HTTP header viewer
CORS-limited. The browser only exposes headers the server allows via Access-Control-Expose-Headers. Most sites expose only a handful (e.g. content-type, content-length) or block the request entirely. For a complete header dump, use curl -I <url> locally.
About this tool
HTTP header viewer is a single-purpose utility on instant.tw, a free toolbox of calculators, converters, generators, and quick lookups. Everything works in your browser — nothing is uploaded, nothing is stored on a server unless explicitly noted.
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