Feature
API Key Authentication
Simple key-based authentication for server-to-server calls.
69 providers
324 APIs
68 declared variants
Authentication via an issued API key or secret passed in a header or query parameter. The lowest-friction path to a first successful call, and still the default for most machine-to-machine integrations.
69 API providers on the APIs.io network offer api key authentication. The highest-rated are OpenAI, Trello, Iterable, Healthie, UserGems.
Providers
Ranked by API Evangelist rating — Exemplar and Strong are expanded by default.
Exemplar 5 Complete, well-documented, and agent-ready
OpenAIOpenAI publishes a single unversioned REST API at https://api.openai.com/v1 covering text and reasoning (Re...TrelloTrello is a web-based, kanban-style, list-making application from Atlassian that lets teams organize tasks,...IterableIterable is an AI customer engagement platform that powers unified cross-channel marketing experiences and ...HealthieHealthie is a cloud, API-first EHR and practice management platform purpose-built for digital health startu...UserGemsUserGems is a San Francisco-based sales intelligence platform that tracks champion job changes and surfaces...
Strong 22 Solid coverage with minor gaps
EPA — U.S. Environmental Protection AgencyWeb services, data products, and open data spanning the U.S. Environmental Protection Agency. Programmatic ...PaperspacePaperspace is a GPU cloud platform for AI, ML, and 3D rendering workloads, acquired by DigitalOcean in 2023...PropelAuthPropelAuth is a B2B SaaS authentication and multi-tenant user management platform purpose-built for organiz...Apollo.ioApollo.io is a sales intelligence and go-to-market platform combining a database of 240M+ contacts and 30M+...CelestiaCelestia is the first production modular data availability blockchain. It separates consensus and data avai...Adafruit IOAdafruit IO is a cloud Internet of Things platform from Adafruit Industries built for makers, hobbyists, st...API LeagueAPI League is a single-key hub of 55 read-only HTTP APIs spanning twelve categories — Books, News, Humor, F...ThingSpeakThingSpeak is an IoT analytics platform from MathWorks that lets devices aggregate, visualize, and analyze ...ViamViam is a robotics and edge AI platform founded in 2020 by Eliot Horowitz (MongoDB co-founder and former CT...Arcade.devArcade.dev (formerly Arcade AI) is the MCP runtime for production AI agents — a platform that lets agents s...RocketReachRocketReach is a Seattle-based B2B contact data and sales intelligence provider that maintains a database o...ShipStationShipStation is a leading shipping platform for ecommerce businesses providing APIs to integrate shipping wo...IonQIonQ (NYSE IONQ) is a College Park, Maryland-based public trapped-ion quantum computing company. IonQ desig...Leonardo.AILeonardo.AI is an Australian generative-AI company (acquired by Canva in July 2024) offering a Production A...AdaptAdapt (adapt.io) is a B2B lead intelligence and sales acceleration platform that provides a database of 250...MindeeMindee is a document parsing and intelligent document processing platform. Its REST API (api-v2.mindee.net)...US Census BureauThe U.S. Census Bureau is the federal statistical agency responsible for producing data about the American ...AmplitudeAmplitude is a digital analytics platform that helps product teams understand user behavior, run experiment...SorsaSorsa Labs operates a real-time X (Twitter) data API providing developers access to tweets, profiles, searc...Track-PODTrack-POD is a cloud-based delivery management platform that combines route planning and optimization with ...CalendarificWorldwide public holidays REST API covering 230+ countries. Calendarific provides national, local, religiou...TrueworkTruework operates a unified income and employment verification platform for mortgage lenders, credit unions...
Developing 29 Usable, with meaningful gaps to close
GreenhouseGreenhouse Software is an enterprise applicant tracking system (ATS) and end-to-end hiring platform spannin...BandwidthBandwidth is a leading cloud-based communications platform providing voice, messaging, emergency calling, p...FactorialFactorial is an all-in-one HR, payroll, time, talent, finance, and IT management platform headquartered in ...Amazon Managed GrafanaAmazon Managed Grafana is a fully managed service for open source Grafana developed in collaboration with G...UbiquitiUbiquiti Inc. (NYSE: UI) is an American networking technology company that designs and sells wireless and w...TensorTensor is the Solana-native NFT marketplace and trading protocol founded by Tensor HQ and now stewarded by ...KushkiKushki is an Ecuador-headquartered LatAm fintech operating as a regional non-banking acquirer for the Andea...PostHogPostHog is an open source product analytics platform that provides event tracking, session recording, featu...VonageVonage (part of Ericsson) provides cloud communications APIs for voice, SMS, messaging, video, and verifica...VesselFinderVesselFinder is a maritime intelligence company operating a global AIS vessel-tracking network (terrestrial...ContinueContinue is the open-source AI code assistant for VS Code and JetBrains, distributed under Apache 2.0. The ...API SnapAPI Snap is a developer utility platform that consolidates 13+ commonly needed REST APIs into a single, uni...PolyAPIPoly, built using cutting-edge AI and Kubernetes-native technology, accelerates development and simplifies ...Aligned NewsAligned News is an AI-native intelligence and news platform that synthesizes AI-powered briefings from 63 c...FastDOLFederal workplace enforcement records on 2.3M US employers across 16 federal agencies — OSHA, WHD, MSHA, EP...OpsGenieOpsGenie is an incident management and alerting platform, now part of Atlassian, that helps operations team...StackOneStackOne is an AI-powered embedded integration platform as a service (iPaaS) designed to simplify and accel...TrackingMoreTrackingMore is a multi-carrier shipment tracking platform offering a unified REST API that integrates with...Australia PostAustralia Post is Australia's primary postal operator, offering a developer platform with REST APIs for e-c...Magic EdenMagic Eden is a multi-chain NFT marketplace offering REST and instruction-generation APIs for Solana, EVM c...Robin AIRobin AI is a London-headquartered legal intelligence platform founded in 2019 by former Clifford Chance di...NOAA — National Oceanic and Atmospheric AdministrationThe National Oceanic and Atmospheric Administration (NOAA) is the United States scientific and regulatory a...UnkeyUnkey is the developer platform for modern APIs, providing globally distributed API key management, rate li...Epidemic SoundEpidemic Sound is a Stockholm-based royalty-free music and sound effects licensing platform for video creat...TomTomTomTom provides a comprehensive suite of location technology APIs and SDKs including maps, search, routing,...TypesenseTypesense is a fast, typo-tolerant, open-source search engine designed for developer productivity. It provi...LangflowLangflow is an open-source low-code visual builder for AI agents, RAG pipelines, and LangChain-based workfl...RedisRedis is an open source, in-memory data structure store used as a database, cache, message broker, and stre...NASA Open APIsNASA Open APIs is the National Aeronautics and Space Administration's unified, public developer portal expo...
Thin 12 Limited public surface area
Chicago Transit AuthorityThe Chicago Transit Authority (CTA) is the public transit operator for the City of Chicago and 35 surroundi...Agricultural Statistics ServiceThe National Agricultural Statistics Service (NASS) is an agency of the United States Department of Agricul...LeverLever is a talent acquisition and applicant tracking platform built on the Opportunities data model. The Le...SyndicaSyndica is a Solana-only infrastructure company building developer infrastructure for Web3. Its production ...ElasticElastic is a software company that builds search-powered solutions for observability, security, and search ...io.netio.net is a decentralized GPU network for AI compute, built on Solana, that aggregates idle consumer and da...HoneycombBuild integrations and automate workflows with the Honeycomb API. Programmatically manage datasets, queries...Lemon SqueezyLemon Squeezy is on a mission to make selling digital products easy-peasy. We know first-hand the challenge...PaysafePaysafe is an integrated payment platform providing businesses with REST APIs for online payments, digital ...GreenlyGreenly is a Paris-headquartered (with offices in London and New York) carbon accounting platform focused o...Amazon AppSyncAmazon AppSync creates serverless GraphQL and Pub/Sub APIs that simplify application development through a ...Canada PostCanada Post is the primary postal operator in Canada, offering a developer platform with REST and SOAP web ...
Emerging 1 Early or largely undocumented
What Providers Actually Declared
This feature is a canonical term. These are the free-text strings
providers wrote in their own apis.yml that map onto it.
10 requests/second per API key with burst to 20 req/s (token bucket)30-day-rotation API keys for programmatic MCP accessAPI Key ApplicationAPI Key AuthenticationAPI Key IssuanceAPI Key Self-ServiceAPI Key TiersAPI KeysAPI Keys Post Expiration WindowAPI Keys: create, verify, list, update, deleteAPI key + secret authAPI key authenticationAPI key authentication via Api-Key header; keys generated and rotated from Account SettingsAPI key authentication via `x-api-key` header or query parameterAPI key authentication via the userkey query parameterAPI key authentication via the x-api-key header; keys are scoped to an explicit endpoint list or marked masterAPI keys (Bearer)API keys per environmentAPI-key authentication via `Authorization: Basic` + `AuthorizationSource: API` (plus `AuthorizationShard` for sharded customers)Authentication via `x-tensor-api-key` header issued through dev.tensor.trade after Airtable applicationAuthentication: API key via Tracking-Api-Key headerBasic Access Authorization using Base64-encoded API keyBearer auth with API keys prefixed con_Bearer-token API keys, prefixed tw_sk_ (production) and tw_sk_test_ (sandbox)Concurrency, queue, and rate-limit controls scoped per API keyEnd-user API keys (personal and org-scoped) with validation, usage stats, and import of legacy keysFree API KeyFree API key with no published rate limit; one key per email; required for all data queriesFree and open weather, climate, ocean, fisheries, and space-weather APIs — no payment required and most endpoints require no API keyFree developer program registration; API keys issued per environment (sandbox and production)Funded by TIA staking and PayForBlobs gas fees; no central API key or commercial pricing tierGenieKey-based authentication (per integration)Granular per-endpoint API key permissions (Harvest API)Header-based authentication (email + apiKey) with 250 requests-per-minute rate limitJWT and API key/secret authLocations API and Postage Assessment Calculator API keys obtainable via self-serve registration; no contract requiredMultiple API KeysMultiple authentication modes including API key, IAM, Cognito, and LambdaOAuth + API keysOAuth + API keys (project-scoped)
Showing 40 of 68 declared variants
Work with this as data
Every feature here is available over the APIs.io API and to AI agents over MCP. Features is not yet its own endpoint on the v1 API. Reach it through catalog search and the tag graph, or the MCP server.