Parse raw HTTP headers into normalized name-value pairs and highlight duplicates.
Headers
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Duplicates
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Bytes
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Enter the example value or paste your own input, choose the mode when one is available, and read the first result card for the direct answer. The output area gives a copyable block for code reviews, documentation, API tests, classwork or troubleshooting notes.
What the result means
The parser lowercases header names for counting and keeps the original values in JSON output.
What is not included
It parses pasted text only. It does not fetch a URL or validate server behavior.
Privacy note
The calculation runs in your browser. Avoid pasting production secrets, credentials, private keys, customer data or regulated personal data unless your own policy allows browser-based tools.