Paste Base64 and read what is inside. Line breaks and stray spaces are ignored, so you can paste straight out of a header or a config file.
This page loads no libraries at all — the work is done by the browser itself.
Your file is read on your own machine and never sent anywhere — open your
browser's network tab and watch while you use it.
Questions
It says my input is invalid — why?
Something is not valid Base64: a truncated string, or a URL-safe variant using - and _ instead of + and /.
Can I decode a Base64 image?
A data URL of an image decodes to binary, which will not read as text. The image converter is the tool for that.
Other text & code tools
Everything here is free and works the same way — in your browser.