Base64 Encoder & Decoder

Base64 turns any data into plain ASCII letters, digits and a few symbols, so it can travel safely through systems built for text, such as email, JSON, XML and HTTP headers. This tool encodes and decodes text with correct UTF-8 handling, so accented letters, emoji and non-Latin scripts survive the round trip.

Common uses

• Decode the payload of a JSON Web Token (JWT) to inspect its claims.
• Encode credentials for HTTP Basic authentication headers while testing.
• Decode Base64 strings found in emails, logs, API responses or configuration.
• Encode small snippets for data URIs, Kubernetes secrets or environment variables.

Tips for best results

• Data grows by about 33% when Base64-encoded – keep large files as binary where possible.
• Decoding ignores whitespace and line breaks, so you can paste wrapped MIME text.
• Use URL-safe mode for anything placed in a URL or file name.
• For images and files, use the Image to Base64 tool, which creates data URIs.

How Base64 works

Every three bytes of input (24 bits) are split into four groups of six bits, and each group is mapped to one of 64 characters: A–Z, a–z, 0–9, + and /. When the input is not a multiple of three bytes, = signs pad the end. Because text is converted to UTF-8 bytes first, “é” becomes two bytes and “👍” four, which is why short non-English strings can produce longer Base64.

Common pitfalls

Many simple tools use the browser's btoa function directly, which fails on any character outside Latin-1. This encoder converts text to UTF-8 first, matching how servers and most programming languages behave. If decoded text looks garbled, the original data was probably binary (an image or a zip) or used a different character set, such as Windows-1252 or Shift_JIS.