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Conditional Requests & Concurrency

If-None-Match

IANA permanent request RFC 9110 3 spellings

Declared by 76 providers across 1952 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

Statuspermanent
ReferenceRFC 9110, Section 13.1.2: HTTP Semantics

Providers declaring it (76)

agicap aib-group-uk aldermore amazon-s3 apache-iceberg arangodb autodesk-fusion aws-s3 bank-of-ireland-uk bank-of-scotland box brewpage ccp-games cdk-global cdr-energy chaitin cint clio cloudflare-r2 co-operative-bank commure coventry-building-society devcycle edamam edamam-recipes electric-sql engineering-platform eve-online first-direct gb-bank genesys halifax lakefs leeds-building-society lloyds-banking-group macrometa mem metro-bank mettle microsoft-azure microsoft-azure-kubernetes-service microsoft-azure-synapse-analytics mojang monument-bank nationwide-building-society nhost onshape open-banking-uk openfeature oracle oracle-database paragon-bank phrase prefect principality-building-society quadrillion recognise-bank ringcentral rook santander-uk secure-trust-bank shawbrook-bank six-group skipton-building-society starling-bank thingsboard tigris-data tsb-bank uphold val-town viglink virgin-money-uk weatherbys-bank wikidata worldcat wso2

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