Base64 Encoder/Decoder

Base64 encoding converts binary data into a text representation using 64 printable ASCII characters: A-Z, a-z, 0-9, plus (+), and forward slash (/), with equals (=) used for padding. The name comes from the 64-character alphabet used. Every 3 bytes of binary data become 4 Base64 characters, which means Base64-encoded data is approximately 33% larger than the original. This size increase is an acceptable tradeoff when you need to transmit binary data through systems designed for text — email systems, URLs, JSON fields, XML documents, and HTML attributes. The encoding process takes each group of 3 bytes (24 bits) and splits it into four 6-bit groups. Each 6-bit value maps to a character in the Base64 alphabet. If the input isn't divisible by 3, padding characters (=) are added to make the output length a multiple of 4. The AllTools Base64 Encoder performs all encoding and decoding in the browser using JavaScript's built-in btoa() and atob() functions for text, and FileReader API for binary files. Nothing is transmitted — your data is encoded and decoded entirely in your browser's memory.

Base64 encoding appears throughout modern web development in specific contexts where binary data must be represented as text. Data URIs embed images directly in HTML and CSS without separate HTTP requests — a small icon encoded as Base64 in a CSS background-image eliminates one network round trip. Email attachments are Base64-encoded since SMTP was designed for 7-bit ASCII text — email clients transparently encode and decode attachments during sending and receiving. JSON APIs that need to transfer binary files (images, documents, audio) often Base64-encode them to avoid multipart form complexity. JWT tokens encode their JSON payload in Base64url format (a URL-safe variant that replaces + with - and / with _). Basic HTTP authentication encodes username:password as Base64 in the Authorization header. Canvas element's toDataURL() method returns Base64-encoded image data for in-browser image processing. SVG data URIs in CSS backgrounds embed vector graphics as Base64. When debugging API responses, developers frequently need to decode Base64 values to inspect the underlying data — the AllTools decoder provides instant results without copying data to external services.