How Chrome 101’s Priority Hints and FedCM Can Boost Web Performance and Privacy

TL;TR

Chrome 101 officially launches Priority Hints (the fetchpriority attribute) to let developers specify resource loading priority, and begins Android trials of the Federated Credentials Management API (FedCM) to enable third‑party login without third‑party cookies.

Priority Hints

Priority Hints add the fetchpriority attribute to HTML elements (e.g., <img src="/images/test.png" fetchpriority="high"/>) and a priority option to the fetch API. The attribute accepts high, low, or auto (default). While browsers still consider many factors when ordering downloads, this hint gives developers a direct way to influence the order.

<!-- Through fetchpriority attribute specify image priority -->
<img src="/images/test.png" fetchpriority="high" />

<!-- Specify priority when using fetch -->
<script>
  fetch("https://example.com/", { priority: "low" }).then(data => {});
</script>

The hint is advisory, not decisive, to prevent abuse. In a Google Flight case, raising a background image’s priority reduced Largest Contentful Paint from 2.6 s to 1.9 s, demonstrating potential performance benefits.

Because the hint is a simple attribute, manually assigning priorities across a complex page can be cumbersome; automation via frameworks or tooling is preferable.

Federated Credentials Management API

FedCM aims to replace third‑party cookies for login flows. It introduces three roles:

Relying Party : the site that wants to let users log in with an external provider (e.g., Stack Overflow).

User Agent : the browser, which mediates between the Relying Party and the Identity Provider while protecting user privacy.

Identity Provider : the service that actually authenticates the user (e.g., Google, GitHub, Facebook).

FedCM lets the browser store login state instead of third‑party cookies. Chrome plans to roll it out on desktop in Chrome 102 and ship it in Chrome 105, but Safari and Firefox show little interest, so adoption may remain limited to Chrome and Google‑owned services.

Without third‑party cookies, many login flows will need to adapt, but the broader impact on advertising ecosystems is uncertain. While privacy improves, sites that rely on cookie‑based ad targeting may lose revenue.

Summary

Chrome 101’s new features are technically interesting but lack broad browser support. Priority Hints can improve perceived performance when used wisely, and FedCM offers a path toward cookie‑less authentication, though its future depends on cross‑browser adoption and ecosystem willingness to standardize login interfaces.

Overall, these changes illustrate how browser vendors balance performance, privacy, and standardization, often driven by regulatory pressure and competition.