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api_key

de facto — unregistered request 2 spellings

Declared by 40 providers across 437 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 2 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.

api_keyAPI_KEY

Providers declaring it (40)

arize-ai bespoke-labs caplight companies-house contentstack depict depictai docparser doi dpla eve-online explorium fastforex foreign-agricultural-service frankieone hive hunter hunter-io levelblue lusha mage-ai mastercard moovit ncbi nih orange-health quandl similarweb sinay snackmagic structify telkomsel trail u-s-geological-survey us-geological-survey usda-agricultural-research-service-ars- usgs-water virto-commerce wordnik yext

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