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api-key

de facto — unregistered request 5 spellings

Declared by 93 providers across 4124 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 5 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-KeyAPI-KeyAPI-KEYApi-key

Providers declaring it (93)

activecampaign aeso affise apiops-cycles-canvas applovin appstorespy appyway arkham-intelligence azure-ai-foundry banzai breeze-chms brevo bridge cdisc configure8 connexpay contrast-security cosmose-ai d3 demio demodesk dev-to devto discourse famxplor-family-travel-api fincra fiserv getty-images greenly-earth helius hevy holidu hotelbeds hourone hypixel ideogram interhyp istock iterable kaleyra kontaktio kraken later lunchbox marginalia-search mavrck messaging-api microsoft microsoft-azure microsoft-azure-openai microsoft-azure-search mindbody murf national-weather-service netcracker neutrino-api new-relic noaa noaa-gov nord-security ontraport orders-api origin outdoorsy pay-i persons-api pinecone products-api prompt-armor pushpress qdrant quadrant-api respeecher ripe-insurance rocketlane rocketreach scale-computing sensors-data sentio shipmonk similarweb simpleanalytics smoobu soax streetmetrics supertokens the-predictive-index trint weather-gov weavr worldnewsapi xiaomi zora

Explore

All headers Authentication 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=api-key&limit=10"

Everything under a tag

curl "https://apis.io/api/v1/tags/api-key"

Discovery needs no key. Ratings and market analysis are Pro.

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