Base64 Encoder & Decoder

Encode and decode Base64 and base64url, including non-ASCII text. Runs entirely offline. No tracking, no permissions.

Base64 conversion that handles the cases most quick implementations get wrong. • Encode and decode standard Base64 • URL-safe alphabet (- and _) for URLs, filenames and JWT segments • Optional unpadded output • Correct handling of non-ASCII text — btoa alone throws on anything above Latin-1, so text is encoded through TextEncoder first • One-click copy About padding A Base64 string whose length leaves a remainder of 2 or 3 decodes fine without padding, and this decoder accepts that. A remainder of 1 is impossible to produce and is rejected with a clear message rather than silently returning wrong bytes. Nothing is sent anywhere. No permissions, no network requests, no storage.