Realtime
A topic catalog of realtime APIs, protocols, providers, and patterns. Realtime distinguishes itself from streaming by being interactive and typically bidirectional — channels, presence, signaling, and message envelopes flowing in both directions between clients and servers — where streaming is one-way firehose delivery. This index documents the major realtime protocols (WebSocket, Server-Sent Events, WebRTC, MQTT, CoAP, gRPC streaming, GraphQL Subscriptions), hosted realtime providers (Ably, Pusher, PubNub, LiveKit, Daily, Agora, Twilio, Vonage, Amazon IVS, Cloudflare Realtime), open-source frameworks (Socket.IO), and push notification systems (OneSignal, FCM, APNs, Web Push, Pushwoosh).
Resources
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WebSocket
A full-duplex communication protocol over a single TCP connection, standardized by the IETF as RFC 6455 and defined in the WHATWG WebSocket API on the client side. WebSocket is the most widely deployed realtime protocol on the web — used f…
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Server-Sent Events (SSE)
A unidirectional server-to-client streaming protocol over HTTP, defined by the WHATWG HTML Living Standard. SSE is simpler than WebSocket — it reuses HTTP and supports automatic reconnection — but is one-way only. It has seen a resurgence…
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WebRTC
A peer-to-peer realtime communication framework for audio, video, and arbitrary data channels, standardized by the W3C and IETF. WebRTC defines an SDP-based offer/answer signaling model, ICE/STUN/TURN for NAT traversal, SRTP for media, and…
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MQTT
A lightweight publish/subscribe protocol standardized by OASIS, designed for constrained devices and low-bandwidth networks. MQTT is the dominant realtime protocol in IoT, used by AWS IoT Core, Azure IoT Hub, Google Cloud IoT, HiveMQ, EMQX…
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CoAP
The Constrained Application Protocol, defined in IETF RFC 7252, is a RESTful protocol for constrained devices over UDP, with an Observe extension (RFC 7641) that provides realtime resource notification. CoAP is used in industrial IoT and L…
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gRPC Streaming
gRPC supports four call patterns — unary, server streaming, client streaming, and bidirectional streaming — all carried over HTTP/2. gRPC streams are widely used for internal service-to-service realtime communication, with gRPC-Web bridgin…
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GraphQL Subscriptions
A GraphQL operation type that delivers realtime updates to clients, typically carried over WebSocket using the graphql-ws or legacy graphql-transport-ws protocol, or over SSE using the GraphQL-SSE protocol. Subscriptions are supported by A…
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WebTransport
A modern web API built on HTTP/3 and QUIC providing bidirectional and unidirectional streams plus unreliable datagrams to browsers. Designed as a higher-performance successor to WebSocket for streaming workloads, supported in Chromium-base…
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Ably
A hosted realtime platform offering Pub/Sub Channels, Chat, Spaces, LiveObjects, LiveSync, and AI Transport — built on a global edge network with low-latency multiprotocol fanout (WebSocket, MQTT, SSE, HTTP). Anchored by the documentation…
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PubNub
A realtime platform offering Pub/Sub messaging, Presence detection, Chat SDKs, Functions (serverless), Events & Actions, Insights analytics, BizOps Workspace, Illuminate, and an Admin API. PubNub markets "Send a message via API and have it…
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Pusher
A hosted realtime API from MessageBird offering two products — Channels (pub/sub messaging) and Beams (push notifications) — under the framing "Our hosted APIs are flexible, scalable, and easy to integrate." Pusher Channels uses a propriet…
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LiveKit
An open-source WebRTC platform marketed as "The platform for voice, video, and physical AI agents." LiveKit ships an SFU media server, Agents framework for production realtime AI, server SDKs in Go/Node/Python/Ruby, and client SDKs for Jav…
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Daily
A WebRTC video API provider offering Prebuilt embeddable video rooms, a Client SDK for custom apps, and Realtime Transport for AI Agents — the underlying infrastructure for Pipecat-deployed voice agents. Daily frames Pipecat as "a vendor-n…
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Agora.io
A realtime engagement platform offering Video Calling, Voice Calling, Signaling, Chat, and a Conversational AI Engine, framed as building "cutting-edge, voice-enabled applications by merging Agora's robust real-time audio streaming with th…
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Twilio Video / Live
Twilio's realtime video and live streaming products. Twilio Video provides WebRTC-based group rooms and peer rooms; Twilio Live (in select markets) layers low-latency interactive live streaming on top. Both share Twilio's identity, access…
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Vonage Video API
A WebRTC video API (formerly TokBox / OpenTok) for embedding live video, audio, and screen sharing into web and mobile apps. Provides session/token-based access control, multiparty rooms, broadcasting, archiving, and SIP interop.
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Amazon Interactive Video Service (IVS)
AWS's low-latency interactive video service. IVS Real-Time Streaming offers WebRTC-based stages for multi-host interactivity; IVS Low-Latency Streaming offers HLS-based one-to-many delivery. IVS Chat provides a managed realtime chat servic…
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Cloudflare Realtime
Cloudflare's realtime media stack — RealtimeKit (SDKs and APIs for live video/voice), the Realtime SFU ("a powerful media server that efficiently routes video and audio"), and a managed TURN Service for WebRTC NAT traversal over UDP/TCP/TL…
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Socket.IO
A widely deployed open-source realtime engine for Node.js (with clients across JavaScript, Java, Swift, Kotlin, .NET, Python) that layers reconnection, rooms, namespaces, and binary support on top of WebSocket (with HTTP long-polling fallb…
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Phoenix Channels
The realtime layer of the Elixir Phoenix Framework — soft-realtime channels, presence, and pub/sub built on the BEAM VM. Channels carry WebSocket (or long-poll fallback) topics with broadcast/subscribe semantics; Phoenix Presence implement…
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Centrifugo
An open-source language-agnostic realtime messaging server providing WebSocket, SSE, HTTP streaming, and WebTransport transports with channel-based pub/sub, presence, history, and JWT-based access tokens. Designed to offload realtime fanou…
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OneSignal
A multichannel customer messaging platform with Push (mobile + web), Email, SMS & RCS, and In-App Messages — framed as letting teams "set up and send mobile and web push notifications with advanced targeting and automation." Provides REST…
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Firebase Cloud Messaging (FCM)
Google's cross-platform push notification and message delivery service for Android, iOS, and web. FCM uses HTTP v1 API for server-to-FCM message submission and a long-lived connection (XMPP-derived on Android, APNs for iOS, Web Push for br…
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Apple Push Notification Service (APNs)
Apple's push notification system for iOS, iPadOS, macOS, tvOS, watchOS, and visionOS. APNs uses an HTTP/2-based provider API with token-based or certificate-based authentication for server-to-Apple delivery, and a persistent device connect…
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Web Push API
An IETF-standardized push system for the web, comprising the W3C Push API (browser-side subscription), the IETF Web Push Protocol (RFC 8030, server-to-push-service delivery), and Message Encryption for Web Push (RFC 8291). Routed via vendo…
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Pushwoosh
A customer engagement platform offering push notifications (mobile + web), in-app messaging, email, and SMS with segmentation, journeys, and a Customer Journey Builder. Uses native vendor push gateways (FCM, APNs, Web Push) under the hood.
Links
Providers working in Realtime
Providers whose own tags share at least two of this topic's tags, most shared first — the top 30 of 90.
| Provider | About | Rating | APIs |
|---|---|---|---|
| HiveMQ | HiveMQ is an enterprise MQTT broker and IoT connectivity platform that provides reliable, scalable bidirectional messaging between connected devices and back-end systems using the MQTT protocol. It supports MQTT 3, MQTT 5, MQTT over WebSoc… | developing | 1 |
| Ably | Ably is a realtime messaging platform offering pub/sub, presence, push notifications, chat, LiveSync, and integrations over WebSocket and HTTP. Ably publishes its OpenAPI specifications publicly via the ably/open-specs GitHub repository, w… | developing | 2 |
| Pusher | Pusher is a realtime communication platform owned by MessageBird/Bird. Its primary product Channels provides pub/sub messaging over WebSocket and HTTP; Beams provides device push notifications. Authentication uses an app key + secret per P… | thin | 1 |
| PubNub | PubNub is a realtime communication platform supporting pub/sub, presence, chat, App Context (object metadata), Functions (server-less compute on the edge), Push Notifications, and IoT messaging across 1B+ devices. The PubNub REST API runs… | thin | 2 |
| Liveblocks | Liveblocks is a real-time collaboration platform that provides ready-made building blocks for multiplayer experiences, including presence, broadcast events, shared storage (LiveObject/LiveList/LiveMap), comments and threads, notifications,… | strong | 1 |
| Azure Web PubSub | Azure Web PubSub is a fully-managed service that enables building real-time, two-way messaging applications using publish-subscribe patterns over WebSockets. It supports broadcasting messages to clients in groups, sending messages to speci… | developing | 1 |
| SuperViz | SuperViz provides real-time collaboration and data-synchronization infrastructure for web applications - presence, realtime data channels, video huddle/meetings, contextual comments, and mouse pointers. The product is SDK-first (@superviz/… | developing | 1 |
| Wazo | Wazo Communication Inc. builds the Wazo Platform, an open-source (GPL-3.0) programmable unified-communications and contact-centre platform assembled from Asterisk, Kamailio, RabbitMQ, PostgreSQL and nginx, which MSPs, carriers, telecom int… | thin | 25 |
| Agora | Agora is a real-time engagement platform providing ultra-low latency voice, video, signaling, chat, interactive whiteboard, cloud recording, real-time speech-to-text, and conversational AI infrastructure for human-to-human and human-to-AI… | thin | 11 |
| Massive (formerly Polygon.io) | Polygon (Polygon.io, rebranded as Massive in early 2026) provides real-time and historical market data APIs across US stocks, options, indices, forex, cryptocurrencies, and futures. Coverage is delivered through REST endpoints and WebSocke… | exemplar | 7 |
| Novu | Novu is the open-source notification infrastructure for developers. A single REST API and workflow engine route a triggered event across in-app inbox, email, SMS, push, chat (Slack / Discord / MS Teams / WhatsApp) and custom channels — wit… | exemplar | 1 |
| Kraken | Kraken is one of the world's largest and longest-running cryptocurrency exchanges, founded in 2011 and headquartered in San Francisco. Kraken offers Spot and Futures trading, staking and yield through Kraken Earn, NFT marketplace access, O… | exemplar | 24 |
| Gemini Trust Company | Gemini Trust Company, LLC is a United States cryptocurrency exchange and custodian, founded in 2014 and headquartered in New York, regulated as a New York State Department of Financial Services trust company. It operates the Gemini Exchang… | exemplar | 2 |
| Amazon API Gateway | Amazon API Gateway is a fully managed service that makes it easy to create, publish, maintain, monitor, and secure APIs at any scale. It acts as the front door for applications to access backend services, supporting REST APIs, HTTP APIs, a… | exemplar | 13 |
| Heroic Labs | Heroic Labs is the company behind Nakama, a leading open-source game backend server providing a comprehensive REST, WebSocket, and gRPC API for building scalable multiplayer and social games. The platform delivers essential backend service… | exemplar | 4 |
| Aedifion | aedifion GmbH is a Cologne-based PropTech founded in 2017 that operates a vendor-neutral, patented cloud platform for the optimized operation of non-residential buildings. The platform ingests real-time operating data from all building tra… | exemplar | 2 |
| Cumulocity | Cumulocity is an enterprise AIoT (Artificial Intelligence of Things) platform that connects, manages, and analyzes industrial assets from cloud to edge. Founded inside Software AG and divested via a 2025 management buyout into an independe… | strong | 17 |
| Dolby | Dolby Laboratories is an audio and video technology company whose developer platform, Dolby OptiView, is the merged surface of the original dolby.io platform, THEO Technologies (THEOplayer, THEOlive, THEOads) and Millicast. It ships public… | strong | 13 |
| Azure Service Bus | Azure Service Bus is a fully managed enterprise message broker with message queues and publish-subscribe topics, providing reliable message delivery for decoupling applications and services in cloud and hybrid environments. | strong | 1 |
| Red5 | Red5 provides real-time streaming infrastructure for live video and audio delivery at scale. The Red5 Pro platform includes a media server, Stream Manager 2.0 for autoscaling cloud deployments, the Brew Mixer for composite stream productio… | strong | 3 |
| SiftingIO | Cross-asset market data APIs covering US equities, forex, cryptocurrency, DeFi/on-chain, commodities, and SEC/EDGAR fundamentals, aggregated across venues and normalized into one JSON schema so every asset class shares the same fields, aut… | strong | 1 |
| MaiCoin | MaiCoin is a Taiwan-based digital asset group that operates MAX (MaiCoin Assets eXchange), a regulated cryptocurrency exchange offering spot trading, margin borrowing (m-wallet), staking, and fiat TWD on/off-ramps. MAX publishes a public V… | strong | 1 |
| AgentMail | AgentMail is an API-first email platform that gives AI agents their own email inboxes to autonomously send, receive, reply to, and act on email. Unlike traditional transactional email APIs built for one-way notifications, AgentMail is desi… | strong | 1 |
| ThingSpeak | ThingSpeak is an IoT analytics platform from MathWorks that lets devices aggregate, visualize, and analyze live data streams in the cloud. Devices push telemetry to channels via a REST update endpoint or the `mqtt3.thingspeak.com` MQTT bro… | strong | 2 |
| Odds API | OpenAPI-first sports betting odds API (odds-api.net) providing bookmaker odds, odds comparison, arbitrage, positive EV, line movement, and racing/sports coverage via REST plus SSE and WebSocket streaming. Agent-native with an MCP server, l… | strong | 1 |
| Amazon SNS | Amazon Simple Notification Service (SNS) is a fully managed messaging service for both application-to-application (A2A) and application-to-person (A2P) communication. It enables pub/sub, SMS, email, and mobile push notifications. | strong | 1 |
| Decart | Decart is an AI research lab and API platform building real-time world models — foundation models that generate and transform video frame-by-frame as they are watched. Its Decart API Platform (platform.decart.ai) exposes the Lucy family of… | strong | 2 |
| Lighter | Lighter is a decentralized perpetual futures exchange built on zkLighter, a zero-knowledge rollup that produces verifiable proofs of order matching and liquidations while targeting the latency of a centralized venue. Traders register a Lig… | developing | 1 |
| Qfex | QFEX is the first 24/7 exchange built exclusively for US equities, commodities, and FX, offering high-leverage perpetual futures on traditional assets without a broker. Founded by former Tower Research and Citadel engineers who met studyin… | developing | 1 |
| Binance.US | Binance.US (operated by BAM Trading Services, Inc.) is a U.S.-regulated digital asset marketplace offering spot trading, staking, OTC and custodial services across 100+ cryptocurrencies. Its public developer program exposes a signed REST A… | developing | 3 |