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Multisig Transaction Builder & Decoder

Build a Safe-compatible batch JSON, or decode a MultiSend blob into its individual calls.

Call #1

Download Safe batch JSON

Import this file directly in your Safe: Apps → Transaction Builder → Upload batch.

Two directions, one format

Safe’s Transaction Builder app has its own JSON import format for batching calls, and its MultiSend contract has its own binary packing format for executing them together on-chain. This tool builds the former and decodes the latter — useful whether you’re assembling a batch to propose, or checking exactly what an existing batch transaction actually does.

How it works

Building generates the exact JSON shape Safe’s own Transaction Builder expects, ready to import with no retyping. Decoding parses the MultiSend packing format directly — operation type, target address, value, and calldata length prefix for each sub-call — entirely in your browser.

Frequently asked questions

In your Safe: open the Transaction Builder app (under Apps), choose "Upload batch", and select the downloaded file — it loads every call from the batch ready to review and propose, exactly as if you'd added them one by one in the UI.

Safe batches multiple calls into one on-chain transaction by routing them through a MultiSend contract, which packs every sub-call's operation type, target, value, and calldata together into one bytes blob. Decoding it recovers each individual call — useful for checking exactly what a batch transaction actually does before signing it.

No — this only builds a JSON file (for building) or reads bytes you paste in (for decoding). Nothing here connects a wallet, proposes a transaction, or touches your Safe directly.

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