op-txverify

op-txverify verifies Safe transactions, as a command-line utility and as a page at op-txverify.optimism.io. It helps users validate Safe multisig transactions by:

1. Parsing and presenting transactions in a clearly understandable manner
2. Identifying common addresses and contracts that users interact with
3. Verifying a transaction on a phone, independently of the computer being signed from
4. Simplifying access by allowing users to input transactions via QR codes

Verifying on a phone

The page at op-txverify.optimism.io shows the two EIP-712 hashes a hardware wallet displays, plus the decoded calldata, without involving the computer running the Safe UI. That matters because op-txverify on the signing computer proves nothing if that computer is compromised — it would report whatever the attacker wants.

1. Open the page on a phone, ideally on cellular rather than the same network as the computer.
2. Enter either the safeTxHash, or the Safe address, nonce, and network. Prefer the latter: those three values come from your own knowledge of the transaction, whereas a safeTxHash is usually handed over by the computer being distrusted. The entries are remembered for next time.
3. Compare the domain hash and message hash to your device, and the decoded call to what was actually approved.

Two properties are worth understanding:

• The hashes come from the Safe contract, read with encodeTransactionData over an RPC, not from the page's own arithmetic. The WebAssembly module recomputes them independently, so an RPC returning a wrong preimage shows up as a visible mismatch.
• The decode is core/parsing.go compiled to WebAssembly, so there is one decoder implementation rather than a JavaScript reimplementation that could drift from the CLI.

Supported chains are Ethereum, OP Mainnet, Base, and Sepolia. Safe 1.5.0 and later removed encodeTransactionData, so the page refuses those rather than failing obscurely.

The page prints a build commit and WebAssembly digest at the bottom. That is a version indicator, not an integrity check — serve-time HTML injection never touches the artifact the digest describes, so a matching digest does not prove the page you loaded is the page that was built. To confirm the hashes without trusting the page at all, read encodeTransactionData yourself on a block explorer's Read as Proxy tab, using the parameters the page displays.

QR code scanning

The QR scanning functionality provided by op-txverify allows you to verify Safe transactions by scanning QR codes displayed on a web interface. This is especially useful for air-gapped verification where transmitting data to the verification device over bluetooth or USB is not desirable.

To use the QR code scanner:

1. Open https://op-txverify.optimism.io on your mobile device.
2. Paste the transaction hash or Safe UI link of the Safe transaction you want to verify.
3. Run the following command on your verification device:

   op-txverify qr

4. A browser window will automatically open with the QR scanner interface. It is served on loopback only, so no other host on the network can submit a scanner result.
5. Display the QR codes on your mobile device to the QR scanner.
6. After successful scanning, op-txverify will verify the transaction and display the results.

Installation

op-txverify is not distributed as a release binary. Build the latest version from source before each signing ceremony.

Prerequisites:

• Go 1.23 or later
• Git

Install the latest main directly:

go install github.com/ethereum-optimism/op-txverify/cmd/op-txverify@main

Make sure your Go binary directory is on your PATH. For most local Go installations, this is:

export PATH="$(go env GOPATH)/bin:$PATH"

Or clone and build explicitly:

1. Clone the repository:

   git clone https://github.com/ethereum-optimism/op-txverify.git
   cd op-txverify

2. Build the binary:

   go build -trimpath -o ./bin/op-txverify ./cmd/op-txverify

3. Install it somewhere on your PATH:

   sudo mv ./bin/op-txverify /usr/local/bin/op-txverify

Confirm the installed binary:

op-txverify --version