Base64 Encoder/Decoder

Base64 is a binary-to-text encoding scheme that represents binary data using 64 printable ASCII characters (A-Z, a-z, 0-9, +, /). It was designed to safely transport binary data over channels that only handle text — primarily email (via MIME) and HTTP headers. Today Base64 appears in dozens of everyday contexts: it's how images are embedded directly in HTML and CSS as data URIs, how Basic Auth credentials are formatted in HTTP headers, how SSH public keys and TLS certificates are stored in PEM files, how JWTs encode their header and payload, and how binary attachments are transmitted in email.

The encoding works by taking 3 bytes of binary data (24 bits) and breaking them into four 6-bit groups, each mapped to one of the 64 printable characters. This means Base64-encoded data is always approximately 33% larger than the original binary data. The `=` padding characters at the end of a Base64 string ensure the output length is always a multiple of 4.

Common pitfalls: standard Base64 uses `+` and `/` as the 62nd and 63rd characters, but these are not URL-safe (they have special meaning in URLs). URL-safe Base64 (Base64url) replaces them with `-` and `_`. If you're working with JWTs or URL parameters, check which variant you need. Also note that Base64 is encoding, not encryption — it is trivially reversible and provides zero security.

This tool handles standard Base64 in both directions in real time: type or paste in either panel and the other updates instantly.