Scratch has a limited feature set. One of the purposes of modifying the source is to add features. Because these features were not programmed into Scratch, they would not be compatible with either the Scratch application or the online players. Furthermore, a Scratch modification may contain features more prone to security or safety risks, such as online compatibility, and Scratch is designed to be safe and for all ages.
Scratch uses the file extension
.sb for projects, and
.sprite for sprites. Many Scratch modifications will change the project extension, and some, such as BYOB, have a different sprite extension as well. Scratch will not recognize or open other filetypes. Even if the project extension is the same, the header may be different.
The source code license itself prevents modified versions of Scratch to be uploaded to the website.
- Main article: Mod Share
Projects made in supported modifications can be uploaded to Mod Share, a user made site for this purpose.