modern-spfFast same-origin navigation, the SPF way

Fetch only the fragments that change — never the whole page. A modern re-creation of YouTube's [SPF](https://github.com/youtube/spfjs), built on the Navigation API, view transitions, streaming, and ES modules.

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API reference

Fragment-only navigation

Clicking an spf-link fetches a small JSON response describing what changed — title, head, per-fragment body — and swaps it in via the Navigation API, instead of a full page load.

Streaming by default

Servers may answer with an NDJSON stream of parts so the page updates as the response arrives — head and body land before the stream finishes.

Hybrid response cache

An in-memory LRU plus the Cache API serve back/forward navigations instantly, while new navigations always hit the server unless a prefetched response is available.

Zero runtime dependencies

Evergreen browsers only, no polyfills. Built on modern primitives: Navigation API, constructable stylesheets, speculation rules, ES modules.

Concept-compatible with SPF

The familiar surface — spf.init, spf.navigate, spf* events, the spf-link class — with modern, Promise-aware, typed semantics.

Same-document view transitions

Default-on transitions around the DOM swap, respecting prefers-reduced-motion, with per-link and per-call opt-outs.