible. When you publish a new update, EAS Update can generate a smaller file containing only the differences between the bundle currently running on the device and the new bundle. This often reduces update download size significantly.

Prerequisites

Your app must use Expo SDK 55 or later.

Enable bundle diffing

In your project's app config, set updates.enableBsdiffPatchSupport to true:

{
  "expo": {
    "updates": {
      "enableBsdiffPatchSupport": true
    }
  }
}

Verify bundle diffs are being served

Expo website

You can confirm that bundle diffs are being served from the Update Details page. Open the Update Group you published, then select the platform you want to inspect.

Updates API

You can confirm that bundle diffs are being served by inspecting update logs with Updates.readLogEntriesAsync(). If your app received a patch, you will see an entry indicating it was successfully applied (for example, "patch successfully applied").

Patch generation and serving

EAS Update uses the bsdiff algorithm to generate bundle patches.

A patch is served only when:

• It's meaningfully smaller than the full bundle. If it isn't, EAS Update serves the full bundle instead.
• It can be computed efficiently. If generating the patch is too resource intensive, EAS Update serves the full bundle instead.

Current limitations

• Embedded bundles aren't eligible. The embedded bundle is never used as a base for patching. Devices must already be running a published update to receive a patch.
• Patches aren't guaranteed for every possible update pair immediately. When an update is published, EAS Update precomputes a patch only against the second-newest update on the channel. If a device requests the new update while running a different published update, it will initially receive the full bundle. A patch for that specific base update is then generated on demand and served to future similar requests.
• Patches are generated shortly after publishing. It can take a few minutes between publishing an update and the patch being ready. During that window, devices may receive the full bundle.