Base64 Encoder / Decoder

Base64 is a binary-to-text encoding scheme that converts binary data into a string of printable ASCII characters, making it safe to transmit through text-based systems that cannot handle raw binary. The name refers to the 64 characters used: uppercase letters A-Z, lowercase letters a-z, digits 0-9, plus sign, and forward slash. Every three bytes of binary input are converted into four Base64 characters, making the output approximately 33% larger than the input.

Base64 was originally developed as part of the MIME email standard to allow binary files such as images and documents to be attached to emails that could only reliably transmit ASCII text. It has since become a universal encoding used across web development, cryptography, and data storage. The equals signs at the end of a Base64 string are padding characters added when the input length is not divisible by three.

The most frequent web use of Base64 is embedding images directly in HTML or CSS as data URIs, eliminating a separate HTTP request to load the image. This is useful for small icons, inline SVGs, and email templates where external image hosting is unreliable. JSON APIs use Base64 to transmit binary file data within a JSON payload, since JSON only supports text. HTTP Basic Authentication encodes credentials as Base64 in the Authorization header.

Cryptographic keys, certificates, and SSH public keys are commonly distributed in Base64-encoded PEM format. JWT tokens use a URL-safe variant of Base64 to encode their header and payload. It is critical to understand that Base64 is encoding, not encryption — any Base64 string can be decoded by anyone instantly with no key required. Never use Base64 to protect sensitive data.