Feature
WebSockets
Persistent bidirectional connections for live data.
37 providers
231 APIs
33 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.
37 API providers on the APIs.io network offer websockets. The highest-rated are Postman, ElevenLabs, Medplum, Amazon API Gateway, Cumulocity.
Providers
Ranked by API Evangelist rating — Exemplar and Strong are expanded by default.
Exemplar 5 Complete, well-documented, and agent-ready
PostmanPostman is the world's leading API platform, used by 35+ million developers to design, build, test, documen...ElevenLabsElevenLabs is an AI research and product company building voice and audio models, founded in 2022 and launc...MedplumMedplum is an Apache 2.0 open-source, FHIR-native developer platform for shipping clinical software. It bun...Amazon API GatewayAmazon API Gateway is a fully managed service that makes it easy to create, publish, maintain, monitor, and...CumulocityCumulocity is an enterprise AIoT (Artificial Intelligence of Things) platform that connects, manages, and a...
Strong 9 Solid coverage with minor gaps
falfal (Features and Labels, Inc.) is a generative media platform providing the world's fastest API for runnin...Massive (formerly Polygon.io)Polygon (Polygon.io, rebranded as Massive in early 2026) provides real-time and historical market data APIs...KrakenKraken is one of the world's largest and longest-running cryptocurrency exchanges, founded in 2011 and head...CelestiaCelestia is the first production modular data availability blockchain. It separates consensus and data avai...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...SolanaSolana is a high-performance blockchain platform designed for fast, secure, and scalable decentralized appl...LoadsmartLoadsmart is a digital freight technology company and 4PL that connects shippers, carriers, warehouses, and...ArtilleryArtillery is an open source load testing and performance testing platform for APIs, microservices, and web ...BlockdaemonBlockdaemon is an institutional blockchain infrastructure company founded in 2017 by Konstantin Richter. It...
Developing 10 Usable, with meaningful gaps to close
EncoreEncore is a backend application framework and developer cloud that lets engineering teams build type-safe d...DeepgramDeepgram is an enterprise voice AI platform that provides speech-to-text, text-to-speech, and voice agent A...Triton OneTriton One is a high-performance Solana RPC and blockchain infrastructure provider operating globally distr...SoracomSoracom is a global IoT cellular connectivity and platform provider headquartered in Tokyo, founded in 2014...DiscordDiscord is a voice, video and text communication service used by hundreds of millions of people to hang out...CryptoCompareCryptoCompare (now CoinDesk Data / CCData, acquired by CoinDesk in late 2024) is a long-standing crypto mar...NGINXNGINX is a high-performance open-source web server, reverse proxy, and API gateway widely used for load bal...Bloomberg AIMBloomberg's Asset and Investment Manager (AIM) is a comprehensive buy-side solution offering global, multi-...BackpackBackpack is a Solana-first crypto company founded by Armani Ferrante and Tristan Yver — the same team behin...TensorTensor is the Solana-native NFT marketplace and trading protocol founded by Tensor HQ and now stewarded by ...
Thin 11 Limited public surface area
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...Lunar EnergyLunar Energy is a Mountain View, California-based residential clean-energy company founded in August 2020 b...SyndicaSyndica is a Solana-only infrastructure company building developer infrastructure for Web3. Its production ...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...Amazon AppSyncAmazon AppSync creates serverless GraphQL and Pub/Sub APIs that simplify application development through a ...AkkaAkka is a toolkit and runtime for building highly concurrent, distributed, and resilient message-driven app...CrestaCresta (legally Cresta Intelligence, Inc.) is a Palo Alto, California enterprise Customer Experience AI com...Bloomberg Professional ServiceBloomberg Professional Service is a comprehensive financial data, news, and analytics platform serving inve...
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 RTPWebSocket APIsWebSocket Streaming for Live Market DataWebSocket StreamsWebSocket SubscriptionsWebSocket SupportWebSocket 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
Scroll for all 33
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.