Cookie Header Parser
Parse an HTTP Cookie request header into decoded name and value pairs.
Inspect Cookie request pairs as structured data
An HTTP Cookie request header is a semicolon-separated list of name and value pairs, which is easy to misread when values are encoded or empty. This parser walks the header while respecting quoted sections, splits each pair at its first equals sign, percent-decodes the value, and emits an ordered JSON array so duplicate names remain visible rather than overwriting one another.
The default header becomes three records: theme with dark, session with abc space 123, and flag with an empty value. A leading Cookie label is optional. An unclosed quote, a pair without an equals sign, an empty name, or malformed percent escape produces an explicit message instead of a partial object.
Request cookies are not Set-Cookie attributes
Cookie request headers do not include Path, Domain, SameSite, Secure, HttpOnly, or expiration attributes; those appear in Set-Cookie responses. Decoding percent escapes is useful for inspection but applications may use additional serialization conventions. Parsing happens only in your browser, so session values are not uploaded. Treat captured authentication cookies as secrets and redact them before sharing output.
Frequently Asked Questions
Why is the output an array instead of one object?
An array preserves order and duplicate cookie names, which an object would overwrite.
Does this parse Set-Cookie attributes?
No. It parses the Cookie request header; response attributes use different grammar and semantics.
Are percent-encoded values decoded?
Yes. Invalid percent escapes return an error rather than silently leaving ambiguous text.
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