Now, a week later, with the science fair submission portal open and his teacher, Ms. Okonkwo, waiting for the link, Leo double-clicked the file. It unzipped neatly, revealing a folder full of assets: costumes, sounds, project.json . All the organs of his digital creature, laid out on a slab. But a Scratch project isn’t a folder. It’s a single, secretive little package with the .sb3 extension. And Leo’s browser had wrapped it in a postal envelope called ZIP.
If the .zip file is corrupted, you need to extract the contents and re-compress them.
He saved the result as QuantumKitten_FIXED.sb3 .
He hadn't used the Scratch editor’s "Save to your computer" function. He had just... zipped the raw assets.
is a compressed folder used to store multiple items together. convert zip to sb3 fix
Unzip your file and look inside. Ensure that project.json and all asset folders are sitting in the root directory of the folder. Select the individual files themselves (not the parent folder), right-click, and compress them into a new ZIP archive. Then, rename that archive to .sb3 . Fix 2: Broken or Unsupported Asset Formats
If the manual conversion fails, the underlying zip structure may be damaged. In such cases: Third-Party Repair : Tools like BetterZip or Archiver
: The assets are named using long strings of numbers and letters (their MD5 hashes) instead of names like "cat.png".
: Open your ZIP file. If you see a single folder inside it, open that folder. Select the actual files ( project.json , etc.), right-click them, and compress those specific items directly. Fix 2: Missing project.json Now, a week later, with the science fair
Panic set in. He tried the obvious: he renamed QuantumKitten.zip to QuantumKitten.sb3 . The icon changed. Hope flickered. He dragged it into the Scratch editor.
Defeated, Leo slumped back. The deadline was in four hours. He was about to type a humiliating email to Ms. Okonkwo when a memory surfaced: a late-night coding forum, deep in the archives, where a user named had posted a cryptic one-line reply to a similar lament.
A downloaded project from the Scratch website arrives as a .zip file instead of .sb3 .
To turn a ZIP folder back into a working Scratch project, follow these precise steps to avoid corruption. Step 1: Check the Internal Structure All the organs of his digital creature, laid out on a slab
Confirm the change when your operating system warns you about changing file extensions. Step 3: Extract and Inspect the Files
The newly downloaded .sb3 file will automatically feature clean, standardized formatting that successfully loads into the official Scratch editor.
Delete .zip at the end of the filename and type .sb3 .
Go to the Scratch Editor , click File > Load from your computer , and select your new file. Method 2: Manual Re-Zipping (The "Broken Archive" Fix)
Ensure the tool does not alter the underlying project.json formatting.
This is the most common error. It almost always points to a problem with the project.json file.