This time I would like to introduce you a really simple and useful tool you can use to decode / encode web URLs. You can find this tool in the following URL: http://meyerweb.com/eric/tools/dencoder/. For instance, as an example of how to use, just paste in the URL Decoder/Encode area the URL you want to decode/decode. In my case, I have pasted the URL of a SharePoint Add-in (A Provider-Hosted one)
If you click the “Decode” button, you will get a Clean URL and for instance the value of some SharePoint Add-in parameters such as SPHostUrl, SPLanguage, etc.