Encode, decode, and convert between data formats. Use when working with Base64, URL encoding, hex, Unicode, JWT tokens, hashing, checksums, or converting between serialization formats like JSON, MessagePack, and protobuf wire format.
Base64 increases data size by ~33%. Use it for embedding binary data in text formats (JSON, XML, email), not for compression or encryption.
Base64url (RFC 4648) uses - and _ instead of + and /, and omits padding =. JWTs and URL parameters use this variant.
SHA-256 is the standard for integrity checks. MD5 is fine for dedup and non-security checksums but broken for cryptographic use.
JWTs are signed, not encrypted. Anyone can decode the header and payload. Only the signature verifies authenticity. Never put secrets in JWT claims.
When files display garbled text (mojibake), the problem is almost always wrong encoding assumption. Check with file -bi and re-read with the correct encoding.
xxd -p (plain hex) and xxd -r -p (reverse) are the fastest way to convert between binary and hex on the command line.
URL-encode with encodeURIComponent (JavaScript) or urllib.parse.quote (Python), not by hand. Manual encoding misses edge cases.
