Why can't projects made in Scratch Modifications be shared to the Scratch Website?

Sharing projects to the official Scratch website from Scratch Modifications is against the Scratch Terms of Use. Even if it weren't, they would still be incompatible.

Scratch Modifications cannot share projects to the Scratch Website for a few reasons.

Reasons

Compatibility

Features

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 online or the offline editor. 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.

File Type

Scratch uses the file extension .sb3 for projects, and .sprite3 for sprites. Many Scratch modifications will change the project extension, and some have a different sprite extension as well. Scratch can open files with any extension, but a modification might change the file format in a way that makes it incompatible with Scratch.

Terms of Use

The Scratch Terms of Use disallow uploading projects created using Scratch modifications.

License

This article or section documents something not included in the current version of Scratch (3.0). It is only useful from a historical perspective.

The Scratch 1.x source code was released under the Scratch Source Code License, which prevents modified versions of Scratch from uploading projects to the website.

Mod Share

Main article: Mod Share

Projects made in supported modifications can be uploaded to Mod Share, a user made site for this purpose.