This page is controlled by a service worker that answers data.txt with the text "service worker". The file on the server says "network". Each worker fetches data.txt and reports the text it got. Every worker should report "service worker".
This is a reduced test case for WebKit bug 322883. As of 2026-Nov-12 the first test fails in Safari 27.0.1 on macOS and Safari 27.2 on iOS, and all three pass in Chrome and Firefox.
Download: webkit_bug_322883_repro.zip (this page, sw.js, worker.js, and data.txt). Serve the folder over HTTPS or from localhost, as a service worker needs one of those.
Starting...