Used unsupported compression algorithm (e.g., 7z or RAR renamed to SB3).
Scratch supports and MP3 (up to 320kbps). Standard converters often downsample to 128kbps. Extra quality preserves the original bitrate.
: After making changes, select all files inside the project folder (not the folder itself), compress them into a new ZIP, and rename that ZIP to .sb3 . Achieving "Extra Quality" and Optimization zip to sb3 extra quality
Converting ZIP to SB3: How to Convert Your Scratch Files with Maximum Quality
The project.json file must be encoded in strict UTF-8 without a Byte Order Mark (BOM). Incorrect text encoding will result in the notorious "Could not load project" error when importing to Scratch. Step-by-Step Manual Conversion Method Used unsupported compression algorithm (e
If Scratch refuses to open your converted file, the most common culprit is nested folders. The project.json file must sit at the absolute root of the ZIP structure. If you zip a folder that contains the files, Scratch will fail to read it. Always select the files directly inside the directory when compressing. Missing Costumes or Sounds
By understanding that an SB3 file is a specialized archive, you can avoid shady online converters that ruin project quality. Stick to manual renaming or lossless packagers to keep your projects looking sharp and sounding clear. Extra quality preserves the original bitrate
Scratch identifies assets using their MD5 cryptographic hash followed by the file extension. Inside a high-quality SB3 file, you will rarely see a file named cat.png . Instead, it will look like this: b787fbdcd92bb06ec9f9da7b0dcfc69b.png 2. Flat Directory Structure
The Scratch community is pushing for a formal . Proposed features include:
This comprehensive guide covers how to convert , ensuring asset optimization, correct project structure, and flawless compatibility. Understanding the Internal Anatomy of an SB3 File