Feature

WebSockets

Persistent bidirectional connections for live data.

41 providers 612 APIs 37 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.

41 API providers on the APIs.io network offer websockets. The highest-rated are Polygon, Postman, fal, Solana, Amazon API Gateway.

Providers

Ranked by API Evangelist rating — Exemplar and Strong are expanded by default.

Exemplar 10 Complete, well-documented, and agent-ready
Polygon Polygon (Polygon.io, rebranded as Massive in early 2026) provides real-time and historical market data APIs... 12 APIs 76.9 Postman Postman is the world's leading API platform, used by 35+ million developers to design, build, test, documen... 39 APIs 75.8 fal fal (Features and Labels, Inc.) is a generative media platform providing the world's fastest API for runnin... 12 APIs 75.1 Solana Solana is a high-performance blockchain platform designed for fast, secure, and scalable decentralized appl... 12 APIs 71.8 Amazon API Gateway Amazon API Gateway is a fully managed service that makes it easy to create, publish, maintain, monitor, and... 13 APIs 71.4 CryptoCompare CryptoCompare (now CoinDesk Data / CCData, acquired by CoinDesk in late 2024) is a long-standing crypto mar... 18 APIs 70.0 S&P Global S&P Global (NYSE SPGI) is the parent of S&P Global Ratings, S&P Global Market Intelligence, S&P Dow Jones I... 9 APIs 69.0 Kraken Kraken is one of the world's largest and longest-running cryptocurrency exchanges, founded in 2011 and head... 24 APIs 68.0 Medplum Medplum is an Apache 2.0 open-source, FHIR-native developer platform for shipping clinical software. It bun... 4 APIs 67.3 Cumulocity Cumulocity is an enterprise AIoT (Artificial Intelligence of Things) platform that connects, manages, and a... 39 APIs 66.7
Strong 10 Solid coverage with minor gaps
Modal Modal is a serverless cloud platform for AI and data workloads. Modal lets developers write ordinary Python... 17 APIs 64.8 Soracom Soracom is a global IoT cellular connectivity and platform provider headquartered in Tokyo, founded in 2014... 45 APIs 63.9 Inworld AI Inworld AI is a real-time voice AI infrastructure provider. The Inworld platform delivers text-to-speech, s... 7 APIs 61.6 Discord Discord is a voice, video and text communication service used by hundreds of millions of people to hang out... 29 APIs 61.5 Bloomberg AIM Bloomberg's Asset and Investment Manager (AIM) is a comprehensive buy-side solution offering global, multi-... 18 APIs 61.4 Encore Encore is a backend application framework and developer cloud that lets engineering teams build type-safe d... 6 APIs 61.4 Deepgram Deepgram is an enterprise voice AI platform that provides speech-to-text, text-to-speech, and voice agent A... 12 APIs 60.3 Triton One Triton One is a high-performance Solana RPC and blockchain infrastructure provider operating globally distr... 13 APIs 59.5 Backpack Backpack is a Solana-first crypto company founded by Armani Ferrante and Tristan Yver — the same team behin... 15 APIs 59.3 Amazon API Gateway Amazon API Gateway is a fully managed service that makes it easy for developers to create, publish, maintai... 18 APIs 58.3
Developing 11 Usable, with meaningful gaps to close
Tensor Tensor is the Solana-native NFT marketplace and trading protocol founded by Tensor HQ and now stewarded by ... 9 APIs 52.0 LBank LBank is a global cryptocurrency exchange providing REST and WebSocket APIs for spot trading, ETF/leveraged... 6 APIs 51.5 MEXC MEXC is a global cryptocurrency exchange providing REST and WebSocket APIs for spot trading, perpetual futu... 12 APIs 50.5 Binance Binance is the world's largest cryptocurrency exchange by trading volume, providing APIs for spot trading, ... 28 APIs 50.3 Akka Akka is a toolkit and runtime for building highly concurrent, distributed, and resilient message-driven app... 6 APIs 49.1 Blockdaemon Blockdaemon is an institutional blockchain infrastructure company founded in 2017 by Konstantin Richter. It... 11 APIs 48.9 Lunar Energy Lunar Energy is a Mountain View, California-based residential clean-energy company founded in August 2020 b... 14 APIs 48.9 elevenlabs Converts text into speech using a voice of your choice and returns audio. 22 APIs 46.1 NGINX NGINX is a high-performance open-source web server, reverse proxy, and API gateway widely used for load bal... 32 APIs 44.8 Apache Tomcat Apache Tomcat is an open-source implementation of the Java Servlet, JavaServer Pages (JSP), Java Expression... 5 APIs 44.7 Docling Docling is an open-source toolkit for parsing diverse document formats — PDF, DOCX, PPTX, XLSX, HTML, image... 18 APIs 44.0
Thin 6 Limited public surface area
celestia Celestia is the first production modular data availability blockchain. It separates consensus and data avai... 10 APIs 41.4 Amazon AppSync Amazon AppSync creates serverless GraphQL and Pub/Sub APIs that simplify application development through a ... 9 APIs 39.5 Loadsmart Loadsmart is a digital freight technology company and 4PL that connects shippers, carriers, warehouses, and... 48 APIs 38.7 BitMart BitMart is a global cryptocurrency exchange providing REST and WebSocket APIs for spot trading, perpetual f... 6 APIs 36.3 Syndica Syndica is a Solana-only infrastructure company building developer infrastructure for Web3. Its production ... 4 APIs 34.5 Bloomberg Professional Service Bloomberg Professional Service is a comprehensive financial data, news, and analytics platform serving inve... 9 APIs 31.7
Emerging 3 Early or largely undocumented
Artillery Artillery is an open source load testing and performance testing platform for APIs, microservices, and web ... 1 API 27.6 Cresta Cresta is a Mountain View / Sunnyvale, California contact center AI company spun out of the Stanford AI Lab... 25.5 Promptfoo Promptfoo is an open-source CLI and TypeScript/Node.js library for evaluating, red-teaming, and security-te... 20.9
Minimal 1 Almost no public developer surface
AutoGen Studio AutoGen Studio is a low-code / no-code developer GUI from Microsoft Research for rapidly prototyping, compo... 8.5

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)Custom providers via HTTP, WebSocket, Python, JavaScript, Go, Ruby, and ShellDocling 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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