Ensure file extensions are visible. Click the tab at the top, click Show , and check File extensions . Right-click your file and select Rename (or press F2 ).

Method 2: Re-Archiving Loose Scratch Assets (The Safe Method)

If you're a developer looking to create or export .sb3 files programmatically, the @mbw/sb3 package (available on JSR) provides robust abstractions for working with Scratch project files. This package, which is built and signed on GitHub Actions, works with Bun and Deno, making it a great choice for modern JavaScript/TypeScript projects.

Select the items inside this folder simultaneously (press Ctrl + A on Windows or Cmd + A on Mac). Right-click the highlighted files:

Before converting, it helps to understand what happens under the hood. An .sb3 file is structurally identical to a standard .zip file. It contains:

Ultimately, the ZIP-to-SB3 pipeline represents the open nature of the Scratch platform. By leveraging standard compression formats, Scratch ensures that creativity is not locked behind proprietary walls, allowing anyone with a basic understanding of file structures to update, modify, and enhance their digital creations. json file inside these archives?

An .sb3 file is a compressed archive containing all the assets of a Scratch 3.0 project. If you change the extension of any .sb3 file to .zip and unzip it, you will find: