Base64 Encoder/Decoder — Free Online Base64 Encode Decode
Encode text to Base64 and decode Base64 strings back to plain text — 100% client-side using the browser's built-in btoa/atob functions.
Frequently Asked Questions
How Base64 Encoding Works
Base64 is a binary-to-text encoding scheme that represents binary data using a set of 64 printable ASCII characters. It was designed to safely transmit binary data through text-only channels, such as SMTP email and XML documents that cannot handle arbitrary binary content.
The encoding works by taking 3 bytes (24 bits) at a time and dividing them into four 6-bit groups. Each 6-bit value (0–63) maps to one character from the Base64 alphabet: A-Z (0-25), a-z (26-51), 0-9 (52-61), + (62), / (63). If the input isn't a multiple of 3 bytes, one or two = padding characters are appended.
Common uses: embedding images in HTML/CSS as data URIs (data:image/png;base64,...), encoding JWT payloads, transmitting binary API responses in JSON, storing SSH keys and TLS certificates in text files, and MIME email attachments. This tool uses the browser's built-in btoa()and atob() functions for zero-dependency Base64 encoding.