# Practical Application: Format Validation

Size checking enables precise data format requirements:

### Example: Fixed-length identifier

```
OP_SIZE OP_32 OP_EQUAL OP_VERIFY
```

This ensures the input is **exactly 32 bytes**—useful for validating hashes, IDs, or other fixed-format data.

### Example: Range validation

```
OP_SIZE OP_4 OP_GREATERTHANOREQUAL 
OP_SIZE OP_8 OP_LESSTHANOREQUAL 
OP_BOOLAND OP_VERIFY
```

This ensures input is **between 4 and 8 bytes**—useful for validating integers or codes that must fall within a specific size range.

 

**Use cases:**

* **Hash validation:** Ensure SHA-256 outputs are exactly 32 bytes
* **Protocol identifiers:** Verify token IDs match expected format
* **Form validation:** Check user inputs meet length requirements
* **Data structure parsing:** Confirm fields match specification

 

| Data Type          | Expected Size | Validation Pattern                  |
| ------------------ | ------------- | ----------------------------------- |
| SHA-256 hash       | 32 bytes      | `OP_SIZE OP_32 OP_EQUAL`            |
| RIPEMD-160 hash    | 20 bytes      | `OP_SIZE OP_20 OP_EQUAL`            |
| 4-byte integer     | 4 bytes       | `OP_SIZE OP_4 OP_EQUAL`             |
| Variable (max 100) | ≤100 bytes    | `OP_SIZE OP_100 OP_LESSTHANOREQUAL` |


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