Encodr allows for the effortless encoding of binary file types (not to mention pretty much anything else) into the data:... URI format. It works with Pale Moon, and is distributed under the GNU General Public License, V3.
Do you want to encode images, other files, HTML, plain text, or just about anything into a data:... URI? Then you're in luck! Encodr allows you to do just that with an easy-to-use interface.
Simply open a new Encodr tab (using the toolbar button or entry in the Tools menu), click on the file target box to open a file browser, and navigate to the file you wish to encode. You can also drag/drop files onto the target box! If the file selected is an image file, a preview of it will appear before you encode it. Then just click the Encode button and the encoded data:... URI will appear in the box below.
Note that you can choose whether to encode in base64, or just use URI encoding. In both cases, Encodr will generate a valid URI, but base64 encoding may result in a more compact URI for large amounts of binary data. In addition, you don't have to encode a file - you can also enter text in the Input textbox and encode that.
Encodr will try to determine the content type of the data to encode based on the file selected, but you can override that by modifying the text in the Content Type box. You don't need to add 'base64' to the content type, though, as this will automatically be added by Encodr when it's encoding to base64 (ie. the Base64 checkbox is checked).