Hexadecimal

Overview

Hexadecimal provides a readable representation of binary values. Four bits map to one of sixteen symbols, and eight bits form a byte represented by two hex characters. The byte value 255, for example, appears as `ff`. Uppercase and lowercase letters usually represent the same numeric value unless an address format adds case-specific rules.

Ethereum JSON-RPC commonly prefixes hex values with `0x`. Unformatted byte arrays use two hex digits per byte, while quantities use rules that avoid unnecessary leading zeros. A developer must know whether a field represents raw bytes, an unsigned number, an address, or encoded contract data because the same visible characters can be interpreted differently.

Hex is a form of Data Encoding, not encryption. Anyone can decode it, and converting bytes to hex does not add security. It is popular because debugging tools can display exact values without the ambiguity of text character encodings and because boundaries between bytes remain visible.

Common errors include dropping leading zeros, confusing byte order, adding or removing the `0x` prefix incorrectly, and treating a hex string as human text. Transaction hashes and fixed-length addresses often require exact byte length, so an apparently minor formatting change can produce an invalid or different value.

Payment integrations should preserve raw values and use typed parsers rather than manual string manipulation. When presenting calldata or a raw transaction to users, software should decode the business meaning where possible. A long hexadecimal string is precise for machines but poor evidence of informed authorization. The hex text should always be decoded back into the intended Binary Encoding before protocol fields are validated.