A WebSocket handshake carries the no-cache pair every browser sends
The WebSocket upgrade request carries both Pragma: no-cache and Cache-Control: no-cache. Information only (severity: info).
What a detector infers
A WebSocket connection starts as an HTTP request that is never cacheable, and browsers mark it that way. In Chromium the handshake is sent with load flags that switch the cache off, and the HTTP transaction layer turns those flags into two headers, Pragma: no-cache and Cache-Control: no-cache, unconditionally. Every browser measured sends the pair on its upgrade request.
A WebSocket client that is not a browser — a library opening the same connection while presenting a browser's user agent and origin — has to add them on purpose. The probe opens a WebSocket to the audit's own endpoint and reads the headers on the server side, where page script can neither see nor change them. Only one side is measured: the pair was present on every arm tested and no failing client was captured, so the row is information only.
A TLS-terminating proxy that rewrites request headers could also change it, which is one more reason not to score it.
How to resolve it
Nothing to fix in a browser: the headers are added below JavaScript. A non-browser WebSocket client presenting itself as one shows here and in the rest of its handshake; open the connection from the browser instead.
Nearby checks in HTTP request vs the runtime
- Client hints on the wire carry the values JavaScript reports
client-hints-wire-vs-jsA server that asks for client hints with Accept-CH receives, on the next request, headers that describe facts JavaScript can also read… - The image Accept header is the one the claimed Chrome major sends
image-accept-vs-claimed-majorThe Accept header Chrome sends for an <img> is compiled from the image formats the build decodes by default, and it changed at 155: JPEG XL… - A cacheable resource fetched twice comes from cache the second time
http-cache-honouredA browser that is allowed to cache a response does. The probe fetches an immutable, cacheable resource unique to this visit twice, then… - Accept-Language leads with the same language as navigator.languages
accept-language-vs-navigatorAccept-Language and navigator.languages are two views of one browser preference: the header is serialised by the network stack, the array is… - Global Privacy Control reads the same in the page, in a worker and on the wire
gpc-header-vs-navigatorGlobal Privacy Control has three faces: navigator.globalPrivacyControl in the window, the same property in workers, and the Sec-GPC: 1… - The client-hint headers match navigator.userAgentData
sec-ch-ua-vs-uadataUser-Agent Client Hints exist in two places at once, which is what makes them checkable. - Sec-Fetch-* describes the request this page actually made
sec-fetch-metadataSec-Fetch-Site, Sec-Fetch-Mode and Sec-Fetch-Dest are attached by the browser to describe the request's own provenance — where it came from… - The order your browser emits its HTTP headers in
http-header-order-readoutA browser emits its request headers in a fixed sequence compiled into its network stack, and that sequence differs between engines…
Clearcote is a browser built for fingerprint coherence
It is a Chromium fork, maintained by the same people who wrote this reference. It ships as a compiled browser rather than as a stealth script injected into someone else's — which is a description of how it is built, and is not an argument about how it behaves on this check.
This audit takes no position on how Clearcote scores on HTTP request vs the runtime checks, on this one, or anywhere else. It has no baseline corpus of other people's fingerprints to rank you against and no vendor scoreboard — nearly every check is self-referential, asking one browser the same question through two independent APIs and reporting whether both answers can be true at once. It runs identically on any browser, including ours. Run it on yours and read the result yourself.
See the other checks in HTTP request vs the runtime — the family websocket-handshake-no-cache belongs to.