Hex Converter
Decode Bitcoin OP_RETURN data and convert between hex and text
About Hexadecimal & OP_RETURN
Store arbitrary data in Bitcoin transactions since 2014
What is Hexadecimal?
Hexadecimal (hex) is a base-16 numbering system using digits 0-9 and letters A-F. Each hex digit represents 4 bits, so two hex digits represent one byte (8 bits). It's commonly used in computing to represent binary data in a more human-readable format. In Bitcoin, hex is used to represent transaction data, addresses, hashes, and embedded messages.
Bitcoin OP_RETURN
OP_RETURN is a Bitcoin script opcode that marks a transaction output as provably unspendable, allowing arbitrary data to be stored in the blockchain. Originally limited to 80 bytes when standardized in Bitcoin Core 0.9.0 (March 2014), the limit was increased to 83 bytes in Core 0.12.0, and dramatically expanded to 100,000 bytes in Bitcoin Core v30. It provides a standardized way to embed messages, timestamps, proof-of-existence, and other metadata on-chain. Popular uses include Omni Layer tokens, inscriptions, notarization services, and permanent messages.
Common Use Cases
- Proof of Existence: Timestamping documents and certificates
- Colored Coins: Representing assets and tokens on Bitcoin
- Omni Layer: USDT and other smart property tokens
- Messages: Permanent messages and announcements
- Inscriptions: Digital art, images, and large data files (up to 100KB)
- Ordinals: NFT-like inscriptions on satoshis
- Metadata: Additional transaction information
Technical Details
An OP_RETURN output starts with the opcode 6a in hex, followed by a push data opcode indicating the length, then the actual data. Historically limited to 80 bytes (later 83 bytes), Bitcoin Core v30 expanded the standard limit to 100,000 bytes per OP_RETURN output, enabling larger inscriptions and data storage use cases. Since OP_RETURN outputs are unspendable, they don't add to the UTXO set, making them less burdensome on full nodes than other data storage methods. Miners include these transactions based on fee rates just like any other transaction.
Decentralization & Freedom
Bitcoin's permissionless nature means anyone can include any valid transaction, including OP_RETURN data, as long as they pay the market fee rate. There is no central authority to decide what constitutes "spam" versus "legitimate" use. The fee market naturally regulates block space usage - when demand is high, fees rise and only the most valuable transactions get included. This self-regulating mechanism preserves Bitcoin's censorship resistance while maintaining its decentralized character.