Feature
WebSockets
Persistent bidirectional connections for live data.
40 providers
215 APIs
36 declared variants
A WebSocket channel pushes updates to clients without polling. Essential for market data, chat, presence, collaborative editing, and any interface that has to feel live.
40 API providers on the APIs.io network offer websockets. The highest-rated are Medplum, Kraken, Solana, Polygon, fal.
Providers
Ranked by API Evangelist rating — Exemplar and Strong are expanded by default.
Exemplar 8 Complete, well-documented, and agent-ready
MedplumMedplum is an Apache 2.0 open-source, FHIR-native developer platform for shipping clinical software. It bun...KrakenKraken is one of the world's largest and longest-running cryptocurrency exchanges, founded in 2011 and head...SolanaSolana is a high-performance blockchain platform designed for fast, secure, and scalable decentralized appl...PolygonPolygon (Polygon.io, rebranded as Massive in early 2026) provides real-time and historical market data APIs...falfal (Features and Labels, Inc.) is a generative media platform providing the world's fastest API for runnin...S&P GlobalS&P Global (NYSE SPGI) is the parent of S&P Global Ratings, S&P Global Market Intelligence, S&P Dow Jones I...PostmanPostman is the world's leading API platform, used by 35+ million developers to design, build, test, documen...Inworld AIInworld AI is a real-time voice AI infrastructure provider. The Inworld platform delivers text-to-speech, s...
Strong 5 Solid coverage with minor gaps
Amazon API GatewayAmazon API Gateway is a fully managed service that makes it easy to create, publish, maintain, monitor, and...ModalModal is a serverless cloud platform for AI and data workloads. Modal lets developers write ordinary Python...CumulocityCumulocity is an enterprise AIoT (Artificial Intelligence of Things) platform that connects, manages, and a...BackpackBackpack is a Solana-first crypto company founded by Armani Ferrante and Tristan Yver — the same team behin...EncoreEncore is a backend application framework and developer cloud that lets engineering teams build type-safe d...
Developing 17 Usable, with meaningful gaps to close
Lunar EnergyLunar Energy is a Mountain View, California-based residential clean-energy company founded in August 2020 b...TensorTensor is the Solana-native NFT marketplace and trading protocol founded by Tensor HQ and now stewarded by ...CryptoCompareCryptoCompare (now CoinDesk Data / CCData, acquired by CoinDesk in late 2024) is a long-standing crypto mar...SoracomSoracom is a global IoT cellular connectivity and platform provider headquartered in Tokyo, founded in 2014...Amazon API GatewayAmazon API Gateway is a fully managed service that makes it easy for developers to create, publish, maintai...Bloomberg AIMBloomberg's Asset and Investment Manager (AIM) is a comprehensive buy-side solution offering global, multi-...Triton OneTriton One is a high-performance Solana RPC and blockchain infrastructure provider operating globally distr...DeepgramDeepgram is an enterprise voice AI platform that provides speech-to-text, text-to-speech, and voice agent A...BlockdaemonBlockdaemon is an institutional blockchain infrastructure company founded in 2017 by Konstantin Richter. It...DiscordDiscord is a voice, video and text communication service used by hundreds of millions of people to hang out...MEXCMEXC is a global cryptocurrency exchange providing REST and WebSocket APIs for spot trading, perpetual futu...LBankLBank is a global cryptocurrency exchange providing REST and WebSocket APIs for spot trading, ETF/leveraged...BinanceBinance is the world's largest cryptocurrency exchange by trading volume, providing APIs for spot trading, ...Apache TomcatApache Tomcat is an open-source implementation of the Java Servlet, JavaServer Pages (JSP), Java Expression...DoclingDocling is an open-source toolkit for parsing diverse document formats — PDF, DOCX, PPTX, XLSX, HTML, image...NGINXNGINX is a high-performance open-source web server, reverse proxy, and API gateway widely used for load bal...LoadsmartLoadsmart is a digital freight technology company and 4PL that connects shippers, carriers, warehouses, and...
Thin 9 Limited public surface area
SyndicaSyndica is a Solana-only infrastructure company building developer infrastructure for Web3. Its production ...celestiaCelestia is the first production modular data availability blockchain. It separates consensus and data avai...AkkaAkka is a toolkit and runtime for building highly concurrent, distributed, and resilient message-driven app...elevenlabsConverts text into speech using a voice of your choice and returns audio.Amazon AppSyncAmazon AppSync creates serverless GraphQL and Pub/Sub APIs that simplify application development through a ...Bloomberg Professional ServiceBloomberg Professional Service is a comprehensive financial data, news, and analytics platform serving inve...ArtilleryArtillery is an open source load testing and performance testing platform for APIs, microservices, and web ...CrestaCresta (legally Cresta Intelligence, Inc.) is a Palo Alto, California enterprise Customer Experience AI com...BitMartBitMart is a global cryptocurrency exchange providing REST and WebSocket APIs for spot trading, perpetual f...
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.
API Client (HTTP, GraphQL, gRPC, WebSocket, MQTT, Socket.io)Docling Serve HTTP API with sync and async endpoints, WebSocket task streaming, and zip-bundle outputGateway WebSocket for realtime eventsHTTP and WebSocketHTTP/WebSocket wrapper for BLPAPIInternal FastAPI surface (not a public API) under `/api/` with routes for teams, sessions, runs, gallery, mcp, settings, validation, and a `/api/ws` WebSocket for streamingNotification 2.0 — high-throughput, ordered, persistent WebSocket streaming with JWT-token auth and per-subscriber bufferingPublic + authenticated WebSocket streams for market data, order updates, position updates, and RFQRaw endpoints (api.raw) for webhooks and low-level HTTP, plus streaming endpoints for WebSocketsReal-time WebSocket streamerReal-time WebSocket transcription companion to the Scribe batch APIsReal-time subscriptions via WebSocket connectionsShared and Dedicated JSON-RPC + WebSocket nodes for Bitcoin, Ethereum, Solana, Polygon, Arbitrum, Avalanche, Base, Optimism, Cosmos, Polkadot, NEAR, Cardano, Stellar, XRP, Tron, Monad, Hyperliquid, and moreSolana JSON-RPC PubSub over WebSocket — accountSubscribe, programSubscribe, signatureSubscribe, slotSubscribe, blockSubscribe, logsSubscribe, rootSubscribeSoracom Beam — cloud proxy for TLS termination and HTTP/MQTT/TCP/UDP/WebSocket protocol conversionSubscriptions (Webhooks + Websockets)Subspace real-time WebSocket API streaming dock appointment eventsSynchronous, asynchronous queue, server-sent streaming, and WebSocket realtime invocation modesVoice transport via SIP trunking, PSTN transfer, CCaaS native streaming, WebSocket, gRPC, and raw RTPWeb Endpoints via FastAPI, ASGI, WSGI, and custom web servers — streaming and WebSocketsWebSocket API SupportWebSocket APIsWebSocket Streaming for Live Market DataWebSocket StreamsWebSocket SubscriptionsWebSocket SupportWebSocket TTS for bidirectional streaming synthesisWebSocket and Socket.IO TestingWebSocket clusters per asset classWebSocket streaming for low-latency synthesisWebSocket streaming for real-time STTWebSocket subscriptions for `newTransaction`, `ammOrderUpdate`, `tcompBidUpdate`, with ping/unsubscribe control framesWebSocket subscriptions for blob.Subscribe, header.Subscribe, fraud.SubscribeWebSocket telemetry streamsWebSocket v2 with Authenticated TradingWhirligig WebSocket with transactionSubscribe — the missing Solana subscription
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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.