Seems it depends on your market. I'm doing desktop consumer software, and the licensing is all in-house stuff. Rather than being uncrackable, I'm more focused

Seems it depends on your market. I'm doing desktop consumer software, and the licensing is all in-house stuff. Rather than being uncrackable, I'm more focused on usability and keeping honest people honest. I use simple short serial codes, automatically generated & able to be emailed again when customers inevitably lose them. (Try to avoid doing manual generation & manual lookups, it will save you a ton of support time.) I avoid characters that are easily confused & can cause support issues, so no O and 0, no I and 1, no 5 and S etc. As part of usability, I like how iZotope include the name of the product in their serial codes (eg SN-MYPRODUCT3-XXXXX). I've had issues with customers mixing up serial codes, and it helps if you can give them a hint/prompt (eg your key begins with SN-MYPRODUCT3). If your goal is just to put a small indie product out and sell it, you don't have to over engineer the licensing. I've seen apps where every customer got the same unlocking code, and it still sold plenty of copies. Brandon Staggs' article on implementing serial codes is still my favorite: http://www.brandonstaggs.com/2007/07/26/implementing-a-partial-serial-number-verification-system-in-delphi/ http://www.brandonstaggs.com/2007/07/26/implementing-a-parti...