Cardano Transaction Decoder

A CLI tool for decoding and comparing Cardano transactions. Turns raw CBOR hex into readable JSON so you can see exactly what's inside.

Who Is This For?

• dApp developers debugging failed transactions
• Smart contract builders comparing expected vs actual witness sets
• Teams migrating between transaction builder libraries
• Anyone who's seen "script integrity hash mismatch" and wanted to know why

What Problems Does It Solve?

• "Why won't my transaction validate?" — See the exact script data hash, redeemers, and datums
• "Two tx builders give different results" — Compare them side-by-side and find the exact field that differs
• "What's actually in this transaction?" — Decode any tx hex to readable JSON

Installation

npm install -g cardano-tx-decoder

Or use directly with npx:

npx cardano-tx-decoder decode 84a500...

CLI Usage

Decode a Transaction

# Full decode with pretty output
ctd decode 84a500d9010282825820...

# Decode from a file (for large transactions that exceed CLI limits)
ctd decode ./tx1.hex
ctd decode C:/path/to/transaction.txt

# Output as JSON
ctd decode ./tx.hex --json

Compare Two Transactions

Find exactly what differs between two transaction builds:

# Using file paths (recommended for large txs)
ctd compare ./tx1.hex ./tx2.hex

# Using direct hex
ctd compare <tx1-hex> <tx2-hex>

File Input

Any argument can be a file path instead of raw hex. This bypasses shell argument length limits (typically 128KB-2MB) for large transactions.

Files should contain raw hex (no 0x prefix), whitespace is automatically trimmed.

Example Output

================================================================================
TRANSACTION COMPARISON
================================================================================

--- TRANSACTION 1 ---
Script Data Hash: f952539efbf6ad2ff8bf380ef60a8f84c6473d1fcb7bb097f1f3dbb254d2b825
Inputs: 2
Outputs: 3
...

--- DIFFERENCES ---

❌ Script Data Hash DIFFERS
   TX1: f952539efbf6ad2ff8bf380ef60a8f84c6473d1fcb7bb097f1f3dbb254d2b825
   TX2: 5e4edebba50f3bf7be0d7ff7e07619b63d4edea30be0de8f641e5561206ef921
✅ Input ordering matches
❌ Witness set differences:
   Plutus data at index 0 differs
     Value differs at .fields[1]:
       TX1: 0x5139e81456c1b4e2f0af22c1e94ff22ea648588b03a7c7914b6eb256
       TX2: 0xc8d25b5c76b19bda9c88a0120a2dbcdc2ddd3f82921aa98ca3585428

Decode Plutus Data

Decode a datum or redeemer to readable JSON:

ctd decode-datum d8799f9fd8799fd8799f...

Decode Witness Set Only

ctd decode-witness a10281...

Library Usage

import { 
  decodeTransaction, 
  decodeWitnessSet,
  compareTransactions,
  decodePlutusData 
} from 'cardano-tx-decoder';

// Decode a transaction
const tx = decodeTransaction(txHex);
console.log(tx.scriptDataHash);
console.log(tx.witnessSet.plutusData);

// Compare two transactions
const comparison = compareTransactions(tx1, tx2);
if (!comparison.scriptDataHashMatch) {
  console.log('Script data hash differs!');
  console.log(comparison.witnessSetDifferences);
}

// Decode a datum to JSON
const datum = decodePlutusData(datumHex);
console.log(JSON.stringify(datum, null, 2));

Common Issues This Helps Debug

1. Script Data Hash Mismatch

The script data hash is computed from:

• All redeemers
• All datums in the witness set
• Cost models

If your witness sets differ, the hash will differ.

2. Wrong Owner in Datum

A common mistake is using the payment credential instead of the stake credential as the "owner" field in marketplace datums.

❌ TX1 owner: 0xc8d25b5c... (payment credential - WRONG)
✅ TX2 owner: 0x5139e814... (stake credential - CORRECT)

3. Input Ordering

Redeemer indices depend on the lexicographic ordering of inputs. If inputs are added in a different order, redeemer indices will be wrong.

4. Datum Witness vs Inline Datum

Some implementations add datums to the witness set, others use inline datums. The script data hash differs based on which approach is used.

Development

# Clone the repo
git clone https://github.com/ThomasEnoch/cardano-tx-decoder.git
cd cardano-tx-decoder

# Install dependencies
npm install

# Run in development mode
npm run dev decode 84a500...

# Build
npm run build

# Test locally
npm link
ctd decode 84a500...

License

MIT