Tx Decoder
Paste a raw signed Bitcoin transaction — the hex a wallet asks you to export for air-gapped signing — and read exactly what it does before broadcasting: every input, every output, values in satoshi, script types, SegWit witness data, locktime. Parsed byte by byte from the serialized format, entirely offline.
This tool is plain client-side JavaScript — no accounts, no server calls, no telemetry, not even a web font from a CDN. To keep it forever: press Ctrl + S (Mac: Cmd + S), choose "Webpage, Complete", and open the saved file any time — with Wi-Fi off, in airplane mode, on a machine that never touches the internet.
Decode a raw transaction
Paste a raw signed Bitcoin transaction (the hex a wallet asks you to export for air-gapped signing) and read exactly what it does before broadcasting: every input, every output, values in satoshi, script types, SegWit witness data, locktime — parsed byte by byte from the serialized format, entirely offline. Try it on the genesis block's coinbase transaction, the raw hex every long-time bitcoiner keeps around.
How the Tx Decoder works
A raw Bitcoin transaction is a flat byte string, and every field in it is meaningful: the version, an optional SegWit marker-and-flag pair, the input count, each input's outpoint and unlocking script, the output count, each output's value in satoshi and locking script, and the locktime. The decoder walks that string byte by byte with proper variable-length integer parsing — the same discipline wallets use — and refuses anything that does not parse exactly, because a decoder that "fixes" malformed input would be lying to you.
For each input it identifies the script type from the unlocking data: P2PK (the original pay-to-pubkey), P2PKH, P2SH, or the SegWit family, where the proof lives in a separate witness structure and the on-chain script shrinks to a push of the witness program. For each output it reads the value in satoshi exactly — no floating point, ever — and decodes the destination script. The tool also computes a rough virtual-size estimate so you can sanity-check the fee your wallet attached against the current sat/vB rate.
What it will not do is broadcast, sign, or "improve" anything. This is a reader, not a sender: its job is to let you verify, before you commit, that the transaction pays who you think it pays, at the amount you expect, with a change address that belongs to your wallet. That habit — decode, read, then broadcast — is the strongest defense against clipboard malware and compromised co-signers alike. The genesis coinbase transaction included in the example is a good first run: 50 BTC, one input, no fees, and a small message from Satoshi in the script.
Tx Decoder — questions
Can this tool broadcast or modify a transaction? +
No. It is a pure reader: it parses hex locally and displays what the bytes say. It has no network access by design, cannot sign, and cannot broadcast. You stay in control of where (and whether) the transaction is ever submitted.
Which transaction types can it decode? +
The standard set: legacy P2PK, P2PKH and P2SH, SegWit v0 (P2WPKH and P2WSH) with witness data, and taproot (P2TR) key-path spends, plus OP_RETURN data outputs. Anything exotic will still parse at the byte level; scripts are shown as hex rather than interpreted.
Why decode a transaction at all if my wallet shows it? +
Because hardware wallets and air-gapped signers show you a summary, and summaries are exactly what malware tries to subvert. Decoding the raw hex yourself — on an offline machine — is the verification step that closes that gap: the bytes are the transaction, and the bytes do not lie.
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