Realtime

aid: realtime
name: Realtime
description: 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).
image: https://kinlane-productions2.s3.amazonaws.com/apis-json/apis-json-logo.jpg
url: https://github.com/api-evangelist/realtime
created: '2026-05-22'
modified: '2026-05-22'
specificationVersion: '0.19'
type: Index
tags:
  - Realtime
  - WebSocket
  - WebRTC
  - Server-Sent Events
  - MQTT
  - Push Notifications
  - Pub Sub
  - Presence
  - Signaling
  - Topic
apis:
  - aid: realtime:websocket
    name: WebSocket
    description: 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 for chat, multiplayer, live dashboards, collaboration, and as the carrier for higher-level realtime SDKs from Ably, Pusher, PubNub, Phoenix Channels, Socket.IO, and others.
    humanURL: https://datatracker.ietf.org/doc/html/rfc6455
    baseURL: wss://
    tags:
      - WebSocket
      - Protocol
      - Bidirectional
      - Standard
    properties:
      - type: Specification
        url: https://datatracker.ietf.org/doc/html/rfc6455
      - type: Documentation
        url: https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API
      - type: ClientAPI
        url: https://websockets.spec.whatwg.org/

  - aid: realtime:server-sent-events
    name: Server-Sent Events (SSE)
    description: 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 as the carrier for LLM token streams from OpenAI, Anthropic, and other AI APIs.
    humanURL: https://html.spec.whatwg.org/multipage/server-sent-events.html
    baseURL: https://
    tags:
      - SSE
      - Server-Sent Events
      - Protocol
      - Unidirectional
      - Standard
    properties:
      - type: Specification
        url: https://html.spec.whatwg.org/multipage/server-sent-events.html
      - type: Documentation
        url: https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events

  - aid: realtime:webrtc
    name: WebRTC
    description: 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 SCTP-based data channels. It powers video conferencing (LiveKit, Daily, Agora, Twilio Video, Zoom Web), live audio rooms, and low-latency game streaming.
    humanURL: https://webrtc.org/
    tags:
      - WebRTC
      - Peer-to-Peer
      - Video
      - Audio
      - Data Channel
      - Protocol
      - Standard
    properties:
      - type: Specification
        url: https://www.w3.org/TR/webrtc/
      - type: Documentation
        url: https://developer.mozilla.org/en-US/docs/Web/API/WebRTC_API
      - type: Portal
        url: https://webrtc.org/

  - aid: realtime:mqtt
    name: MQTT
    description: 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, and Mosquitto. MQTT v5 adds shared subscriptions, message expiry, reason codes, and topic aliases.
    humanURL: https://mqtt.org/
    tags:
      - MQTT
      - IoT
      - Pub Sub
      - Protocol
      - Standard
    properties:
      - type: Specification
        url: https://docs.oasis-open.org/mqtt/mqtt/v5.0/mqtt-v5.0.html
      - type: Portal
        url: https://mqtt.org/

  - aid: realtime:coap
    name: CoAP
    description: 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 LPWAN deployments where MQTT's TCP overhead is undesirable.
    humanURL: https://datatracker.ietf.org/doc/html/rfc7252
    tags:
      - CoAP
      - IoT
      - Constrained Devices
      - Protocol
      - Standard
    properties:
      - type: Specification
        url: https://datatracker.ietf.org/doc/html/rfc7252
      - type: Specification
        url: https://datatracker.ietf.org/doc/html/rfc7641

  - aid: realtime:grpc-streaming
    name: gRPC Streaming
    description: 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 bridging to browsers and Connect protocol providing buf.build's HTTP/JSON-friendly alternative.
    humanURL: https://grpc.io/docs/what-is-grpc/core-concepts/
    tags:
      - gRPC
      - Streaming
      - Bidirectional
      - HTTP/2
      - Protocol
    properties:
      - type: Documentation
        url: https://grpc.io/docs/what-is-grpc/core-concepts/
      - type: Specification
        url: https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md

  - aid: realtime:graphql-subscriptions
    name: GraphQL Subscriptions
    description: 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 Apollo, Hasura, AWS AppSync, and most production GraphQL servers.
    humanURL: https://spec.graphql.org/October2021/#sec-Subscription
    tags:
      - GraphQL
      - Subscriptions
      - Realtime
      - WebSocket
    properties:
      - type: Specification
        url: https://spec.graphql.org/October2021/#sec-Subscription
      - type: Documentation
        url: https://the-guild.dev/graphql/ws

  - aid: realtime:webtransport
    name: WebTransport
    description: 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-based browsers and progressively adopted in production.
    humanURL: https://www.w3.org/TR/webtransport/
    tags:
      - WebTransport
      - HTTP/3
      - QUIC
      - Browser
      - Standard
    properties:
      - type: Specification
        url: https://www.w3.org/TR/webtransport/
      - type: Documentation
        url: https://developer.mozilla.org/en-US/docs/Web/API/WebTransport_API

  # Hosted realtime providers
  - aid: realtime:ably
    name: Ably
    description: 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 framing "Low-level APIs to build any realtime experience" for the Pub/Sub product.
    humanURL: https://ably.com/
    tags:
      - Realtime
      - Pub Sub
      - Channels
      - Chat
      - Provider
    properties:
      - type: Portal
        url: https://ably.com/
      - type: Documentation
        url: https://ably.com/docs
      - type: APIReference
        url: https://ably.com/docs/api
      - type: Pricing
        url: https://ably.com/pricing
      - type: Blog
        url: https://ably.com/blog
      - type: GitHubOrganization
        url: https://github.com/ably
      - type: StatusPage
        url: https://status.ably.com/

  - aid: realtime:pubnub
    name: PubNub
    description: 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 delivered anywhere in less than 30 ms" as its latency guarantee.
    humanURL: https://www.pubnub.com/
    tags:
      - Realtime
      - Pub Sub
      - Presence
      - Chat
      - Provider
    properties:
      - type: Portal
        url: https://www.pubnub.com/
      - type: Documentation
        url: https://www.pubnub.com/docs/
      - type: Pricing
        url: https://www.pubnub.com/pricing/
      - type: Blog
        url: https://www.pubnub.com/blog/
      - type: GitHubOrganization
        url: https://github.com/pubnub
      - type: StatusPage
        url: https://status.pubnub.com/

  - aid: realtime:pusher
    name: Pusher
    description: 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 proprietary WebSocket protocol with broad SDK coverage.
    humanURL: https://pusher.com/
    tags:
      - Realtime
      - Pub Sub
      - Channels
      - Push Notifications
      - Provider
    properties:
      - type: Portal
        url: https://pusher.com/
      - type: Documentation
        url: https://pusher.com/docs/
      - type: Pricing
        url: https://pusher.com/channels/pricing
      - type: GitHubOrganization
        url: https://github.com/pusher
      - type: StatusPage
        url: https://status.pusher.com/

  - aid: realtime:livekit
    name: LiveKit
    description: 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 JavaScript, Swift, Android, and Flutter. Available self-hosted or as LiveKit Cloud.
    humanURL: https://livekit.io/
    tags:
      - WebRTC
      - Video
      - Voice
      - AI Agents
      - Provider
      - Open Source
    properties:
      - type: Portal
        url: https://livekit.io/
      - type: Documentation
        url: https://docs.livekit.io/home/
      - type: GitHubOrganization
        url: https://github.com/livekit
      - type: Pricing
        url: https://livekit.io/pricing

  - aid: realtime:daily
    name: Daily
    description: 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-neutral open source orchestration framework for realtime voice and multimodal AI agents."
    humanURL: https://www.daily.co/
    tags:
      - WebRTC
      - Video
      - AI Agents
      - Provider
    properties:
      - type: Portal
        url: https://www.daily.co/
      - type: Documentation
        url: https://docs.daily.co/
      - type: APIReference
        url: https://docs.daily.co/reference
      - type: Pricing
        url: https://www.daily.co/pricing
      - type: GitHubOrganization
        url: https://github.com/daily-co

  - aid: realtime:agora
    name: Agora.io
    description: 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 the conversational intelligence of leading LLMs." Agora runs a global Software Defined Real-Time Network (SD-RTN).
    humanURL: https://www.agora.io/
    tags:
      - Realtime
      - Video
      - Voice
      - Signaling
      - Provider
    properties:
      - type: Portal
        url: https://www.agora.io/
      - type: Documentation
        url: https://docs.agora.io/en/
      - type: Pricing
        url: https://www.agora.io/en/pricing/
      - type: GitHubOrganization
        url: https://github.com/AgoraIO
      - type: StatusPage
        url: https://status.agora.io/

  - aid: realtime:twilio-video
    name: Twilio Video / Live
    description: 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 tokens, and Programmable APIs.
    humanURL: https://www.twilio.com/video
    tags:
      - WebRTC
      - Video
      - Live Streaming
      - Provider
    properties:
      - type: Portal
        url: https://www.twilio.com/video
      - type: Documentation
        url: https://www.twilio.com/docs/video
      - type: APIReference
        url: https://www.twilio.com/docs/video/api
      - type: GitHubOrganization
        url: https://github.com/twilio

  - aid: realtime:vonage-video
    name: Vonage Video API
    description: 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.
    humanURL: https://www.vonage.com/communications-apis/video/
    tags:
      - WebRTC
      - Video
      - OpenTok
      - Provider
    properties:
      - type: Portal
        url: https://www.vonage.com/communications-apis/video/
      - type: Documentation
        url: https://developer.vonage.com/en/video/overview
      - type: GitHubOrganization
        url: https://github.com/Vonage

  - aid: realtime:amazon-ivs
    name: Amazon Interactive Video Service (IVS)
    description: 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 service alongside the video stream.
    humanURL: https://aws.amazon.com/ivs/
    tags:
      - WebRTC
      - Video
      - Live Streaming
      - AWS
      - Provider
    properties:
      - type: Portal
        url: https://aws.amazon.com/ivs/
      - type: Documentation
        url: https://docs.aws.amazon.com/ivs/
      - type: Pricing
        url: https://aws.amazon.com/ivs/pricing/

  - aid: realtime:cloudflare-realtime
    name: Cloudflare Realtime
    description: 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/TLS — running on Cloudflare's global edge network.
    humanURL: https://developers.cloudflare.com/realtime/
    tags:
      - WebRTC
      - SFU
      - TURN
      - Edge
      - Provider
    properties:
      - type: Portal
        url: https://developers.cloudflare.com/realtime/
      - type: Documentation
        url: https://developers.cloudflare.com/realtime/
      - type: Pricing
        url: https://www.cloudflare.com/plans/

  # Open-source realtime frameworks
  - aid: realtime:socket-io
    name: Socket.IO
    description: 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 fallback). Powers chat, dashboards, and collaboration in thousands of production apps.
    humanURL: https://socket.io/
    tags:
      - WebSocket
      - Open Source
      - Framework
      - Node.js
    properties:
      - type: Portal
        url: https://socket.io/
      - type: Documentation
        url: https://socket.io/docs/v4/
      - type: GitHubOrganization
        url: https://github.com/socketio

  - aid: realtime:phoenix-channels
    name: Phoenix Channels
    description: 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 implements CRDT-based distributed presence tracking.
    humanURL: https://hexdocs.pm/phoenix/channels.html
    tags:
      - Elixir
      - Phoenix
      - WebSocket
      - Channels
      - Open Source
    properties:
      - type: Portal
        url: https://www.phoenixframework.org/
      - type: Documentation
        url: https://hexdocs.pm/phoenix/channels.html
      - type: GitHubOrganization
        url: https://github.com/phoenixframework

  - aid: realtime:centrifugo
    name: Centrifugo
    description: 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 fanout from application backends.
    humanURL: https://centrifugal.dev/
    tags:
      - WebSocket
      - Pub Sub
      - Open Source
      - Realtime Server
    properties:
      - type: Portal
        url: https://centrifugal.dev/
      - type: Documentation
        url: https://centrifugal.dev/docs/getting-started/introduction
      - type: GitHubOrganization
        url: https://github.com/centrifugal

  # Push notification systems
  - aid: realtime:onesignal
    name: OneSignal
    description: 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 APIs, SDKs, and a hosted console.
    humanURL: https://onesignal.com/
    tags:
      - Push Notifications
      - Mobile
      - Web Push
      - Provider
    properties:
      - type: Portal
        url: https://onesignal.com/
      - type: Documentation
        url: https://documentation.onesignal.com/
      - type: APIReference
        url: https://documentation.onesignal.com/reference
      - type: Pricing
        url: https://onesignal.com/pricing
      - type: GitHubOrganization
        url: https://github.com/OneSignal

  - aid: realtime:firebase-cloud-messaging
    name: Firebase Cloud Messaging (FCM)
    description: 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 browsers) for FCM-to-device delivery.
    humanURL: https://firebase.google.com/products/cloud-messaging
    tags:
      - Push Notifications
      - Mobile
      - Google
      - Provider
    properties:
      - type: Portal
        url: https://firebase.google.com/products/cloud-messaging
      - type: Documentation
        url: https://firebase.google.com/docs/cloud-messaging
      - type: APIReference
        url: https://firebase.google.com/docs/reference/fcm/rest

  - aid: realtime:apple-push-notification-service
    name: Apple Push Notification Service (APNs)
    description: 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 connection for Apple-to-device delivery.
    humanURL: https://developer.apple.com/documentation/usernotifications
    tags:
      - Push Notifications
      - Apple
      - iOS
      - HTTP/2
      - Provider
    properties:
      - type: Portal
        url: https://developer.apple.com/documentation/usernotifications
      - type: Documentation
        url: https://developer.apple.com/documentation/usernotifications/sending-notification-requests-to-apns

  - aid: realtime:web-push
    name: Web Push API
    description: 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 vendor push services (Mozilla autopush, Apple Push, FCM Web Push).
    humanURL: https://www.w3.org/TR/push-api/
    tags:
      - Push Notifications
      - Web
      - Standard
      - Browser
    properties:
      - type: Specification
        url: https://www.w3.org/TR/push-api/
      - type: Specification
        url: https://datatracker.ietf.org/doc/html/rfc8030
      - type: Specification
        url: https://datatracker.ietf.org/doc/html/rfc8291

  - aid: realtime:pushwoosh
    name: Pushwoosh
    description: 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.
    humanURL: https://www.pushwoosh.com/
    tags:
      - Push Notifications
      - Customer Engagement
      - Provider
    properties:
      - type: Portal
        url: https://www.pushwoosh.com/
      - type: Documentation
        url: https://docs.pushwoosh.com/
      - type: GitHubOrganization
        url: https://github.com/Pushwoosh

common:
  - type: Portal
    url: https://github.com/api-evangelist/realtime
  - type: GitHub
    url: https://github.com/api-evangelist/realtime
  - type: JSONSchema
    url: json-schema/realtime-channel.json
  - type: JSONSchema
    url: json-schema/realtime-message-envelope.json
  - type: JSONSchema
    url: json-schema/realtime-subscription.json
  - type: JSONSchema
    url: json-schema/realtime-presence.json
  - type: JSON-LD Context
    url: json-ld/realtime-context.jsonld
  - type: Vocabulary
    url: vocabulary/realtime-vocabulary.yml
  - type: Examples
    url: examples/

maintainers:
  - FN: Kin Lane
    email: [email protected]