URL Decode is a text transform, not a lock
Turn %20 and similar codes back into readable text.
Decoding happens in the browser.
Do not treat this as security
A string that was encoded twice needs to be decoded twice. Look at the result before you assume it is finished.
Why URL Decode is its own job
URL Decode sits on this site because URL Encoded and Text are not interchangeable, even when they look similar in a file list. Turn %20 and similar codes back into readable text. People encode a parameter before they paste it into a link, or decode a link they received. Font conversions and developer utilities are paste boxes, not file uploads.
Decoding happens in the browser.
The URL Encoded file you already have
URL encoding turns spaces and symbols into percent sequences so a query string stays intact. Encoding twice produces a broken link. Decoding a string that was not encoded mangles it.
Keep the original URL and compare one parameter after you decode.
What a Text result is for
The download has to be Text, because that is the format the next step named. Font conversions and developer utilities are paste boxes, not file uploads. Nothing is uploaded. You can try one line first.
If the output is empty or identical, the input was already in the target form or it was not the encoding you selected.
How to tell that URL Decode worked
URL Decode is worth using only when Text is what the next step actually named. Turn %20 and similar codes back into readable text. What you get from URL Decode: Decoding happens in the browser. Before you trust it: A string that was encoded twice needs to be decoded twice. Look at the result before you assume it is finished. The text stays in the browser. Try one line you can check before a whole document. Do not paste passwords. A second pass rarely helps. If the first Text file is rejected, read the error from the program that rejected it. Another conversion of a bad result usually makes the file worse, not more compatible. When you are done, you should still have the URL Encoded original and one Text download that you have opened. If those two are the same kind of failure, this was the wrong tool and the page above is the place that says so. URL Decode is a text transform for a payload you already understand. Encoding is reversible on purpose. It is not a lock, not a password store, and not a place for production secrets. Check the output before you paste it into a live request, and do not run the tool twice on text that was already encoded.
Here is the decision for URL Decode. You start with URL Encoded and you stop when a real program accepts Text. Spaces, question marks, and non-ASCII text survive in a query string after encoding. The wrong input type produces the wrong output, and the page cannot guess which font you used. If those two sentences describe a tradeoff you do not want, do not convert. Renaming the extension by hand will not do this job. Running the tool twice on its own output will not do it either.
A string that was encoded twice needs to be decoded twice. Look at the result before you assume it is finished.
A related step, if you still need one, is URL Encode.
Other jobs start from the homepage, where each tool is named for the conversion it actually does.