scratch3.xml

<?xml version="1.0" encoding="utf-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
<!--
Scratch file associations and mimetypes

Only .sb3, .sprite3, .sb, and .sprite have documented mimetypes from the upstream.
The .sb2 and .sprite2 does not have any mentioned mimetype but it is treated as x-scratch-project by the upstream.

application/x.scratch.sb3
https://github.com/scratchfoundation/scratch-editor/blob/441b69ed787cf223d7e240cfc7573875f8a9a2bd/packages/scratch-vm/src/virtual-machine.js#L405
https://github.com/scratchfoundation/scratch-desktop/blob/dd3e8ef47a924f80a75e1e24396a0c0bdf3b54e4/src/main/index.js#L281

application/x.scratch.sprite3
https://github.com/scratchfoundation/scratch-editor/blob/441b69ed787cf223d7e240cfc7573875f8a9a2bd/packages/scratch-vm/src/virtual-machine.js#L454

application/x-scratch-project (both .sb, .sprite, and Scratch 2 files customarily)
https://github.com/scratchfoundation/Scratch_1.4/blob/d26f099e3d8358760d0129de4a57e792d97d146f/src/scratch.xml#L3
https://github.com/scratchfoundation/Scratch_1.4/blob/d26f099e3d8358760d0129de4a57e792d97d146f/src/scratch.desktop#L9
-->
  <mime-type type="application/x-scratch-project">
    <sub-class-of type="application/octet-stream"/>
    <comment>Legacy Scratch File</comment>
    <generic-icon name="scratch3"/>
    <glob pattern="*.sb"/>
    <glob pattern="*.sb2"/>
    <glob pattern="*.sprite"/>
    <glob pattern="*.sprite2"/>
  </mime-type>
  <mime-type type="application/x.scratch.sb3">
    <sub-class-of type="application/zip"/>
    <comment>Scratch 3 Project</comment>
    <generic-icon name="scratch3"/>
    <glob pattern="*.sb3"/>
  </mime-type>
  <mime-type type="application/x.scratch.sprite3">
    <sub-class-of type="application/zip"/>
    <comment>Scratch 3 Sprite</comment>
    <generic-icon name="scratch3"/>
    <glob pattern="*.sprite3"/>
  </mime-type>
</mime-info>