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HTTP Prefer Header (RFC 7240) Parser / Builder

Network

Build an HTTP Prefer request-header value from a list of preferences with optional values and parameters, or parse an existing one, per RFC 7240

Add one or more preferences like respond-async, wait, or return with an optional value and parameters, and get back a ready-to-send Prefer header value with any non-token value automatically quoted per RFC 7240. Paste an existing Prefer header into the parser instead to see its preferences, values, and parameters broken out individually, useful when a REST API or async job endpoint supports optional preference negotiation and you want to confirm exactly what a client sent or a server should honor.

preferhttpheadersrfc7240content-negotiationrest-api

How to use HTTP Prefer Header (RFC 7240) Parser / Builder

  • 1.Add one or more preferences (a token like respond-async or return), each with an optional value and an optional parameter.
  • 2.Copy the generated Prefer header value, with any value that isn't a valid HTTP token quoted automatically.
  • 3.Paste an existing Prefer header into the parser field to see its preferences, values, and parameters broken out instead.

Frequently asked questions

What is the Prefer header actually used for?
RFC 7240 defines it for a client to ask a server to behave differently, for example respond-async to request an async 202 response, return=minimal to skip echoing a representation back, or wait=N to cap how long the server should wait before responding. A server is free to ignore any preference it doesn't support.
How does this tool decide whether to quote a value?
A value or parameter value is written bare only if it's a valid HTTP token (letters, digits, and a small set of symbols with no spaces). Anything else, like a value containing a space or comma, is wrapped in double quotes with any embedded quote escaped.
Does this tool validate that a preference is one the server or a library actually understands?
No, it only builds or parses the header's syntax per RFC 7240. It doesn't check the preference token against any registry or confirm a server actually supports it.
Does this make a network request?
No, it only builds or parses the header value locally. It doesn't send a request or check what a real server returns for any preference.

Use via API, SDK, or MCP

cURL# Free: 1,000 req/day · Pro: 10,000 req/day
curl -X POST https://api.utilix.tech/v1/tools/prefer-header \
  -H "Authorization: Bearer utx_live_..." \
  -H "Content-Type: application/json" \
  -d '{"preferences":[{"token":"respond-async"},{"token":"wait","value":"100"}],"header":"respond-async, return=minimal;handling=lenient"}'

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