Now in TestFlight beta on Solana devnet

A native iOS signer for Solana Squads multisigs.

Cosign lets you review and co-sign Squads v4 proposals from your phone, with your keys held on device. Every proposal is decoded and inspectable before you approve, so you always know exactly what you are signing.

Coming soon How it works

What Cosign does

Built for the way multisig signing actually works.

Self-custody by default

You hold your own keys. Cosign cannot move funds or sign on your behalf. Approvals happen only on your device.

Squads v4 co-signing

Review pending proposals, see who has approved, and add your signature toward the threshold, all from your phone.

Hardware signers

Connect a Ledger over Bluetooth or a YubiKey over NFC or USB, with on-device address confirmation before you sign.

Relay-only, verifiable

The relay is a thin client that proxies Solana RPC and helps decode proposals. No custody, no key access, nothing to trust blindly.

Native iOS

Built in SwiftUI with Dynamic Type, dark mode, and Face ID. It feels like a real iPhone app because it is one.

Decoded, inspectable proposals

Every instruction is decoded into plain language, with severity and confidence, so you know exactly what a proposal does before approving.

Security model

Your keys stay on your device.

Signing keys are generated and stored on your iPhone, in the iOS Keychain or on your hardware signer. They never leave the device. The Cosign relay is a thin, verifiable client that proxies Solana RPC and helps decode proposals. It cannot move funds and never holds your keys.

Keys on device

Held in the iOS Keychain or your Ledger or YubiKey.

Thin verifiable relay

Proxies RPC and decodes proposals. It cannot sign or move funds.

Beta

Try Cosign on devnet.

The beta runs on Solana devnet, so you can connect signers, build proposals, and co-sign without using real funds. We would love your feedback while we work toward mainnet.

Coming soon

Devnet only. No real funds are at risk.