Convert SB3 to SB2

A legacy Scratch 2 Offline Editor, older classroom computer image, or archive workflow may require an .sb2 project and cannot open an .sb3 file. Scratch 3 can import many Scratch 2 projects, but it has no supported command to export projects back to Scratch 2.

SB3 and SB2 project formats

An .sb3 file is a Scratch 3 project produced by the Scratch website, Scratch Desktop, TurboWarp, and compatible Scratch 3 editors. It is a ZIP-based package containing a Scratch 3 project.json file, sprites, costumes, backdrops, sounds, variables, lists, scripts, and extension-related project data.

An .sb2 file is a Scratch 2 project used by the discontinued Scratch 2 online editor and Scratch 2 Offline Editor. It is also a ZIP-based package, but it uses a different project.json schema, block representation, and asset references.

The practical advantage of .sb2 is compatibility with software that is limited to Scratch 2. It is not inherently smaller or more capable than .sb3, and renaming project.sb3 to project.sb2 does not convert it.

Convert an SB3 project

For simple projects, use the open-source SheepTester SB3-to-SB2 converter. Its source code is available through the linked GitHub project, and the hosted converter processes the selected project in the browser.

1. Keep an unchanged copy of the original .sb3 file.
2. Open the converter, select the .sb3 file, and download the generated .sb2 file.
3. Open the result in the exact Scratch 2 environment that must use it.
4. Test every green-flag script, key and mouse interaction, broadcast, variable, list, clone, costume change, sound, and sensor input.

The converter can translate many standard Scratch blocks, but it cannot guarantee a working result for every project. Do not upload unpublished school, client, or personal work to unknown conversion sites; use an identifiable service with published source or a clear privacy policy.

For projects that fail automated conversion, rebuild them in the legacy Scratch 2 Offline Editor. Open the source in Scratch Desktop or the Scratch website, export individual costumes and sounds, then import them into Scratch 2 and recreate sprites, variables, lists, broadcasts, custom blocks, and scripts. Save through File → Save to your computer to create a genuine .sb2 file.

Scratch 2 Offline Editor depends on its legacy Adobe AIR-based runtime and may require an older or specially maintained operating-system environment. Test the finished file in the target installation rather than assuming that a file accepted by another Scratch 2 setup will behave identically.

Compatibility limits

Automated downgrade requires translation between incompatible project schemas; it is not a ZIP repackaging operation. Block opcodes, script structure, asset metadata, comments, monitors, and extension data must be rewritten for Scratch 2.

Scratch 3-only blocks and extensions may be removed, translated imperfectly, or require redesign. Text to Speech, Translate, newer LEGO integrations, micro:bit support, and other hardware-dependent features need particular checking; some Scratch 3 extensions have no usable Scratch 2 equivalent, while others depend on different extension software or hardware support.

Projects using standard motion, looks, sound, events, control, sensing, operators, variables, lists, pen, custom blocks, and basic cloning are the strongest candidates for conversion. Check timing and execution order after conversion, especially around wait blocks, sound playback, clone creation, broadcasts, and sensor values.

Do not unzip an .sb3 project and edit or rename its internal project.json file. Scratch 2 expects Scratch 2 script and asset structures and will reject or misread Scratch 3 project data.