Flare

Your apps' backend, on Cloudflare. Like Firebase, but it's your own Worker: phones work offline, share data with each other, and catch up the moment they're back online.

Sync, auth, feature flags, push notifications, deep links, product analytics, crash reporting and a support chat, in one repo. Website: flare.jkyf.dev.

What you get

Offline first. Every phone keeps a full local copy in SQLite and writes instantly. Sync happens in the background.

Shared spaces. Phones join a space (a household, a team) with an 8‑letter invite code.

Merges that make sense. Two people edit at once and nothing gets lost: newest edit wins per field, lists keep their order, sets and counters merge. It's the approach Figma and Linear use for their data, not a text CRDT like Yjs (why).

iOS, Android and the web. One Rust core, with Swift and Kotlin on top. Web pages read and write through your Worker.

Server code that reacts. Say what should happen when a collection changes (start a job, file an item, send a push) and your Worker runs it after every change, from a phone, a web page or the server itself. Nothing is missed, and results sync back to every phone (triggers).

Feature flags. List them in one flags.json; Cloudflare Flagship serves them. Typed on every platform with no codegen step, and they work offline.

Deep links that survive an install. A shared link opens the app on the right screen, or a landing page and the store when it isn't installed. The link comes through the install too: by itself on Android, with one paste tap on iPhone. No Branch or AppsFlyer.

Analytics and crashes. A Rust SDK queues events on disk and sends them in batches to Iceberg tables you query with SQL. Crashes, hangs and errors arrive the same way, with their stack and the last 30 events before them, from MetricKit on iOS and the platform's own crash records on Android. No Firebase, no Sentry, no extra SDK.

Support chat. A chat bubble for your site with email both ways, one inbox for all your apps, and Claude to answer from. No Intercom.

Cheap to run. One Durable Object per space, photos in R2. It sleeps until someone syncs. Nothing to babysit.

Add it

Worker

pnpm add "@sync/server@github:johnkueh/flare#0.7.0&path:/server"
pnpm add "@flare/auth@github:johnkueh/flare#0.7.0&path:/auth"   # accounts (AUTH.md)
pnpm add "@flare/flags@github:johnkueh/flare#0.7.0&path:/flags" # feature flags (FLAGS.md)
pnpm add "@flare/push@github:johnkueh/flare#0.7.0&path:/push"   # push notifications (PUSH.md)
pnpm add "@flare/links@github:johnkueh/flare#0.7.0&path:/links" # deep links (LINKS.md); then npx flare-links setup

export { SpaceObject } from "@sync/server/space";

iOS: add the package https://github.com/johnkueh/flare and link SyncKit and SyncClient.

Android

// settings.gradle.kts
maven("https://jitpack.io")
maven("https://pub-796846793f3e431ab3a92e0577c57dde.r2.dev/maven")

// app/build.gradle.kts
implementation("com.github.johnkueh:flare:0.7.0")

Then describe your data in one JSON file and open the store:

let store = try SyncStore.open(path: dbPath, schemaJson: schema)
try store.putDoc(collection: "groceries", doc: id, fieldsJson: #"{"name":"Milk"}"#)

Learn more

• SYNC.md: setup in full, the data model, web pages, releasing
• PROTOCOL.md: the wire format, for anyone writing a client
• AUTH.md: accounts on Better Auth, signing in from a phone
• FLAGS.md: feature flags on Cloudflare Flagship, for iOS, Android, web, Node and Rust
• PUSH.md: push notifications to APNs and FCM from your Worker, and asking for permission gracefully
• LINKS.md: deep links that open the app, and survive an install, served by your Worker
• SUPPORT.md: a support chat widget and inbox, with email both ways, that you run from Claude
• TELEMETRY.md: product analytics and crash reporting into Cloudflare Basin, from a Rust SDK