Ensure your file isn't accidentally named project.sb3.zip . Turn on file extensions in your operating system settings to see the true hidden extension.
: Right-click the file and select Rename . Change the ending from .zip to .sb3 . If you don't see the extension, enable "File name extensions" in the View tab of File Explorer.
Set the target output format dropdown to (if explicitly supported) or use an archive conversion pathway. convert zip to sb3
Check that the file named project.json is spelled correctly and sits in the root directory of your zip archive. Without this file, Scratch cannot interpret the project. The File Stays a ZIP File After Renaming
Because an SB3 file is a ZIP file in disguise, conversion is a simple matter of renaming the file extension— is required. Ensure your file isn't accidentally named project
If your file was originally an .sb3 project that was renamed to a .zip (or compressed directly from Scratch assets), you can convert it instantly by changing the extension. On Windows: Open and locate your .zip file.
Right-click the file and select Rename (or press F2 ). Change the ending from
Ensure your ZIP file contains the necessary Scratch assets at the root level (e.g., project.json and asset files like .svg or .wav ) rather than being inside a subfolder. Right-click the file and select . Change the extension from .zip to .sb3 .
Always keep a backup of your original ZIP file before renaming or modifying it. One wrong compression method can break the project structure, but fixing it is usually as simple as re-zipping the contents correctly.
First, let’s look under the hood. When you save a project in Scratch 3.0, the software creates a file ending in .sb3 . But what is inside that file?