Base64 Encode / Decode

Base64 Encode Decode converts plain text into Base64 and turns Base64 strings back into readable text, all inside your browser. Base64 is an encoding scheme that maps binary data onto 64 safe ASCII characters (A-Z, a-z, 0-9, plus + and /), padding the output with = signs when the input length is not a multiple of three bytes. Every three bytes of input become four Base64 characters, which is why encoded output is always about 33% larger than the original. This tool uses the browser's native btoa and atob routines (with proper UTF-8 handling via TextEncoder/TextDecoder) so multibyte characters like emoji, accented letters, and Cyrillic survive the round trip intact. Because everything runs client-side in JavaScript, nothing you type or paste is ever uploaded to a server, logged, or stored. You can even disconnect from the internet after the page loads and it keeps working. Real-world uses are everywhere: embedding a small image as a data URI in CSS or HTML, encoding credentials for an HTTP Basic Authorization header, inspecting the payload of a JWT, wrapping binary attachments for email (MIME), passing JSON safely through URL parameters, or storing config blobs that must remain plain ASCII. Developers debugging APIs, sysadmins reading tokens, students learning how encoding works, and anyone who received a mysterious "SGVsbG8=" string all benefit. A practical tip: Base64 is encoding, not encryption, so never treat it as a way to hide secrets, anyone can decode it in one click. If decoding fails, the input usually contains stray whitespace, line breaks, or URL-safe characters (- and _) that need converting back to + and /. For binary files, encode the raw bytes rather than a text interpretation to avoid corruption.