Base64 encoder and decoder

Encode any text to Base64 or decode Base64 back to readable text, with correct UTF-8 handling and an optional URL-safe alphabet.

🔒 Runs entirely in your browser. Nothing you paste is uploaded or sent to a server.

How Base64 works

Base64 turns arbitrary bytes into 64 safe ASCII characters (A-Z a-z 0-9 + /). Every 3 bytes become 4 characters, so the output is about 33% larger. If the input length is not a multiple of 3, the output is padded with one or two =. Base64 is an encoding, not encryption: anyone can decode it, so never treat a Base64 string as hidden.

The decoder accepts both variants, ignores whitespace and line breaks, adds missing padding, and strips a data:...;base64, prefix.

Text vs. bytes (UTF-8)

Base64 encodes bytes, so text has to be turned into bytes first. This tool uses UTF-8, which is what nearly every API expects. The browser's built-in btoa("é") works only for Latin-1 and throws on characters like ✓ or emoji, which is why naïve online encoders break. If decoded bytes are not valid UTF-8 the tool tells you and shows them as hex: the data is probably binary (an image, gzip, a key) or in another encoding such as Latin-1, the same situation that causes Python's UnicodeDecodeError.

Command-line equivalents

Use echo -n: without it the trailing newline gets encoded too, a common reason a Kubernetes Secret value "doesn't match" (CreateContainerConfigError is a related symptom). An HTTP Basic auth header is just base64(user:password), which is why Git hosts switched to tokens (password authentication removed).

Last updated 2026-11-01.