fetchLater() quotas

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Deferred fetchLater() API fetches are batched and sent once the tab is closed. At this point, there is no way for the user to abort them. To avoid situations where documents abuse this bandwidth to send unlimited amounts of data over the network the API sets quotas on how much data can be deferred to be sent later.

These quotas can be managed through deferred-fetch and deferred-fetch-minimal Permissions Policy directives.

Overview

The overall quota for fetchLater() is 640KiB per document. By default, this is divided into a 512KiB top-level quota and a 128KiB shared quota:

  • The 512KiB top-level quota by default is for any fetchLater() requests made from the top-level document and direct subframes using that origin.
  • The 128KiB shared quota by default is for any fetchLater() requests made in cross-origin subframes (for example,

This would not be considered "same-origin", despite being hosted on the same origin as the top-level document, as the