Web3 in Flutter

One Flutter app, Flutter Counter, that proves Flutter can be a complete Web3 client. It does three things on every major chain family:

1. Reads blockchain data: balances, recent activity and counter values.

2. Authenticates users in three ways:

   • the app is the wallet;
   • it connects to wallets already installed on the device, without an SDK;
   • it connects through an SDK (Reown AppKit, and near_wallet_connect for NEAR).

   Users then sign in to a backend with a signed message.

3. Writes to the blockchain by calling a counter contract.

Chain family	Networks
EVM	Sepolia, Base Sepolia, Arbitrum Sepolia, OP Sepolia
Solana	devnet
Sui	testnet
Cosmos	Osmosis testnet (osmo-test-5)
NEAR	testnet

Testnets only. The keys in keys/ are public on purpose so that anyone can redeploy and test. Never send real funds to them.

How Wallets Connect

Whichever way a wallet connects, the rest of the app sees the same signer: an address that signs messages (for sign-in) and transactions (for writes).

	Android	iOS	Web	macOS, Windows, Linux
1. In-app wallet	every chain	every chain	every chain	every chain
2. Installed wallet, no SDK	Solana: Mobile Wallet Adapter, Phantom and Solflare deep links	Solana: Phantom and Solflare deep links	EVM (EIP-6963), Solana and Sui (Wallet Standard), Osmosis (Keplr, Leap)	none
2. Open the web version in a wallet's browser	MetaMask, Phantom, Solflare, Keplr	same	(not needed)	none
3. SDK	EVM and Solana (Reown AppKit), NEAR (Intear)	same	NEAR (Intear)	NEAR (Intear)

Gaps are real limits, not missing work: EVM, Sui and Cosmos wallet apps can only be reached from a native app through WalletConnect, and NEAR wallets have no SDK-free way in. The Sign in screen explains each one where it applies.

Reown needs a project ID. The one in flutter/lib/src/wallet/sdk/sdk_wallets.dart is public and only accepts this app's IDs (com.keepdeploying.flutter_counter, com.keepdeploying.flutterCounter). For your own app, create a project at dashboard.reown.com and allowlist your app's IDs there.

Repo Layout

Folder	What it holds
flutter/	The Flutter app
server/	Pure Dart backend: nonces, signature verifiers for every chain, sessions
contracts/	The counter contract for each chain, and deployments.json with every address
keys/	Public testnet keys: the dev recovery phrase and the Android debug keystore
scripts/	Publish the web app to GitHub Pages and the APK to GitHub Releases
tool/	setup_platforms.dart, sync_deployments.dart, and verify_signatures/ (checks our signatures with each chain's JS libraries)
DEPLOYS.md	Log of every contract deploy, web deploy and APK release

The repo commits only source code and the files that declare dependencies. Platform folders (flutter/android/, flutter/ios/, and so on), build output and downloaded dependencies are generated on your machine.

Prerequisites

• Flutter 3.47 or newer (Dart 3.13 or newer)
• For each platform you want to run, its usual Flutter setup (Android Studio, Xcode, Visual Studio, or the Linux desktop packages)
• On Linux: libsecret-1-dev to build, and a running keyring (GNOME Keyring or KWallet) to save the in-app wallet. Without a keyring, the wallet stays in memory until the app closes.

You only need the chain toolchains (Foundry, Anchor, Sui CLI, and so on) if you want to redeploy contracts. See contracts/README.md.

Run the App

git clone https://github.com/keepdeploying/web3-in-flutter.git
cd web3-in-flutter
flutter pub get
dart run tool/setup_platforms.dart
cd flutter
flutter run

tool/setup_platforms.dart runs flutter create for Android, iOS, web, macOS, Windows and Linux. It then applies the changes this app needs:

• the Android INTERNET permission, macOS network access and the shared signing key;
• what local_auth needs for fingerprint and Face ID unlock (a FlutterFragmentActivity, the USE_BIOMETRIC permission, an AppCompat launch theme and NSFaceIDUsageDescription);
• what wallets need: the fluttercounter:// link they answer on, the wallet apps the app may look for (Android <queries>, iOS LSApplicationQueriesSchemes), plain WebSockets to localhost for the Mobile Wallet Adapter, and Flutter's own deep linking turned off;
• a Gradle fix for a plugin Reown AppKit brings in (coinbase_wallet_sdk compiles against an old Android API and names a file it doesn't ship).

It is safe to run again, and worth re-running after pulling changes to it.

Run From Your IDE

• VS Code: open the repository's root folder and accept the recommended extensions. The Run and Debug view (Ctrl/Cmd + Shift + D) then lists the app (debug, profile, release, Chrome), the tests, the server, and "Server and Flutter" together. Opening the flutter folder on its own works too.
• Android Studio: open the repository's root folder. The run configurations in .idea/runConfigurations show up in the toolbar.

Run the Server

cd server
dart run bin/server.dart

The server listens on http://localhost:8080. By default, the app runs the same Dart code in-process, so you only need the server if you want to test the HTTP backend.

Tests

cd flutter && flutter test
cd server && dart test

Try It From the Command Line

The app's chain code is plain Dart, so these tools run it against the real testnets with the dev recovery phrase in keys/:

cd flutter
dart run tool/addresses.dart      # the dev wallet's address on every chain
dart run tool/live_reads.dart     # read every counter, through the RPC pools
dart run tool/try_writes.dart     # send increment, decrement and reset on every network
dart run tool/try_sign_in.dart    # sign in to a running server on every network and level
dart run tool/sign_vectors.dart   # signatures to check with tool/verify_signatures

try_writes.dart sends real transactions and spends a little test currency. Pass network IDs (sepolia, solana-devnet, sui-testnet...) to run only some.

Toolchain Versions Used

Tool	Version
Flutter / Dart	3.47.6 / 3.13.5
Foundry / Solidity	1.8.4 / 0.8.37
Anchor / Agave (Solana CLI)	1.2.0 / 4.3.0
Sui CLI	1.81.0
osmosisd	31.0.3
near-cli-rs / cargo-near	0.30.1 / 0.22.0
Rust	1.97 (host), 1.86 for CosmWasm, Solana platform tools for on-chain builds
binaryen (wasm-opt) / cosmwasm-check	133 / 2.2.10

Publish

Nothing publishes automatically. Run these by hand and record each run in DEPLOYS.md:

scripts/deploy-pages.sh   # builds the web app and pushes it to the gh-pages branch
scripts/release-apk.sh    # builds the APK and creates a GitHub Release (needs the gh CLI)