Have you ever tried to upload a Scratch project only to get a loading error, or did your .sb3 file mysteriously turn into a .zip archive? Scratch 3.0 files are actually compressed ZIP folders containing all the code, assets, and sounds of your project. If the file extension changes or the internal structure breaks, Scratch cannot read it.
Open a browser and go to a free online tool like or any JSON validator. Paste your code into the validator and click Validate JSON .
Your operating system is hiding known file extensions. When you renamed the file to project.sb3 , the computer actually named it project.sb3.zip , keeping it a ZIP file. convert zip to sb3 fix
: Scratch expects assets (like .svg or .wav files) to have specific MD5-based filenames that match the references in your project.json . If you manually renamed these files, the project will break. Specialized Tools
“The fix is in the first 18 bytes. Strip the extra folder. The sb3 is a zip of the zip.” Have you ever tried to upload a Scratch
You can use sb3fix from Node.js like this:
On : Select all files, right-click, choose Compress to ZIP file . Open a browser and go to a free
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Sometimes, high-level compression methods (like Ultra or 7z-specific formats) confuse the Scratch parser.
Extract the ZIP completely. Right-click > Extract All . Step 2: Open the extracted folder. Look for a file named project.json .
How to Convert ZIP to SB3 (and Fix Common Errors) Scratch 3.0 projects use the .sb3 file format to store animations, games, and code. Under the hood, an .sb3 file is actually just a compressed archive containing JSON code, costumes, and sounds.