Zip To Sb3 Extra Quality – Direct Link

#!/bin/bash
for zipfile in *.zip; do
    base=$(basename "$zipfile" .zip)
    mkdir "$base"_temp
    unzip -q "$zipfile" -d "$base"_temp
    cd "$base"_temp
    zip -q -X -0 -r "../$base.sb3" *
    cd ..
    rm -rf "$base"_temp
done

This loop preserves extra quality by using no compression (-0) and stripping metadata (-X).

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This is the secret to extra quality. Most ZIP tools use DEFLATE compression (level 6). But for SB3, you need:

How to do it in 7-Zip:

Why “Fastest” = Extra Quality?
Because slower compression (Ultra) re-encodes PNG chunks and can alter audio headers. For SB3, faster compression preserves binary integrity.

Before distribution:

If you are building this from scratch to maximize quality, follow these rules before zipping:

1. Vector vs. Bitmap:

2. Audio Fidelity:

| Tool | Best for | Quality retention | |------|----------|-------------------| | 7-Zip + manual rezip | Individual projects | Perfect | | Scratch Tools (Python CLI) | Batch conversion + JSON repair | Very high | | TurboWarp Packager (export as SB3) | Projects from HTML or ZIP | High (sanitizes JSON) | | sb3-utils npm package | Developers merging assets | Perfect (preserves all metadata) | zip to sb3 extra quality

If you're working directly with SB3 files:

Converting a ZIP to an SB3 file should be a trivial task. Yet, due to poor tooling and misunderstood file formats, many creators lose hours fixing corrupted sprites and muffled audio.

By demanding extra quality—using manual Store compression, avoiding transcoding, and validating JSON integrity—you preserve the creator’s original intent. Whether you are a teacher preparing classroom materials or a modder building the next hit platformer, these techniques will keep your assets crisp, your audio pristine, and your extensions functional.

Next Steps:

Now go forth and convert—without compromise.

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Call to Action: Have you encountered a ZIP-to-SB3 quality loss horror story? Comment below or join the Scratch forums discussion on preserving asset fidelity.

Scratch supports .mp3 (CBR, 128kbps or higher) and .wav. For extra quality:

Workflow:

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