Encode text to Base64 or decode Base64 back to text — instantly, client-side, no server.
Base64 encodes binary data as ASCII text using 64 printable characters. 3 input bytes become 4 output characters, inflating size by ~33%.
Embedding images in CSS/HTML (data:image/png;base64,...), encoding binary in JSON, HTTP Basic Auth headers, JWT tokens.
Standard Base64 uses + and / which break URLs. URL-safe Base64 replaces them with - and _. Used in JWTs.
The trailing = padding aligns output to 4-byte blocks. It's optional for decoding and omitted in many APIs (e.g. JWT).