Convert SB3 to HTML

A browser, website, or offline kiosk may require a Scratch project as a playable HTML file instead of an .sb3 download. Packaging the project as HTML lets recipients run it without opening the Scratch editor, while preserving the original SB3 file for future editing.

What the SB3 format is

SB3 is the Scratch 3 project format used by Scratch and compatible editors such as TurboWarp. An SB3 file is a ZIP archive containing project.json, sprites, costumes, sounds, scripts, and other project assets.

Scratch creates an SB3 file through File → Save to your computer. Projects downloaded from Scratch, moved between computers, or imported into a compatible editor normally use this format. Renaming .sb3 to .html does not convert the file; a browser cannot execute the Scratch project structure without a JavaScript runtime.

What the HTML format is

HTML is the document format interpreted by web browsers. For a Scratch project, the useful result is a packaged HTML application containing, or loading, a JavaScript Scratch-compatible runtime and the project assets.

The result can be shared as a webpage, embedded in a site, or opened for offline playback. It is not a conversion of Scratch blocks into ordinary HTML elements such as paragraphs and headings; the block logic remains data interpreted by the runtime.

How to convert SB3 to HTML

TurboWarp Packager is the most practical option for producing a browser-playable HTML file. Its online version is available at packager.turbowarp.org, and its desktop version is suitable when the project should not be uploaded to a third-party service.

1. Keep an untouched copy of the original .sb3 file.
2. Open TurboWarp Packager and select the option to upload or choose a project.
3. Select the SB3 file from your computer.
4. Review the available settings, including fullscreen behavior, controls, player loading, and whether project data is embedded. Setting names vary by version.
5. Choose the HTML output and download the generated .html file.
6. Open the file in a current browser such as Chrome, Firefox, Edge, or Safari, then test scripts, sprites, sounds, keyboard controls, and any save features.

The online packager is convenient when uploading the project is acceptable. Use the desktop packager for private, large, or sensitive projects. Generic file-converter sites generally cannot perform this conversion: they may only rename the file or extract its ZIP contents, without adding the runtime required to execute Scratch blocks.

Quality and compatibility limitations

The generated HTML is a packaged application, not an editable Scratch project. Retain the SB3 file if the blocks, costumes, sounds, or project structure must later be changed; reopen that file in Scratch or TurboWarp.

Test the packaged project because behavior may differ from the Scratch website. Extensions, cloud variables, online services, microphone and camera access, browser security policies, and device-specific features may require network access, user permission, or TurboWarp-specific support. Cloud variables and other Scratch server features may not work when the HTML file is opened locally.

A self-contained HTML file can be large because it includes the runtime and project assets. If the packager offers external assets or a ZIP package, use that option for distribution only when every generated asset is kept with the HTML file; some browsers also restrict local-file access to external resources. JavaScript must be enabled for the packaged project to run.