Base64 Text & URL-Safe Encoder/Decoder

What base64 is for

Base64 encodes binary data into 64 printable ASCII characters so it survives text-only channels: email attachments (MIME), HTTP Basic auth (user:pass), data URIs in CSS/HTML (data:image/png;base64,...), and the base64url segments of JWTs. Every 3 bytes become 4 characters, so output is ~33% larger than input.

Standard vs URL-safe

• Standard base64 uses +/ and = padding — fine in bodies and headers, but + and / have special meaning in URLs.
• base64url swaps + → - and / → _, and usually drops padding — this is what JWT segments and ?token= params use.
• The tool auto-detects and decodes both forms; the checkbox controls the encode output.

Unicode note

Text is encoded as UTF-8 first, so emoji and CJK work correctly both ways — a common bug with naive encoders that mangle non-ASCII input.

Pair with the JWT Decoder if you're working with tokens (all three segments are exactly base64url).