Convert Zip To Sb3 Fix «2025-2026»

| Error Message | What It Means | The Fix | | :--- | :--- | :--- | | "Not a valid Scratch 3 project" | The file lacks project.json at the root level. | Use Method 2 above to re-zip only the inner contents, not the folder. | | "File size too large" | You have an HD video or hundreds of assets inside. | Convert large WAVs to MP3 (64kbps) and large PNGs to JPEG before re-zipping. | | Scratch crashes on load | Corrupt asset inside the ZIP (e.g., a damaged image). | Extract the ZIP, delete the newest asset you added, then re-zip as SB3. | | "Sprite missing" | The ZIP contains files, but the project.json references missing files. | Re-extract and ensure every image listed in the JSON is physically present. |

If Scratch fails to open, unzip the archive into a folder and inspect structure:

Validate project.json:

Confirm asset filenames and paths:

Re-zip correctly:

Test open in Scratch.

If you downloaded a project and it ended up as a .zip file, or if Scratch refuses to open your .sb3 file, follow these steps. convert zip to sb3 fix