Base64 Encoder & Decoder — Free Online

What is Base64 encoding?

Base64 is a way to represent binary data as ASCII text. It's commonly used in data URLs, email attachments, API tokens, and embedding images in CSS/HTML. This tool encodes and decodes Base64 with full Unicode support.

Base64 encoding works by taking groups of 3 bytes (24 bits) and splitting them into 4 groups of 6 bits. Each 6-bit group maps to one of 64 printable ASCII characters (A-Z, a-z, 0-9, +, /). If the input length is not a multiple of 3, the output is padded with '=' characters. This encoding increases data size by approximately 33%.

Developers use Base64 encoding to embed small images as data URIs in HTML/CSS (avoiding extra HTTP requests), encode binary attachments in email (MIME encoding), pass binary data through JSON APIs that only support text, create HTTP Basic Authentication headers, and encode JWT token segments. It is also used in configuration files that need to store binary data.

Only use Base64 for data under 10 KB when embedding in HTML or CSS — larger Base64 strings bloat the document and cannot be cached separately by browsers. Remember that Base64 is encoding, not encryption — anyone can decode it instantly. For actual security, use encryption tools like AES. When working with URLs, use Base64url variant (replacing + with - and / with _) to avoid URL-encoding issues.

Browser developer consoles offer btoa() and atob() functions for Base64, but they only handle ASCII text. Command-line tools like base64 on Linux/Mac work with files but lack a visual interface. This tool handles full Unicode text and provides instant encode/decode with a clean interface — useful for quick debugging without remembering function names or terminal syntax.