What Is .sb3 file

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Last updated: April 11, 2026

Quick Answer: A .sb3 file is a project file created by Scratch 3.0, MIT's visual programming platform introduced in January 2019. These files contain complete Scratch projects including sprites, scripts, sounds, images, and metadata in a ZIP-based JSON structure. .sb3 files are the standard format for saving and sharing interactive projects built with Scratch 3.0 and newer versions.

Key Facts

Scratch 3.0 released January 2, 2019, introducing .sb3 format to replace older .sb2 files from Scratch 2.0
Over 100 million projects have been created in Scratch, with millions of .sb3 files actively shared on the platform
.sb3 files use ZIP compression containing JSON files that define sprites, scripts, sounds, costumes, and project structure
Scratch reaches over 7 million monthly active users, predominantly students ages 6-16 learning programming fundamentals
.sb3 files can be created, edited, and shared free at scratch.mit.edu or through Scratch offline editor for desktop

Overview

A .sb3 file is the standard project file format for Scratch 3.0, MIT Media Lab's visual programming language designed for educational purposes. Introduced on January 2, 2019, .sb3 replaced the older .sb2 format, providing enhanced compatibility and improved project structure for millions of young programmers worldwide.

These files serve as complete containers for interactive projects, combining executable scripts, visual assets, audio files, and metadata into a single portable package. Users can create, edit, share, and remix .sb3 projects directly on the Scratch website (scratch.mit.edu) or using the Scratch offline editor, making programming accessible to learners without coding experience.

How It Works

The .sb3 file format functions as a sophisticated yet accessible package structure:

ZIP-Based Container: Each .sb3 file is technically a compressed ZIP archive that can be extracted to reveal its internal JSON structure and asset files, allowing developers to inspect and understand project composition.
JSON Project Definition: The core file (project.json) contains metadata about the project including name, creator, version information, and a complete description of all scripts, blocks, and logical flow using JSON data structure.
Sprite and Costume Management: All visual elements including sprites (characters), costumes (sprite appearances), and backgrounds are stored as individual image files organized within the ZIP archive with corresponding JSON references.
Sound and Audio Storage: Audio files for background music, sound effects, and voice recordings are embedded as separate files within the container, referenced by the project scripts and event handlers.
Script Synchronization: Scratch scripts composed of visual code blocks are serialized into JSON format, preserving block connections, parameters, variables, and execution order for perfect project replication.

Key Comparisons

Aspect	.sb3 Format	.sb2 Format (Scratch 2.0)	Other Languages (.py, .java)
Year Introduced	January 2019	May 2013	Varies by language
Structure	ZIP-based JSON with assets	ZIP-based ActionScript	Plain text source code
Visual vs Text	Block-based visual programming	Block-based visual programming	Text-based syntax required
Learning Curve	Beginner-friendly (ages 6+)	Beginner-friendly (ages 8+)	Requires coding knowledge
Asset Embedding	Native image, sound, sprite storage	Asset embedded in binary format	Separate media files needed

Why It Matters

Educational Foundation: The .sb3 format democratizes programming education by enabling over 7 million monthly active users to create interactive games, animations, and stories without traditional coding knowledge, supporting UNESCO's digital literacy initiatives.
Accessibility and Portability: .sb3 files can be easily shared, remixed, and collaborated on across the Scratch platform, allowing teachers to distribute lessons and students to contribute to collective learning projects globally.
Creative Expression: By combining visual programming with embedded media, .sb3 files empower learners to develop computational thinking while creating personally meaningful projects that integrate art, music, and storytelling.

The .sb3 file format represents a critical evolution in computer science education, bridging the gap between abstract coding concepts and tangible creative output. Since its introduction in 2019, over 100 million Scratch projects demonstrate how accessible file formats can transform technology education. Educational institutions worldwide have adopted .sb3 projects as core curriculum components, with teachers creating thousands of lesson plans using the format. The ability to save, share, and iterate on .sb3 files has created a vibrant community where young learners build on each other's work, fostering collaboration and computational thinking skills essential for the digital future.