Base64 Decoder

Base64 is a binary-to-text encoding method designed to represent binary data using a 64-character alphabet of printable ASCII characters. By converting arbitrary binary sequences into safe alphanumeric text, Base64 ensures that information remains intact when transferred across systems designed primarily for plain text, such as email (MIME), URLs, and JSON APIs.

When working with Base64 data, developers regularly perform Base64 encoding to prepare payloads and Base64 decoding to extract original strings or media files. A standard Base64 string uses uppercase letters A–Z, lowercase letters a–z, digits 0–9, and the two symbols + and /, with = appended as padding.

Base64 encoding works by grouping binary data into 6-bit units. Because a computer byte consists of 8 bits, Base64 takes 3 bytes (24 bits) and divides them into 4 six-bit chunks. Each 6-bit value (0 through 63) maps directly to one character in the Base64 alphabet:

Decoding reverses this transformation. The decoder reads four Base64 characters at a time, looks up their 6-bit values, combines them into a 24-bit stream, and unpacks the original three 8-bit bytes. When decoding text, these bytes are subsequently parsed using UTF-8 to reconstruct readable words, international scripts, and emoji.

This tool lets users decode Base64 directly in their browser without installing desktop software, command-line utilities, or browser add-ons.

Data confidentiality is essential when testing developer payloads and configuration tokens. Every decoding and encoding operation in this application runs locally inside your browser using the JavaScript V8 runtime.

No input strings, decoded text, or uploaded files are sent over the network to any remote backend server. You can even disconnect your internet connection after the page loads and continue decoding strings offline.