How many sites can I use my subscription key on?

One valid subscription key can be used on an production site and a test/development site. This allows you to test your extensions in a live and development environment simultaneously.

If you you have a 1-site subscription, then 1 production site and 1 test/development site. If you have a 5-site subscription, then 5 production sites and 5 test/development sites. Etc…