These are backing implementations of fetch:
- Chromium - https://source.chromium.org/chromium/chromium/src/+/master:third_party/blink/renderer/core/fetch/global_fetch.cc;l=57
- Deno - https://github.com/denoland/deno/tree/master/op_crates/fetch
- Fly - https://github.com/superfly/flyjs/tree/master/packages/v8env/src
- Node - https://github.com/node-fetch/node-fetch
- GitHub Polyfill - https://github.com/github/fetch
- Mozilla - https://github.com/mozilla/gecko-dev/tree/master/dom/fetch
- WebKit - https://github.com/WebKit/WebKit/tree/main/Source/WebCore/Modules/fetch