For general instructions on how to register iExplorer, please see How do I register iExplorer?.
If your 25 digit registration code is coming up as Invalid in iExplorer, you'll first want to make sure you are using the major version of iExplorer that you purchased. For most people, that will be version 3 which has an app icon with a blue background. You can download the most recent version of iExplorer 3 from the direct download links below:
iExplorer 3 for Mac: https://www.macroplant.com/iexplorer/download-ie3-mac
iExplorer 3 for Windows: https://macroplant.com/iexplorer/download-ie3-pc
iExplorer 4 uses a different registration code than version 3 since it's an all new, major version of the software that adds iOS 10 support and includes many other performance and UI enhancements. iExplorer 4 is the version that will be downloaded from our site from most of our Download buttons now. If you own an iExplorer 3 license and would like to upgrade to iExplorer 4 at a discounted price, you can go to the link below and enter the same email you used when purchasing iExplorer 3. The discount will be determined by how long ago you purchased major version 3:
If you still can't register iExplorer using the registration code that corresponds to the major version of iExplorer that you own and are using, make sure you are entering your iExplorer code exactly by using copy & paste to avoid any typos such as mistaking a 5 for an S or a 2 for a Z, etc. If it still won't accept your registration code, try completely closing iExplorer, reopen it, and then copy & paste your code into iExplorer again.
Mac OS 10.6 users
If you have a Mac still running OS 10.6 Snow Leopard then you'll need to install a more recent version of iExplorer 3 that is specifically built for 10.6 users and will definitely let you register it with our new iExplorer 4 codes. You won't be able to get this update within the app though FYI. You must download it from our website, but to make it easier, here's a download link for version 126.96.36.199 that will automatically start the download for you:
(choose to Replace the iExplorer in your Apps folder when prompted)
Apple officially stopped supporting Mac OS 10.6 in early 2014 and then cut iOS compatibility for it starting with iOS 9 in 2015 when they didn't release an iTunes compatible version to connect and sync with iOS 9 and then iOS 10 too. This is most likely due to the fact that 10.6 is now over 7 years old and six OS versions back from their newest MacOS Sierra (10.12), so we also stopped releasing iExplorer updates for 10.6 beginning with iExplorer 3.9 because 10.6 uses some older frameworks that really limit our development options and the enhancements we can add to iExplorer.