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Question about exporting Spine 4.3 projects for use in Spine 4.2

Steven

Hello,

I have a question regarding version compatibility between Spine 4.3 and Spine 4.2.

If an animation project is created and saved in Spine 4.3, is it possible to export or convert it in a way that allows it to be opened or used in Spine 4.2?
For example, is there any supported workflow such as exporting with backward compatibility, or is the version difference fundamentally not supported?

I understand that newer Spine versions may introduce features that are not available in older versions, but I wanted to confirm whether there is any officially recommended approach for this case.

Thank you very much for your time and support.

Best regards,

Misaki

Steven Spinebot's answer is correct. While there is a method to downgrade skeleton data to 4.2 in cases like accidentally upgrading to 4.3, incorporating this into your regular workflow is never recommended. There is no guarantee the same animations will be reproduced.
If you want to use the 4.3 editor, upgrade your project's runtime to 4.3 and use that.

Spinebot

Hello!

Thank you for your question about version compatibility between Spine 4.3 and 4.2.

Backward Compatibility Limitations

Spine project files are backward compatible (newer versions can open older files) but not forward compatible (older versions cannot open newer files). Once a project is saved in Spine 4.3, it cannot be directly opened in Spine 4.2.

Possible Workaround

There is a workaround you can try, though it may result in data loss:

In Spine 4.3, use JSON export and set the Version to 4.2
Run Spine 4.2 and use data import to bring the JSON data into the editor
If the project looks OK, save it as a Spine 4.2 project file

Important Considerations

This approach may result in data loss if Spine 4.3 features that don't exist in 4.2 were used in your project
For example, any new animation curves, constraints, or features introduced in 4.3 may be lost or converted incorrectly
This method is intended as a last resort to recover work, not as a regular workflow

Best Practice

The recommended approach is to ensure version synchronization from the start - meaning if you need to work with Spine 4.2, create your projects in Spine 4.2 rather than a newer version.

I hope this helps clarify the situation!

Steven

Misaki
In our project, we initially created and received the animation files using the Spine 4.3 editor, as the project was planned to use Spine 4.3. However, due to project requirements, we later found that we also need to support Spine 4.2.

We tried exporting the data from Spine 4.3 and importing it into Spine 4.2.
As a result, only the skeleton and skins were imported successfully, but all animations were missing.

At this point, I would like to ask:
• Is there any supported or recommended way to preserve animations when moving data from Spine 4.3 to Spine 4.2?
• Or is this limitation expected, meaning that converting animation data from 4.3 to 4.2 is fundamentally not supported?

If there is no possible workaround, we would like to confirm that clearly so we can adjust our pipeline accordingly.

Misaki

Steven Unfortunately, without seeing your actual Spine project, I cannot say for certain why all animations were lost. However, when exporting Spineboy using version 4.3.39-beta to JSON with the Version option set to 4.2, and then importing it into 4.2.43, all animations import correctly. Therefore, unless you are actively using features introduced in the 4.3 beta, it is highly unlikely that all animations would be lost.

As we can only speculate about the cause based on text exchanges alone, if you would like us to investigate further, please email us a Spine project file that reproduces the issue via email: contact@esotericsoftware.com

Steven

Misaki
When exporting from Spine 4.3, we used the binary format instead of JSON for project optimization.
Could this be the reason why the animations are missing when importing into Spine 4.2?

Misaki

Steven Yes, when you want to downgrade your Spine project, you must export the skeleton data in JSON format. You cannot downgrade versions using skeleton data exported in binary format. The correct procedure for downgrading is as explained in the "Possible Workaround" section in Spinebot's answer:

In Spine 4.3, use JSON export and set the Version to 4.2
Run Spine 4.2 and use data import to bring the JSON data into the editor
If the project looks OK, save it as a Spine 4.2 project file

Steven

Misaki
Thank you very much for your kind and detailed explanation.
I will try exporting again using this approach and will check the results.

sunwangshu

Kind of related, just found a workaround if your goal is to export to json and 4.2 and use in Unity. We had spines created in 4.2 iirc, but later slightly modified and saved in 4.3. Our goal is to export them to work correctly with Unity runtime 4.2, instead of recovering the spine project in 4.2.
Anyways, below are the steps:

export with version 4.2. If you import directly from this step, unity spine runtime 4.2 would complain something about version string.
open the json file, in the beginning of the file, the version line would be something like "spine":"4.2-from-4.3.23". This is the line that the importer complains about.
change that line into "spine":"4.2.43", and save the json
import in Unity. Now it imports correctly in Unity.

Somehow it worked for me. Maybe we only did minimal edits and didn't touch some new features in 4.3. Anyways, use at your own risk.

Misaki

sunwangshu In fact, compared to the binary format, the JSON format tends to retain generally the same structure even after minor version updates, so such a workaround might be effective. However, this is not the method we recommend, and there is a possibility that issues that were difficult to detect initially may be discovered later on. It is safest to always use skeleton data exported from a version of the Spine Editor that matches the runtime used in your project.

sunwangshu

Misaki Thanks and noted. Was able to finally downgrade the spine project file to 4.2 following the steps from the spine bot. The step that got me stuck is somehow the images all appear missing. Was fixed by reassigning the relative path for the images root.