Is the encoding standard Base64?

Yes — same as data:image/…;base64,… URLs used in HTML.

How big can the file be?

Anything up to a few MB; the encoded string will be ~33% larger.

No, encoding runs in the browser.

Convert an image into a Base64 data URL for embedding in HTML or CSS.

Your data is processed in your browser and not uploaded.

Reads any image as a Base64-encoded data URL you can inline in web pages or emails.

Compress JPG/PNG images in your browser with an adjustable quality slider.

Encode text to Base64 and decode it back.