> ## Documentation Index
> Fetch the complete documentation index at: https://docs.theblockchainlibrary.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Bytecode

> Low-level machine-readable instructions produced by compiling smart-contract source code for execution by a virtual machine.

# Bytecode

Low-level machine-readable instructions produced by compiling smart-contract source code for execution by a virtual machine.

## Definition

Low-level machine-readable instructions produced by compiling smart-contract source code for execution by a virtual machine.

## Why it matters

Smart-contract concepts are essential for understanding programmable blockchain applications.

## How it works

A compiler takes source code and performs a series of optimizations to output a hex string. This string contains opcodes like PUSH, POP, ADD, and SSTORE. When a transaction calls a contract, the EVM loads this bytecode into its execution environment and runs these opcodes in order.

## Real-world example

When you deploy a contract to Mainnet via Etherscan or Hardhat, the resulting hex data block in the transaction receipt is the bytecode deployed to the blockchain.

## Advantages

* Highly efficient for machine execution
* Immutable and tamper-proof
* Ensures consistent behavior across different nodes

## Limitations

* Difficult to read or debug
* Reverse engineering is complex
* Limited access to high-level logic

## Common misconceptions

* People often think bytecode is the same as the Solidity source code, but it is actually the compiled output.
* Some believe bytecode is always readable by humans, but it is meant for the machine, not for developers to edit directly.

## Related knowledge

* [ABI](/generated/v2/glossary/abi) — term
* [Smart Contract](/generated/v2/glossary/smart-contract) — term
* [Solidity](/generated/v2/resources/solidity) — term

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**Canonical knowledge ID:** `glossary:bytecode`