Base64 Encoder and Decoder

Base64 represents binary data with 64 printable characters (A-Z, a-z, 0-9, + and /), which is why it appears in email transport, inline web images, API payloads and JWT tokens.

• Text encoding: turn any string, Chinese included, into Base64
• Text decoding: restore Base64 to readable text with automatic UTF-8 detection
• Image to Base64: upload an image and get a data:image/...;base64,... Data URI ready for CSS or HTML
• Base64 to image: rebuild and preview an image from a Base64 string

When to use it

• Inline small images in HTML or CSS to cut HTTP requests
• Embed images in email bodies
• Move binary data through an API
• Encode the header and payload of a JWT

All encoding and decoding runs in the browser; nothing is uploaded.

Base64 notes

• How it works: every 3 bytes (24 bits) become four 6-bit groups mapped to 64 printable characters
• Size change: encoded data grows by about one third, 3 bytes to 4 characters
• Padding: when the input is not a multiple of 3 bytes, = fills the gap, so strings often end in = or ==
• Data URI: the data:image/png;base64,... form embeds directly in HTML or CSS