: The main data file must be named exactly project.json in lowercase letters.
If you are a Scratch programmer, educator, or parent, you have likely encountered a frustrating roadblock: you download what you think is a Scratch project file (usually a .sb or .sb2 file), but instead, your computer saves it as a compressed .zip folder. When you try to open this ZIP file in the Scratch editor (whether offline or online), you are met with an error message or a jumble of confusing asset files.
As of 2026, the tools and methods outlined in this guide represent the most up-to-date approaches for ZIP to SB3 conversion. The core principle remains simple: SB3 files are ZIP archives at heart. By understanding this relationship, you can confidently convert between formats, extract project assets, and manipulate Scratch projects with ease. convert zip to sb3 updated
SB3, on the other hand, is a file format used by Scratch, a popular programming language and online community developed by MIT. SB3 files are used to store Scratch projects, which can include sprites, scripts, and other project data.
: Ensure your file isn't accidentally named project.sb3.zip . Double-check your operating system's visibility settings to see the true extension. : The main data file must be named exactly project
If you need a script or tool to do this in bulk or programmatically, let me know your operating system.
Because an .sb3 file is actually just a renamed ZIP archive, converting between the two formats is incredibly simple. This updated guide covers the fastest, safest methods to convert your ZIP files back into working SB3 projects. Understanding SB3 and ZIP Files As of 2026, the tools and methods outlined
If Scratch gives you an error when opening the file, the ZIP folder may have been corrupted during download. Try re-downloading the original source file.
If Scratch refuses to open your converted SB3 file, the problem is usually how the file was zipped. Ensure that project.json is at the root level of the ZIP archive and not tucked inside another folder. The file still says .sb3.zip
Not every ZIP file can be successfully converted to an SB3 file. A valid Scratch project ZIP must contain a project.json file and corresponding media assets structured correctly. Without these components, the resulting .sb3 file won't open properly in Scratch.