HTTP Header Builder

Prepare consistent HTTP headers and them as raw HTTP, JSON, or Fetch syntax.

Enter one header per line as Name: value. The first colon separates the name from the content; later colons remain in the value, as in a URL. Blank lines are ignored. The engine trims surrounding whitespace, checks header-name characters and rejects prohibited control characters in values. A line without a name before the separator is rejected.

Header names are case-insensitive. When several lines name the same field, the last replaces earlier values and retains its final spelling. The counter counts normalized fields. This suits simple configuration but does not preserve every line of an HTTP response: distinct Set-Cookie fields cannot be faithfully represented in this object. Use the analyzer to inspect an existing block rather than applying this configuration merge.

HTTP output is a list of lines, JSON output an object and Fetch output a headers: {...} fragment for request options. No status, method or body is generated. JSON, cache and CORS presets are starting points to adapt. Access-Control-Allow-* fields belong in server responses; adding them to a request does not grant CORS permission. Some headers remain browser-controlled and can be refused when a real request is made.