Cache Management

Unreal caches aggressively. That is what makes iteration bearable, but it also means a stale cache can make a correct change appear not to work — or an incorrect one appear to.

What the script clears

WipeShaderCache.bat deletes three directories relative to the engine root:

Directory	Contents
`Engine\DerivedDataCache`	Compiled shaders, cooked textures, built meshes and every other derived artefact
`Engine\Intermediate\Shaders`	Intermediate shader compilation output
`Engine\Saved\ShaderDebugInfo`	Shader debug symbols and preprocessed source dumps

It reports each directory as deleted, not found, or failed. A failure almost always means something still holds a file handle.

After wiping, the next editor launch recompiles everything it needs. On a large project this can be tens of minutes or more. Do not do it casually.

When to wipe

You changed a .usf or .ush file and nothing happened: Shader source changes are usually picked up, but engine-level global shader changes sometimes are not. Try recompileshaders global or recompileshaders changed in the console first — it is far faster than a full wipe.
You changed a compile-time switch: Changing VITE_RT_PSO_DEBLOAT, VITE_O_SSAO or any other VITE_* switch changes which shader permutations exist. The engine rebuild handles the C++, but cached shaders from the old configuration can linger. Wipe after switching.
You pulled engine changes that touched the renderer: A merge that changes shader code or the shader map keying can leave a cache the engine misreads.
You are getting shader compilation errors that do not match the source: A classic stale-cache symptom: the reported error line does not exist in the file you are looking at.
The editor crashes on startup after an engine change: Worth trying before deeper investigation, since it is cheap to rule out.

When not to wipe

Wiping the DDC is a heavy hammer and is frequently applied to problems it cannot solve.

Project-level problems. The script clears the engine DDC. Your project has its own DerivedDataCache folder and its own Intermediate and Saved directories. Engine-level wiping does not touch them.
Runtime rendering bugs. If an effect renders wrongly but consistently, that is a code or configuration problem, not a cache problem. Check the compile-time switch availability table first — many ray tracing features are compiled out by default and their console variables silently do nothing.
Long shader compile times. Wiping makes this worse, not better. See Shader Compilation and PSO.

Lighter-weight alternatives

Try these before a full wipe:

Approach	Clears	Cost
`recompileshaders changed`	Modified shaders only	Seconds
`recompileshaders global`	Global shaders	Under a minute
`recompileshaders material <name>`	One material	Seconds
Delete the project's `Intermediate\`	Project build intermediates	Project rebuild
Delete `Engine\Intermediate\Shaders` only	Intermediate shader output, keeping the DDC	Partial recompile

The last one is worth knowing: the DDC is the expensive part to rebuild. If you only need to clear intermediate shader state, deleting that one directory by hand is much cheaper than running the full script.

Cache locations

Cache	Path	Cleared by the script
Engine DDC	`Engine\DerivedDataCache`	Yes
Engine intermediate shaders	`Engine\Intermediate\Shaders`	Yes
Shader debug info	`Engine\Saved\ShaderDebugInfo`	Yes
Project DDC	`<Project>\DerivedDataCache`	No
Project intermediates	`<Project>\Intermediate`	No
Shared / network DDC	Per `BaseEngine.ini` DDC configuration	No
Local user DDC	`%LOCALAPPDATA%\UnrealEngine\Common\DerivedDataCache`	No

Disk footprint

The engine DDC grows without bound during development. On a project that exercises many material and ray-tracing permutations it can reach tens of gigabytes. Periodically wiping it is a legitimate way to reclaim disk space, accepting the recompile cost.

If disk space is the actual concern, the Debloat Guide covers larger and more permanent savings.

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