Guides: change HTTP headers in Chrome while you develop

Short, tested recipes for changing HTTP headers in Chrome while you develop. Each one lists the exact rules to type into Headrule, what cannot work and why, and the results of an automated test in Chromium.

• Fix a CORS error while developingAdd Access-Control-Allow-Origin and the preflight headers for one API, including requests with cookies.
• Add an Authorization header to every requestSend a Bearer token or Basic auth to a staging API, from fetch calls and the address bar.
• Load a page that refuses to be framedRemove X-Frame-Options and frame-ancestors, or keep the rest of the CSP.
• Switching from ModHeaderWhat happened, what to check in a replacement, and how to import your ModHeader export.