v138 · network / connectivity

Cache sharing for extremely-pervasive resources

For a small number (hundreds) of hand-curated static third-party script, stylesheet and compression-dictionary resources that are used on a large portion of the web, Chrome will use a single-keyed HTTP cache to store those resources.

concepts

  1. Shared cache simulator

    Visit four imaginary sites, watch the byte counter. Toggle between pre-138 partitioned and 138+ pervasive-shared modes to feel the cross-origin re-download cost disappear.

  2. Eligibility checker

    Paste any URL. The page runs through Chrome’s allowlist + integrity criteria and explains exactly why a given resource is or isn’t a shared-cache candidate — the privacy fence.

  3. Allowlist explorer

    Five-gate checklist with 10 preset URLs (some pass, some fail). Plus a back-of-envelope savings estimator showing the bytes saved if a resource is shared.

  4. Pervasive resource tester

    Fetch popular CDN resources twice and measure timing differences between first and second load. Simulate cross-site navigation to see how Chrome 138's single-keyed pervasive cache avoids re-downloading across origins. Eligibility criteria inspector with preset URLs.

why it shipped

Partitioning the HTTP cache solved the privacy concerns with shared resources but incurred a performance (and potentially revenue) impact on the web.

references