Base64 Encoder / Decoder: Frequently Asked Questions

No. Base64 is an encoding scheme — anyone can decode it without a key. It is used to safely represent binary data as text, not to protect it from unauthorized access. Do not use Base64 as a security measure.

Base64 encodes every 3 bytes of input into 4 characters of output — a 33% size increase. This is a fundamental property of the encoding, not a bug.

URL-safe Base64 replaces the + and / characters with - and _ respectively, producing a string that is safe to include in URLs and file names without percent-encoding. The padding = characters are also usually omitted.

Base64 works in groups of 3 bytes. If the input length is not a multiple of 3, padding characters (=) are added to make the output a multiple of 4 characters. One = means the last group had 2 bytes; == means it had 1 byte.

This tool encodes text to Base64. For file encoding, you would typically use a command-line tool (base64 command on macOS/Linux) or a dedicated library. The output is identical — Base64 is Base64 regardless of the source.

Standard Base64 uses A-Z, a-z, 0-9, +, /, and = for padding. URL-safe Base64 uses - instead of + and _ instead of /. Any other character indicates an invalid or corrupted Base64 string.