Base64 Encode / Decode

How it works

Base64 encodes binary data by grouping the input into 24-bit blocks (3 bytes) and mapping them to four 6-bit values. Each 6-bit value is used as an index into a 64-character alphabet (A–Z, a–z, 0–9, +, /). If the input length is not a multiple of 3 bytes, the output is padded with one or two = characters.

• Text is first converted to bytes using UTF‑8 (so emojis and non‑ASCII characters are preserved).
• Every 3 input bytes → 4 output characters. 1 leftover byte → 2 chars + ==; 2 leftover bytes → 3 chars + =.
• Decoding reverses the process, turning 4 Base64 chars back into 3 bytes, then decoding as UTF‑8 text.

Base64URL: JWTs and URLs often use a URL‑safe variant where + → -, / → _, and padding = is optional. This tool targets standard Base64; for URL‑safe, convert the alphabet accordingly.