Lark - Magical Multiplayer Data
Yeah, Lark Does That
Web Apps
Use LarkJS with Vanilla Javascript, React, or your favorite framework. Sync any JSON data you want, and add in presence and volatile data (great for typing indicators or cursor movement) using the same SDK.
Mobile Apps
Use Firebase Mobile SDKs for Flutter, React Native, Expo, and more to get up and running quickly with a Lark-powered mobile application using the SDKs you already love.
AI-Native Apps
Lark makes it easy to build the next generation of apps using AI. Your agent can provision databases, update security rules, and inspect data directly using our Lark Skill and CLI tool.
Works with everything you already use
JavaScript
TypeScript
React
Node.js
Swift
Kotlin
iOS
Android
Unity
Flutter
C#
{}<br>REST API
Own Your Stack
We believe that every developer should be able to own their backend. Lark is proudly open-source under an AGPL license, allowing you to use it in commercial projects with no limits. Don't want to deal with devops? Let us host it. Either way, your data and your code stay yours.
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Permissive Licensing
The entire server is on GitHub under the AGPL license which means you can use it for your next weekend hack or your major commercial day-job.
Read it, fork it, audit it, ship patches. The stack that runs our cloud is the same code you can run yourself.
Easy to start
Clone the repo and make up brings up the whole stack locally so you can take it for a test drive.
Going to production? Our Fly.io quickstart stands up a real, TLS-terminated deployment in a few minutes.
∞
Switch anytime
Lark Cloud is powered by the same server in the open-source repo.
Start on Cloud and move in-house later, or start self-hosted and hand us the ops when you scale.
Firebase 🔜 Lark
Firebase Realtime Database was magical when it launched. Lark keeps everything you love about that API and gives you full control. Use the same client SDKs and skip the major rewrite while getting a fast, modern engine powering your data.
The API you already know
Just change firebaseio.com to larkdb.net in your Firebase config. You're done.
Lark can be used as a drop-in replacement for Firebase RTDB in your existing apps. Use the official Firebase SDKs (Web, Mobile, REST). Keep your auth, keep your code, get a better engine.
Features for the modern dev
Firebase was built for 2012. Lark is built for 2026.
Volatile Data: Fire-and-forget updates. Perfect for real-time game data or cursor presence, powered by WebTransport in the browser.
First-Class AI Support: Lark excels at letting your AI coding assistant handle the nitty gritty without making you navigate a labyrinth just to setup your project.
Yours to run
With Firebase, there's exactly one place your data can live. With Lark, it's your call.
Self-host the open-source server for free, or run on Lark Cloud at half of Firebase's rates, and move between the two whenever you want.
Either way, the same drop-in API and you're in control.
Your Place or Ours
Run the open-source version on your own infrastructure, or let us handle the devops so you can focus on building your app.
Open Source
Own your whole stack.
Free
✓ AGPL-licensed
✓ Self-host on your own hardware
✓ No limits, no seats
✓ Firebase drop-in compatibility
✓ Community support
View on GitHub
Most popular<br>Cloud
We run it. You ship.
$10<br>/month
✓ Includes 2 GB storage + 20 GB bandwidth
✓ Then $2.50/GB storage, $0.50/GB bandwidth (egress)
✓ Volatile bandwidth billed at 1/5th the rate
✓ Scales as high as you need
✓ Switch from Firebase and save money today
✓ 14-day free trial
Start Free Trial
Enterprise
For serious scale.
Let's talk
✓ For those running 10k+ Peak CCU
✓ Enterprise SLA
✓ Hands-on onboarding & migration help
✓ Priority support on Cloud with an SLA
✓ Enterprise support contracts for on-prem
Contact Us
Full breakdown and pricing FAQ on the pricing page.