Reference › Glossary

Glossary

Bare. An HTTP protocol where your server performs requests on the client's behalf. The destination goes in an X-Bare-URL header. TLS terminates on your server, so it can inspect target request and response data. It works on request/response serverless hosts. See Wisp vs Bare.

bare-mux. A library that puts one transport in a SharedWorker and lets every context (window, iframes, service worker) share it. Introduced in Ultraviolet 3.0 to make transports swappable. Deprecated as of 2.1.9 in favour of proxy-transports. See bare-mux and proxy-transports.

bare-as-module3. The bare-mux transport that speaks the Bare protocol. The only transport that works without WebSockets.

Chemical. A meta-framework wrapping Ultraviolet, Scramjet and Rammerhead behind one API. Fastest path if you do not care which engine you get; less useful if you want to understand the stack.

Codec. The function pair encoding a real URL into a proxied path and back. Ultraviolet defaults to xor; Scramjet's controller defaults to encodeURIComponent. Obfuscation, not encryption, the key is in the client bundle.

Controller. In Scramjet 2.x, the window-side object that owns the service worker connection, the transport, the cookie jar, and the frames. new Controller({ serviceworker, transport }).

COOP / COEP. Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy. Response headers required for cross-origin isolation, which is required for SharedArrayBuffer, which Scramjet's wasm rewriter needs. See Cross-origin isolation.

Cross-origin isolation. A browser state where a page has proven no untrusted cross-origin content shares its process. Grants access to SharedArrayBuffer. Check with crossOriginIsolated.

epoxy. A TLS and HTTP stack written in Rust, compiled to WebAssembly, speaking wisp. Lighter and faster than libcurl, slightly pickier on unusual servers. See Transports.

Frame. In Scramjet 2.x, one browsing context: an iframe plus its own URL prefix plus its plugins. controller.createFrame(element, { plugins }). Each frame is routed independently, which is what makes real tabs cheap.

Interception proxy. The current architecture: a service worker on your origin intercepts requests from proxied pages and rewrites the responses. Named in contrast to server-side rewriting proxies, which cannot see requests made by JavaScript at runtime.

libcurl. A build of curl compiled to WebAssembly, speaking wisp. The best-compatibility transport, and the heaviest.

Plugin. In Scramjet 2.x, a class extending ManagedPlugin whose install() taps a frame's hooks. The supported way to observe navigation, handle errors, or add caching. HttpCachePlugin, UrlWatcherPlugin, CatchEscapedLinksPlugin ship in scramjet-utils.

Prefix. The path all proxied URLs live under. __uv$config.prefix in Ultraviolet (one, global); controller.prefix + frameId in Scramjet 2.x (one per frame).

proxy-bootstrap. @mercuryworkshop/proxy-bootstrap. Resolves and caches its Scramjet package set at runtime, then serves everything the browser needs. The shortest path to a working proxy; fixes the transport at server start, so no runtime switching.

proxy-transports. @mercuryworkshop/proxy-transports. The interface transports implement (request and connect). Successor to bare-mux's transport interface; a direct dependency of Scramjet 2.x.

Rammerhead. A different proxy design, server-side session-based rather than service-worker-based. Occasionally works where interception proxies do not.

Rewriter. The component that transforms HTML, CSS and JavaScript so URLs and trapped globals point back through the proxy. Ultraviolet's is JavaScript; Scramjet's is Rust compiled to WebAssembly. Rewriting JavaScript correctly and quickly is the hard problem in this space.

Scramjet. The current-generation interception proxy from Mercury Workshop. Rust/WASM rewriter, wisp transport, frames and plugins. Successor to Ultraviolet.

Service worker. A browser-provided worker that can intercept network requests from pages on its origin and synthesise responses. The primitive the whole architecture rests on. Requires HTTPS, and has a scope that limits which URLs it controls.

SharedArrayBuffer. Memory shared between JavaScript and WebAssembly without copying. Disabled after Spectre; re-enabled only for cross-origin isolated pages. Scramjet needs it; Ultraviolet does not.

Session. Not an engine term. In this documentation's generated code, the uniform per-tab object that both engine adapters expose (go, back, forward, reload, destroy), so features work on either engine.

Transport. Client-side code that performs requests. epoxy, libcurl, bare. Chosen independently of the rewriter. See Transports.

Ultraviolet. The previous-generation interception proxy from TitaniumNetwork. JavaScript rewriter, bare-mux transports. Archived October 2024 at 3.2.10. Still widely deployed, and the option for an all-in-one build whose backend cannot host Wisp.

UrlWatcherPlugin. The Scramjet 2.x plugin that reports the real URL of a frame. There is no urlchange event; this is how you know where the page went. Fires for navigations, hash changes, and history.pushState.

Wisp. A multiplexing protocol carrying many TCP/UDP streams over one WebSocket. For HTTPS destinations, target TLS terminates in the browser and the relay sees ciphertext plus connection metadata. HTTP destinations are not encrypted end to end. Wisp requires a persistent WebSocket, which rules out most request/response serverless hosting. See Wisp vs Bare.

Source: docs/reference/glossary.md