Set your ZIP compression level. For maximum compatibility and speed, standard "Deflate" compression is ideal. Rename the output file from archive.zip to project.sb3 . Automated Batch Conversion Using Python
Explain how to (sb2) to high-quality sb3.
Confirm the change when your operating system warns you about changing file extensions. Method 2: Utilizing Scratch Project Packagers
: An .sb3 file is a ZIP archive containing a project.json file (code and metadata) and various media assets (costumes, backdrops, and sounds).
| Mistake | Quality Impact | Fix | |---------|----------------|-----| | Using built-in macOS “Compress” function | Adds __MACOSX and .DS_Store files → project fails to load | Use Keka or Terminal zip -X | | Renaming .rar or .7z to .zip | Corrupts entire structure | Convert only real ZIP files, not other archives | | Keeping backup files inside (e.g., script.js~ ) | Causes JSON parsing errors | Delete all hidden files before zipping | | Zipping the parent folder | Creates ProjectFolder/project.json → Scratch sees no root JSON | cd into the folder, then zip contents | | Using online converters | Uploads your assets to unknown servers + often re-samples images to 72dpi | Use offline tools only |
Ensure your project.json file is encoded in without a Byte Order Mark (BOM). Improper text encoding can cause the Scratch engine to misread asset paths, leading to broken images or silent audio tracks upon conversion. Troubleshooting Common Conversion Errors
Before converting, ensure your ZIP archive contains:
This manual method ensures complete control over the compression process and file structure, which is essential for maintaining "extra quality."
If you are seeing a when uploading to Scratch?
: You can manually access a project's assets by changing the file extension from .sb3 to .zip and extracting the contents.