Script Validation Failures - What They Mean

8. Script Validation Failures — What They Mean

How Script Validation Works

When a node receives a transaction, it validates each input by:

1. Looking up the referenced UTXO's scriptPubKey.

2. Combining it with the input's scriptSig (and witness for SegWit).

3. Running the combined script through the interpreter.

4. Checking that the final stack top is truthy.

Validation failures are reported through testmempoolaccept or when a transaction is rejected from the mempool.

Common Reject Reasons and Their Meanings

| Reject Reason | Cause | |

Pro Tip

When debugging scripts, always start with a high-level disassembly before diving into the stack trace. Tools like bitcoin-cli decodescript are your first line of defense in identifying standard script patterns.