HTTP Request Header Size Calculator

Estimate request-header and cookie byte size from pasted HTTP headers to debug 400 or 431 responses.

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This calculator helps debug oversized browser requests, especially when cookies grow until a proxy or server rejects the request. Paste request headers and compare the total size with a limit.

What it calculates

The report estimates header-block bytes, cookie bytes, largest headers and percentage of the selected limit used. It also breaks a Cookie header into individual cookie names.

Scope

Server limits vary by proxy, CDN and app server. The result is an estimate from the pasted text, not a live server test.