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If-None-Match

IANA permanent request RFC 9110 3 spellings

Declared by 102 providers across 2737 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.

If-None-MatchIF-NONE-MATCHif-none-match

The registry

Status	permanent
Reference	RFC 9110, Section 13.1.2: HTTP Semantics

Providers declaring it (102)

acoustic adobe adobe-premiere adobe-suite adp agicap aib-group-uk aldermore amazon-s3 apache-iceberg arangodb autodesk-fusion bank-of-ireland-uk bank-of-scotland barclays blng box brewpage btc-war-live-market-data-api ccp-games cdk-global cdr-energy chaitin cint clio cloudflare-r2 co-operative-bank commure continuous-delivery-foundation coventry-building-society devcycle eclipse edamam edamam-recipes electric-sql engineering-platform eve-online fenergo first-direct gb-bank genesys halifax here igaming-tools intersight lakefs lakekeeper leeds-building-society lloyds-banking-group macrometa mem metro-bank mettle microsoft-azure microsoft-azure-batch microsoft-azure-data-factory microsoft-azure-kubernetes-service microsoft-azure-synapse-analytics mojang monument-bank nationwide-building-society nedap nhost onshape open-banking-uk openfeature openmercantil oracle oracle-cloud oracle-database oracle-platforms osmaura paragon-bank phrase prefect principality-building-society quadrillion recognise-bank ringcentral rook santander-uk secure-trust-bank shawbrook-bank six-group skipton-building-society sovrn starling-bank thingsboard tigris-data tsb-bank uclouvain university-of-washington uphold val-town viglink virgin-money-uk viridi-parente wazo weatherbys-bank wikidata worldcat wso2

Explore

All headers Conditional Requests & Concurrency 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=if-none-match&limit=10"

Everything under a tag

curl "https://apis.io/api/v1/tags/if-none-match"

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