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Alternatives · Realtime

Yjs alternatives (2026)

Yjs: The MIT CRDT. Pair with Liveblocks for hosted rooms; this is the library, not the meter.

Its Catch: Not a product. No hosted SKU, no pricing page, no support SLA.

Below: 8 free or free-tier tools from the same category (realtime and WebSocket tools), free and open source first, then the closest match by shared tags. Each keeps its own Catch.

  1. 1.Socket.IOMIT realtime library with fallbacks, not a hosted product

    Free / OSS · OSS/MIT · 63.2k GitHub stars

    VerdictThe MIT socket library. Free as in you run it.

    CatchYou bring the host. Horizontal scale needs Redis (or equivalent) adapter. This is not LiveKit and not a managed pub-sub. CORS, sticky sessions, and polling surprises remain your bugs.

  2. 2.Pion WebRTCMIT embeddable Go WebRTC library — not a rooms product

    Free / OSS · OSS/MIT · 16.9k GitHub stars

    VerdictMIT Go WebRTC library. Free to embed; not a rooms stack.

    CatchEmbeddable Go library — not LiveKit rooms product, not mediasoup C++/Node media server, not PeerJS browser-only P2P helper. You assemble signaling and any SFU-class topology yourself. Distinct from LiveKit, mediasoup, and PeerJS.

  3. 3.matrix-js-sdkApache-2.0 Matrix client library — needs a homeserver

    Free / OSS · Apache-2.0 · 2.2k GitHub stars

    VerdictApache-2.0 Matrix client. Free library; bring a homeserver.

    CatchClient lib only — you need a homeserver (Tuwunel etc.). Not a homeserver and not a generic WS product. Distinct from Tuwunel.

  4. 4.LiveKitApache-2.0 realtime rooms, SFU, and agents

    Free / OSS · Apache-2.0 · 21.6k GitHub stars

    VerdictApache-2.0 voice/video/agent runtime. Self-host is the free path; Cloud pricing is not confirmed here.

    CatchSelf-hosting an SFU is ops-heavy. Cloud Build pricing and free allowances are not confirmed here; check the vendor site. Do not assume Cloud is free.

  5. 5.CentrifugoApache-2.0 Go realtime server binary, not in-process Socket.IO

    Free / OSS · Apache-2.0 · 10.9k GitHub stars

    VerdictApache-2.0 realtime binary. Free as in you operate the server.

    CatchYou run it. This is not Socket.IO in-process. Cloud/PRO pricing is not confirmed here — no invented Cloud prices. Ops, clustering, and Redis when you scale stay yours.

  6. 6.MercureAGPL-3.0 SSE hub; homepage still says MIT

    Free / OSS · AGPL-3.0 · 5.3k GitHub stars

    VerdictAGPL SSE hub. Believe the LICENSE file, not the MIT line on the homepage.

    CatchHomepage still says the Hub is MIT-licensed. The LICENSE file is AGPL-3.0 — print the file. SSE, not WebSockets, not Pusher protocol. Distinct from Socket.IO and Soketi. Cloud/Enterprise exist; check their pricing page. OSS self-host is the free path.

  7. 7.NATSApache-2.0 subject-based messaging and streaming fabric

    Free / OSS · Apache-2.0 · 20.9k GitHub stars

    VerdictApache-2.0 messaging fabric. Free as in you run the server. Not Socket.IO.

    CatchSubject-based messaging/streaming fabric — not an in-process WS lib and not a Go realtime binary alone. Distinct from Socket.IO and Centrifugo.

  8. 8.AnyCableMIT realtime for Action Cable with delivery guarantees

    Free / OSS · Freemium · 2.4k GitHub stars

    VerdictMIT Action Cable path. OSS tier is free; not Soketi, not Socket.IO.

    CatchDelivery guarantees + presence + Action Cable / multi-backend — not a Pusher-protocol server. Distinct from Socket.IO and Centrifugo. Pro and Managed exist; prices not reprinted here.

FAQ

What are the best free alternatives to Yjs?
Socket.IO, Pion WebRTC, matrix-js-sdk, LiveKit, Centrifugo. All are reviewed on Stack Gems in the same category (realtime and WebSocket tools); 8 free or open source.
What is the catch with Yjs?
Not a product. No hosted SKU, no pricing page, no support SLA.
Is there an open-source alternative to Yjs?
Yes: Socket.IO (OSS/MIT), Pion WebRTC (OSS/MIT), matrix-js-sdk (Apache-2.0), LiveKit (Apache-2.0).

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