OP_VERIFY ​

OP_VERIFY is an opcode that allows for quick validation of conditions without explicitly ending the script. It's used to ensure certain requirements are met.

Operation ​

1. Pop the top stack value.
2. If the value is 0 or an empty string, the script immediately fails and the transaction is considered invalid.
3. If the value is non-zero, continue executing the script, with the item now removed from the stack.

The primary use of OP_VERIFY is to verify that a certain condition holds without having to use conditional opcodes. If the condition does not hold, the script will terminate at the OP_VERIFY step.

Notes ​

• The opcode can be thought of as a shorthand for OP_IF OP_DROP OP_ELSE OP_RETURN OP_ENDIF.

Examples ​

Example 1 ​

In a hypothetical script where a 1 is pushed onto the stack, the following would pass verification:

# ASM script
OP_1 OP_VERIFY

# Raw script
5169

# Final stack
(empty, since the 1 was popped by OP_VERIFY, but the script succeeds)

Example 2 ​

For a script that starts by pushing 0 onto the stack, the script would fail at the verification step:

# ASM script
OP_0 OP_VERIFY

# Raw script
0069

# Script result
Script fails at OP_VERIFY.