Ensure your file isn't actually named project.sb3.zip . Turn on file extensions in your OS settings to be sure.
If you prefer an automated tool, several browser-based options handle the conversion without requiring you to upload files to a server, which protects your privacy. convert zip to sb3 updated
If Scratch refuses to open your converted .sb3 file, check the following: Ensure your file isn't actually named project
Extract the ZIP contents and verify that a project.json file exists at the root level. For .sb3 files that won't open, try loading them through Scratch's "File → Load from your computer" option rather than double-clicking. If Scratch refuses to open your converted
Scratch 3.0 expects the project.json file to be at the root of the ZIP archive, not inside an extra folder. By selecting the internal files directly, you recreate the correct internal structure.
Select all items inside the folder simultaneously (including project.json and all asset files). Right-click the selected items. : Select Compress to ZIP file . On macOS : Select Compress [Number] Items .
By following these steps, you should be able to convert your zip file to an Sb3 file and access your Scratch project in the Scratch programming environment.