# Stack Eliminators

<figure><img src="/files/rj2TcZOOULRXq02a9scd" alt=""><figcaption></figcaption></figure>

Just as important as creating copies is **removing unneeded data**. Eliminators **clean up the stack**, preventing it from growing unnecessarily large and keeping scripts **efficiaent**.

| Word       | Input | Output  | Description                     |
| ---------- | ----- | ------- | ------------------------------- |
| `OP_DROP`  | x     | Nothing | Removes the top stack item      |
| `OP_2DROP` | x1 x2 | Nothing | Removes the top two stack items |
| `OP_NIP`   | x1 x2 | x2      | Removes the second-to-top item  |

#### Common Patterns

**1. Discarding verification data:**

OP\_2DROP \<pubkey> OP\_CHECKSIG

After extracting needed information from **two data items**, drop them before proceeding to **signature verification**.

**2. Cleaning up after multi-signature:**

The **multi-signature opcode** (`OP_CHECKMULTISIG`) has a known bug requiring an **extra unused value** on the stack. Scripts typically use `OP_DROP` to **remove this dummy value** before continuing.

**3. Selective elimination with OP\_NIP:**

x1 x2 OP\_NIP // Result: x2

This is **more efficient** than `OP_SWAP OP_DROP` when you need to **keep the top item** but **remove what's beneath it**.

**Efficiency Note:** Each opcode adds to **script size and execution time**. Using `OP_2DROP` instead of two separate `OP_DROP` opcodes saves **one byte and one operation**.


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