Before diving into the conversion process, it helps to understand what these files actually are.
Click the Convert button. The website will process the file instantly.
: This usually happens if the project.json file is missing or if the ZIP was created by compressing a folder rather than the files inside the folder.
| Current Format | Action | |----------------|--------| | Valid SB3 renamed to .ZIP | Rename back to .sb3 | | Folder with project.json | ZIP contents → rename to .sb3 | | SB2 or older ZIP | Use Scratch’s menu |
Windows will warn you that changing the extension might make the file unusable. Click Yes to confirm. Locate Your File: Open Finder and find your ZIP archive.
: A text file containing all the scripts, block logic, variable data, and references to assets [1].
Download the newly generated .sb3 file back to your device.
Right-click the file and select Rename (or press F2 ).
A valid Scratch project must contain a file explicitly named project.json . If this file was deleted, corrupted, or renamed, the .sb3 file will not open.
Converting a file back into an SB3 file is a common task for Scratch developers who want to manually edit project code or assets . Since an .sb3 file is essentially a renamed ZIP archive containing a project.json file and various media assets, the "conversion" is primarily about proper re-packaging. Method 1: Manual Renaming (Fastest)
: The core file containing all scripts and metadata.
