Base64 Encoder / Decoder
Encode or decode Base64 text and files — live, URL-safe, data URIs, 100% client-side
Frequently Asked Questions
Everything you need to know about this tool
No. Everything happens in your browser tab. You can verify in DevTools → Network — no request is fired when you type.
When the encoded value will live in a URL, a JWT, an S3 key or anywhere that treats "+" and "/" as reserved characters. URL-safe uses "-" and "_" instead and drops the "=" padding.
The data is probably Latin-1 (or Windows-1252) and not UTF-8. Switch the Charset selector and the output will render correctly. Binary files should be used via the File tab instead.
Up to roughly 100 MB works well on desktop browsers. Above that you may hit memory limits — the whole file needs to live in an ArrayBuffer to produce a data URI.
That is inherent to Base64: three input bytes become four ASCII characters, plus a data-URI header for the File tab. We show the original and the encoded size side-by-side so you can see exactly what you are about to copy.
Yes — small Text-mode inputs are mirrored to the address bar (capped so we never create multi-kilobyte URLs). The File tab never touches the URL; binary blobs belong in your clipboard, not your history.