Transport conformance

Each behaviour below runs the same test code on every adapter rust-fetch has: both Node.js transports, fetch() in Node.js (the browser build without the Node.js entry), and real browsers. ✓ is the expected behaviour; "differs" is a documented difference, explained under the table. Generated by npm run test:conformance (wasm-module/js/test/conformance/), which fails CI on any other difference. The Rust client is covered by its own integration tests.

Redirects

Behaviour	node:http	native	fetch() in Node.js	Chromium	Firefox	WebKit
GET through a 301 is followed	✓	✓	✓	✓	✓	✓
GET through a 302 is followed	✓	✓	✓	✓	✓	✓
GET through a 303 is followed	✓	✓	✓	✓	✓	✓
GET through a 307 is followed	✓	✓	✓	✓	✓	✓
GET through a 308 is followed	✓	✓	✓	✓	✓	✓
POST through a 301 becomes GET, without a body	✓	✓	✓	✓	✓	✓
POST through a 302 becomes GET, without a body	✓	✓	✓	✓	✓	✓
POST through a 303 becomes GET, without a body	✓	✓	✓	✓	✓	✓
POST through a 307 becomes POST with its body	✓	✓	✓	✓	✓	✓
POST through a 308 becomes POST with its body	✓	✓	✓	✓	✓	✓
PUT through a 303 becomes GET without a body	✓	✓	✓	✓	✓	✓
Authorization is dropped on a cross-origin redirect, kept on a same-origin one	✓	✓	✓	✓	✓	✓
sensitiveHeaders are dropped on a cross-origin redirect	✓	✓	differs (1)	differs (1)	differs (1)	differs (1)
maxRedirects: 2 stops a third redirect	✓	✓	differs (2)	differs (2)	differs (2)	differs (2)
A redirect loop fails	✓	✓	✓	✓	✓	✓
redirect: 'manual' returns the 3xx	✓	✓	✓	differs (3)	differs (3)	differs (3)
redirect: 'error' rejects a redirect	✓	✓	✓	✓	✓	✓
A redirect to another scheme (data:) is refused	✓	✓	✓	✓	✓	✓

Decompression

Behaviour	node:http	native	fetch() in Node.js	Chromium	Firefox	WebKit
gzip is decoded	✓	✓	✓	✓	✓	✓
deflate is decoded	✓	✓	✓	✓	✓	✓
br is decoded	✓	✓	✓	✓	✓	✓
A corrupt gzip body fails	✓	✓	✓	✓	✓	differs (4)
A 64 MB gzip bomb stops at maxResponseBytes	✓	✓	✓	✓	✓	✓

Size limits

Behaviour	node:http	native	fetch() in Node.js	Chromium	Firefox	WebKit
maxResponseBytes: exactly at the limit passes, one byte more fails	✓	✓	✓	✓	✓	✓
maxResponseBytes errors a streamed body once it passes the limit	✓	✓	✓	✓	✓	✓

Timeouts and cancellation

Behaviour	node:http	native	fetch() in Node.js	Chromium	Firefox	WebKit
A timeout before the headers is a TimeoutError	✓	✓	✓	✓	✓	✓
The timeout covers reading the body	✓	✓	✓	✓	✓	✓
An already-aborted signal rejects without sending	✓	✓	✓	✓	✓	✓
Aborting while waiting for the response is a CancelledError	✓	✓	✓	✓	✓	✓
Aborting mid-stream errors the body with a CancelledError	✓	✓	✓	✓	✓	✓

Errors

Behaviour	node:http	native	fetch() in Node.js	Chromium	Firefox	WebKit
A refused connection is a NetworkError	✓	✓	✓	✓	✓	✓
A 404 is an HttpError with the status	✓	✓	✓	✓	✓	✓
Malformed JSON falls back to text by default	✓	✓	✓	✓	✓	✓
Malformed JSON with responseType: 'json' is a ParseError	✓	✓	✓	✓	✓	✓
CR/LF in a header value is an InvalidInputError, before sending	✓	✓	✓	✓	✓	✓
A 503 is retried, and the retry succeeds	✓	✓	✓	✓	✓	✓

Streaming

Behaviour	node:http	native	fetch() in Node.js	Chromium	Firefox	WebKit
A streamed body arrives in full	✓	✓	✓	✓	✓	✓
A connection dropped mid-body errors the stream with a NetworkError	✓	✓	✓	✓	✓	✓
A slow reader of a streamed body holds the server back, and cancel() closes the connection	✓	✓	✓	differs (5)	differs (5)	differs (5)
A slow reader of NDJSON holds the server back, and cancel() closes the connection	✓	✓	✓	differs (5)	differs (5)	differs (5)
Aborting mid-stream closes the connection	✓	✓	✓	✓	✓	✓
maxResponseBytes reached mid-stream closes the connection	✓	✓	✓	✓	✓	✓
NDJSON: \n and \r\n, empty lines skipped, a last line without a newline	✓	✓	✓	✓	✓	✓
maxLineBytes: the lines before a long one, then a NetworkError	✓	✓	✓	✓	✓	✓
Server-Sent Events: types, ids and multi-line data, until [DONE]	✓	✓	✓	✓	✓	✓
maxEventBytes: the events before a large one, then a NetworkError	✓	✓	✓	✓	✓	✓

URLs

Behaviour	node:http	native	fetch() in Node.js	Chromium	Firefox	WebKit
baseUrl joining, relative paths and query parameters encode the same everywhere	✓	✓	✓	✓	✓	✓

Security

Behaviour	node:http	native	fetch() in Node.js	Chromium	Firefox	WebKit
Paths like //host stay under baseUrl	✓	✓	✓	✓	✓	✓
allowAbsoluteUrls: false refuses an absolute URL, before sending	✓	✓	✓	✓	✓	✓
allowPrivateNetwork: false blocks 127.0.0.1, before sending	✓	✓	differs (6)	differs (6)	differs (6)	differs (6)
maxPendingRequests refuses one more, without sending it	✓	✓	✓	✓	✓	✓
retryBudget refuses a retry, keeping the attempt’s error	✓	✓	✓	✓	✓	✓

Documented differences

1. fetch() follows redirects itself, so sensitiveHeaders can't apply (documented)
2. fetch() has no redirect-limit option; it applies its own limit (20) instead (documented)
3. browsers return an opaque redirect: status 0 and an empty body (documented)
4. WebKit decodes responses itself: on macOS a corrupt gzip body fails, but on Linux (libsoup) it's passed through as it arrived, which rust-fetch can't detect
5. browsers read a response ahead of the page themselves, however slowly it's consumed: their own fetch() took 59–64 MB of 64 in this test, as rust-fetch did; how far varies by browser and machine
6. only the Node.js entry checks addresses; browsers enforce their own private-network rules (documented)