Accept Header Builder

Run parsing, conversion, and validation in your browser. No input is sent to a server. Use it for first-pass format troubleshooting.

Status

Runs in your browser. No input is sent to a server. Use this as a first-pass diagnostic step.

How to use

Fill each field and click Build. Paste generated headers into client config or test requests to compare behavior.

Notes (this tool)

  • Final negotiation behavior depends on server implementation and content negotiation settings.
  • q values in Accept-Language are relative priorities. Ties may behave differently across implementations.

About this page

What does this tool do?

Builds Accept / Accept-Language / Accept-Encoding together and outputs copy-ready header lines.

Recommendations (practical)

  • Narrow Accept when possible
  • Use q values for language priority
  • Prefer br/gzip for encoding

Use-case guidance

  • API clients: narrow Accept to JSON-focused types to reduce unexpected MIME responses
  • Multilingual UI: keep Accept-Language to top 2–3 options with explicit q ordering
  • Compression testing: align Accept-Encoding with server support and verify with Content-Encoding
  • Accept-Language Inspect
  • Accept-Encoding Inspect

What this tool does

  • Build Accept* headers
  • Add q values

Notes

  • Overly broad Accept values can trigger unintended server defaults.
  • For negotiation issues, always inspect Vary alongside these headers.

Debugging workflow (recommended)

  • Paste target data
  • Run conversion or parsing and review results
  • Check delimiters, character encoding, and padding

Referenced specs

  • RFC 9110 (Accept / Accept-Language / Accept-Encoding)
  • RFC 9110 (Quality Values)

FAQ

Are q values required?

No. Use them when you need explicit priority ordering.

What happens if Accept is too broad?

You may receive unintended MIME variants, making troubleshooting harder.

References

  1. RFC 9110

These links are generated from site_map rules in recommended diagnostic order.

  1. Accept-Language Inspect — Parse Accept-Language and inspect language priority
  2. Content-Language Inspect — Parse Content-Language and inspect delivered locale
  3. Accept-Charset Inspect — Parse Accept-Charset and inspect charset preferences

Language/Locale

Compare Accept headers with Content-Language to debug negotiation mismatches