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Idempotency & Reliability

Idempotency-Key

de facto — unregistered response 4 spellings

Declared by 127 providers across 4915 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 4 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.

Idempotency-Keyidempotency-keyIDEMPOTENCY-KEYIdempotency-key

Providers declaring it (127)

8x8 abound accessibe adyen ahasend airtm allowance anchorage ando apache-iceberg appsmax-rest-api-v1 archal augustus biolevate bizverify bolt-financial bridge causa-prima chariot cint coasty credilinqai cross-river dailypay debitura dedaluslabs deel-com diligent drivewealth dwolla elbo-ai-inc end-close evermuse fireblocks genesys golem-cloud goodstack gov-uk-pay h-company healthsherpa hevn-inc hm-land-registry humanitec jp-morgan-chase justifi kota lead-bank lean-technologies lemonmarkets lianlian-global lightspark lightspeed-pos lob lobcom loops loops-so lorum maia-analytics mastercard meow method-financial methodfi modern-treasury modernfi moengage mollie mydentify-public-api natural-ai newstore notyfi novu parseflow paywithmybank phasio plateiq prezent primitive processout qubiqle revolut rutter sail sail-research scalapay sendle sign-in-enterprise silna spaitial spaitial-ai speccheck spektr spree spree-commerce stablesea stedi subspace svix synctera terminal-use teya the-hog the-san-francisco-compute-company toss-payments totalis treasuryspring tribe-payments truelayer tvarka-atk-api unstoppable-finance upgrade usenarrative volt-io voltair wefunder withpersona workos worldpay xendit xero xquik-api yoco z-league zepto-payments zero-hash zest zest-equity zuora

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All headers Idempotency & Reliability Guidance on headers.apievangelist.com