Do you need to migrate assets to a different project that uses an older Unreal Engine version ?

Have you migrated assets to an earlier version of the Unreal Engine and they don’t seem to “appear” in the content browser ?

Do you want to make your assets available to people using earlier versions of Unreal Engine ?

 

Then what you need is to use the Asset Downgrader to downgrade those assets to the specific version you want.

 

Asset Downgrader will downgrade assets to 5.5.4, 5.4.4, 5.3.2, 5.2.1, 5.1.1, 5.0.3, 4.27, 4.26 . It works by first upgrading the assets to Source Version (5.3-5.6), and then applying various patches to the .uasset files in order to make them compatible with the TargetVersion, just without the newer data (i.e. nanite data is removed for a 4.27 downgrade). Do note that features of the newer unreal versions (like nanite on masked materials, new material nodes, new niagara modules) can’t be ported to the old versions.

 

Video Tutorial and Demo

 

How it works :

• First, backup all your assets as this plugin is highly experimental and in certain situations it may corrupt assets or crash the editor if something goes wrong.

• Either have 2 projects, one the SourceVersion and the other with the TargetVersion, or just switch versions for the project you’re working with. Integrate the plugin in both projects.

• In the SourceVersion project, select the assets you wish to downgrade.

• From the Downgrader menu choose DowngradeSelectedAssets.

• Migrate the assets by copy pasting the .uassets . Do not use Unreal’s Actions->Migrate… because that will resave assets in the SourceVersion format. Alternatively, switch the version of the project to the TargetVersion

• If TargetVersion is a 5.0.3 project add

[Core.System]

UsePackageTrailer=True

to Config/DefaultEngine.ini

You will get a crash on opening assets in 5.0.3 if this is not enabled.

• On the TargetVersion project add the google drive version of the plugin for that specific target version
• Open the TargetVersion project and then the downgraded assets. If there were no errors, the assets should open correctly. Certain assets, in order to be migrated to other TargetVersion projects that don’t have the Downgrader plugin, need to be resaved through the plugin ( select all the assets and use the plugin’s SaveSelectedAssets option ) inside the TargetVersion editor.

 

Supported Assets Spreadsheet

 

In order to downgrade certain assets (or all assets as it’s the case for 5.4) you need to use a custom version of unreal engine that has specific engine modifications in order to make downgrading possible. Check the plugin folder ( UE_5.5\Engine\Plugins\Marketplace\AssetDowngrader\Download Custom Engine & Plugin.url) for the link to where you must download both a custom UE5.5 build and a precompiled version of the plugin for this engine version. After downloading the custom engine and integrating the precompiled plugin in the source project’s plugins folder you need to switch the source project engine version to this custom engine build. The video tutorial shows this entire process. Also, if you require an older custom engine build like 5.3 do remember that upgrading assets to the latest version is always possible and I always recommend using the latest custom engine build because that’s the only one in active development. If that’s not feasible for you, please contact me to discuss alternatives.

 

Can it be downgraded lower than 4.26 ?

Not currently but with enough research & engine modifications definitely possible. Contact me if you have specific needs.

 

My asset is not supported, can you add support ?

Let me know what kind of assets you’re interested. Any asset is implementable but it requires a lot of work.

 

Known Issues:

• if for any reason you get a crash with the launcher version of the plugin, please use the Downgrader Custom Engine along with its own version of the plugin

– If assets don’t appear in packaged builds you forgot to resave the assets ( use the plugin’s SaveSelectedAssets option )

– some downgraded scenes’ lighting may look too bright in 5.0. You may need to tune ReflectionProbes/Skylight/Directional light intensity and/or rebuild lighting

– if downgrading entire projects, a lot of assets will be loaded into memory, so you may need a lot of RAM sometimes up to 128GB

– if encountering unknown startup crashes due do downgrading a lot of assets, try and downgrade assets one by one, or exclude/delete the offending asset.

– textures with formats like RGBA32F are not downgraded past specific versions like 5.0 because those formats don’t exist in 5.0.

– opening certain maps will sometimes crash. This might be due to masked materials with nanite which are not allowed in 5.0. Try first to open assets individually or remove nanite entirely and then open the map

– if landscapes are pure black in 4.27 then use the Downgrader menu option FixLandscape

• Skeletal meshes can crash when saved in 4.27 if their binary format was not in the 5.4+ format originally. To prevent crashes first save the skeletal mesh so the binary format gets updated. If you have plenty of them use the plugin’s SaveSelectedAssets prior to downgrading.

 

If you use your own custom build of unreal and require the engine modifications to downgrade, I can provide this service for a fee. Contact me for licensing details.

 

If you have any issues, errors or crashes don’t hesitate to contact me at [email protected] as this plugin is highly experimental ( Please include the offending uasset/project as well )