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-images.s3.amazonaws.com/shared/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
  - url: graphql/realtime-graphql.md
    type: GraphQL
- 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
- 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/
- 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
- 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: DomainSecurity
  url: security/realtime-domain-security.yml
- 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: JSONLDContext
  url: json-ld/realtime-context.jsonld
- type: Vocabulary
  url: vocabulary/realtime-vocabulary.yml
- type: Examples
  url: examples/
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com