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Accept-Language

IANA permanent request RFC 9110 3 spellings

Declared by 90 providers across 3446 published specification files in the APIs.io network.

What this header is for, and how to use it →

A count here is providers whose published contract declares this header — not providers who send it. Response headers set at the edge rarely appear in an OpenAPI at all, so a low number can measure documentation practice rather than deployment.

Spelled 3 ways

HTTP field names are case-insensitive (RFC 9110 §5.1), so every spelling below is the same header on the wire. A contract is not the wire: generated clients key off the string, and a developer reading two of these sees two different headers.

Accept-Languageaccept-languageAccept-language

The registry

Statuspermanent
ReferenceRFC 9110, Section 12.5.4: HTTP Semantics

Providers declaring it (90)

acoustic adopets adp airbus-oneatlas algolia antavo apifreaks-api-hub-for-developers appdirect autodesk-bim360 autodesk-fusion back-market bamboo ccp-games cdk-global certifaction chaitin cisco-catalyst-center cisco-secure-firewall citi conekta credilinqai customer-io dow-jones dow-jones-developer-platform dtn ebay edamam-recipes elastic-path engineering-platform eurostat ev-energy eve-online factiva finalcad freepik genesys getty-images harvard harver ikea keyper lean-technologies london-stock-exchange-group mastercard mealie mention microsoft-azure moneris moodys-rms morningstar mx-platform mx-technologies newstore novopayment okta optimizely oracle-e-business-suite oracle-hospitality palenca-vech patch-io politecnico-di-torino punchh qliksense quandoo ripe-insurance rwth-aachen-university smart-pension smartnews tapcart tickitto top-group transit treadio tribe-payments university-of-helsinki uphold vendasta viator visa visier wallapop wazo who wikimedia wikipedia wikisource wiktionary wise zamna zhipu-ai

Explore

All headers Content Negotiation Guidance on headers.apievangelist.com

Work with this as data

Every header here is available over the APIs.io API and to AI agents over MCP. HTTP Headers is not yet its own endpoint on the v1 API. Reach it through catalog search and the tag graph, or the MCP server.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for http headers

3 MCP tools reach this
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
All 92 tools →

Call it yourself

curl for this page
Search the catalog
curl "https://apis.io/api/v1/search?q=accept-language&limit=10"
Everything under a tag
curl "https://apis.io/api/v1/tags/accept-language"

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