An .sb3 file is Scratch’s native project format, introduced with Scratch 3.0 in 2019. Despite its custom extension, containing JSON data, assets (costumes, sounds), and metadata.
Converting a file to an SB3 format is essentially just a matter of renaming the file extension , as SB3 files are actually compressed ZIP archives containing Scratch 3.0 project data. Why Convert ZIP to SB3?
: The brain of the project. This text file contains all the code, blocks, variables, and structural data for your sprites.
A standard data compression archive that contains one or more files or folders to reduce file size and make transferring easier.
While converting ZIP to SB3 is technically safe, you must be cautious about you get your ZIP files. convert zip to sb3
Because the internal structure is identical, converting a ZIP to an SB3 does not require complex file conversion software. It simply requires changing how your operating system reads the file container. Method 1: The Rename Trick (Fastest Method)
Beyond simple conversion, understanding the ZIP-based nature of SB3 files opens up a world of possibilities for developers and advanced users. Because you can access the raw JSON and assets, you can build powerful tools that interact with Scratch projects programmatically.
Highlight every single item inside the folder (Ctrl+A on Windows, Cmd+A on Mac). Do not select the parent folder itself; select the contents. Compress to ZIP:
Why? Because an SB3 file can contain JavaScript inside project.json (via "extension" blocks). A malicious actor could theoretically embed harmful code that exploits an old version of the Scratch app. Always scan ZIP files with an antivirus before renaming them to SB3. Why Convert ZIP to SB3
⚠️ – SB3 expects the JSON and assets at the root of the archive.
: A collection of SVG, PNG, WAV, and MP3 files. These are the costumes, backgrounds, and sounds used in your project. They are usually named with long strings of numbers and letters (MD5 hashes).
Note: You cannot simply rename a ZIP to SB3 if you have extracted the folder. The folder must be recompressed into a ZIP file first, then renamed.
To convert the extracted files to an SB3 file, you can use the scratch command: A standard data compression archive that contains one
Crucial Rule: Do not zip the parent folder. You must zip the contents inside the folder.
: The core file containing all the blocks, variables, and project logic. Asset Files files named with hexadecimal strings (e.g., cd21...svg ) that represent the costumes and sounds. Troubleshooting & Tools File Extensions Not Visible : If you don't see the
If your file was originally an .sb3 project that was renamed to a .zip (or compressed directly from Scratch assets), you can convert it instantly by changing the extension. On Windows: Open and locate your .zip file.
Method 2: Compressing Assets Manually (For Extracted Folders)