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If-Match

IANA permanent request RFC 9110 reached by regulation 3 spellings

Declared by 76 providers across 8764 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-Matchif-matchIF-MATCH

Reached by regulation

Basis: mandated. The law, or a technical standard the law makes binding, names this header. Visible in a published contract, which is what is counted here.

onc-health-it-certification

Carried by the fhir standard.

The registry

Status	permanent
Reference	RFC 9110, Section 13.1.1: HTTP Semantics

Providers declaring it (76)

8x8 akamai alliance-data-systems amazon-cloudfront amazon-s3 arangodb autodesk-fusion aws-s3 azure-storage-account azure-storage-accounts box cdk-global cint clerk-com clio cloudflare-r2 cloudfront commure cubefs cybersource dedaluslabs elastic-path engineering-platform equinix etsi forgerock galileo-technologies genesys glide-apps humanitec ibm ilert indykite interhyp jp-morgan-chase lakefs macrometa mastercard microsoft microsoft-azure microsoft-azure-kubernetes-service microsoft-azure-synapse-analytics microsoft-dynamics microsoft-dynamics-365 microsoft-dynamics-365-business-central microsoft-dynamics-365-sales microsoft-graph microsoft-planner microsoft-power-apps navision newstore nhost odata oracle oracle-database oracle-goldengate rook sap-s4hana sap-sales-and-distribution-sd siemens-mindsphere slashid subspace symphony synack tigris-data twilio uphold val-town veritas-netbackup vnc wikimedia wikipedia wikisource wiktionary wso2 zuora

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All headers Conditional Requests & Concurrency Guidance on headers.apievangelist.com