Drag and drop a file in the box below to encode it using base64 encoding. All processing is done in-browser. No data is sent anywhere. This was thrown together in just a few hours (including the time to learn how base64 encoding works and how to read files in javascript), so it has not been optimized. Large files may break it.
I made this out of spite because I needed to encode something and did a quick search and the first several results were suspicious websites clogged full of ads.
This page works as a standalone html file. All code and styles are in-line, so it can easily be downloaded and run locally.