# Unreal (5.4.4 and 5.6 Preview) Lightmass on Mac stopping at 0% **URL:** \ **Category:** Rendering\ **Tags:** apple, Lightmass, building-lighting, baked-lighting, Macos, unreal-engine, question\ **Created:** [May 27, 2025, 7:08pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543 "2025-05-27T19:08:22Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![GameAnim](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/gameanim/32/1075878_2.png) [@GameAnim](https://forums.unrealengine.com/u/GameAnim)\ **Post date:** [May 27, 2025, 7:08pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/1 "2025-05-27T19:08:23Z")
I am unable to get Unreal to build lighting on an Apple MacBook Pro M4, with it stopping at 0% before failing, and offering no errors beyond: ```auto LogStaticLightingSystem: Warning: Failed to build lighting!!! Lighting build failed. DumpUnbuiltLightIteractions Lights with unbuilt interactions: 0 Primitives with unbuilt interactions: 0 Cmd: MAP CHECK NOTIFYRESULTS MapCheck: Map check complete: 0 Error(s), 0 Warning(s), took 0.09ms to complete. ``` I have followed tutorials for building lights, but no success. This was in 5.4.4 and I see the same in the 5.6 preview. I have found a couple of other posts mentioning the same issue, but none with a resolution that works (others mention lightness requiring a firewall exception but mine is off). Is it the case that baked lighting (like GPU Lightmass) is simply untested or unavailable on Apple Silicon? I can’t find any official mention of this on Epic announcements. Has anyone else successfully built lighting on an M4 Mac? ---
**Author:** ![brs-sebascova](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/brs-sebascova/32/1052483_2.png) [@brs-sebascova](https://forums.unrealengine.com/u/brs-sebascova)\ **Post date:** [May 27, 2025, 8:50pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/2 "2025-05-27T20:50:30Z")
Hello there @GameAnim! Checking around the community, baked lighting is supported on Apple Silicon, but it does come with a few quirks and conflicts. The overall recommendation in those threads was to switch to Lumen instead. Since your build is not returning a concrete error, it would be a good approach to test. To setup lumen in your scene, go to Project Settings \> Rendering Global Illumination, then set “Dynamic Global Illumination” and “Reflection” methods to Lumen. ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/7/1/27180de6cbe06104e9b07349f084c65a019d7c42.png) You can find further information on the feature following the guides below: > **[Introduction to Lumen | Community tutorial](https://dev.epicgames.com/community/learning/tutorials/az8a/unreal-engine-introduction-to-lumen)** > > Understanding the fundamentals of Lumen in Unreal Engine. > **[Lumen Global Illumination and Reflections in Unreal Engine | Unreal Engine...](https://dev.epicgames.com/documentation/en-us/unreal-engine/lumen-global-illumination-and-reflections-in-unreal-engine)** > > Take a look at a high-level overview of Lumen's dynamic global illumination and reflections features of Unreal Engine. > **[Beginner's guide to lighting and rendering using Lumen and ACES in Unreal...](https://dev.epicgames.com/community/learning/tutorials/6P9e/beginner-s-guide-to-lighting-and-rendering-using-lumen-and-aces-in-unreal-engine-5)** > > In this video, we look at lighting a basic scene in Unreal Engine 5.3 using > lumen and the ACES color workflow. I will go over the basic project setup > a... ---
**Author:** ![GameAnim](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/gameanim/32/1075878_2.png) [@GameAnim](https://forums.unrealengine.com/u/GameAnim)\ **Post date:** [May 28, 2025, 8:44am UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/3 "2025-05-28T08:44:46Z")
Thanks for responding [@brs-sebascova](https://dev.epicgames.com/community/api/user_profiles/tab-redirect/about?discourse_username=brs-sebascova), however Lumen is runtime and not baked lighting so the solution to baked lighting not working cannot be to not use it. Has anyone here successfully used baked lighting on Apple Silicon hardware? ---
**Author:** ![TommyBoy](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@TommyBoy](https://forums.unrealengine.com/u/TommyBoy)\ **Post date:** [June 6, 2025, 4:13pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/4 "2025-06-06T16:13:12Z")
I’m having the same issue with the release version of 5.6. I cannot bake lighting. I’m in a VR template right now on a brand new Mac Studio. ---
**Author:** ![siqso\_99](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@siqso\_99](https://forums.unrealengine.com/u/siqso_99)\ **Post date:** [June 11, 2025, 8:44pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/5 "2025-06-11T20:44:09Z")
this isnt exlucsive to mac, i cannot bake lighting on windows either. Wait for a patch ---
**Author:** ![Daniel\_Garibotti](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Daniel\_Garibotti](https://forums.unrealengine.com/u/Daniel_Garibotti)\ **Post date:** [June 26, 2025, 1:59am UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/6 "2025-06-26T01:59:39Z")
Hi, is there a way to track the issue? Is it officially acknowledged and is planned for some release ? ---
**Author:** ![TommyBoy](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@TommyBoy](https://forums.unrealengine.com/u/TommyBoy)\ **Post date:** [August 1, 2025, 7:01pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/7 "2025-08-01T19:01:44Z")
That is a swarm issue… just download the file here and follow the instructions on where to put it in the engine… [UE 5.6 has no swarm manager - #5 by Arkiras](https://forums.unrealengine.com/t/ue-5-6-has-no-swarm-manager/2539483/5) The guy provides a file called dotnet.zip ---
**Author:** ![SirBatista](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@SirBatista](https://forums.unrealengine.com/u/SirBatista)\ **Post date:** [November 7, 2025, 11:12pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/8 "2025-11-07T23:12:26Z")
Just following up that this issue is still present on an M4 Mac. Much like @GameAnim I have my firewall off and attempted to bake static lighting on 5.5.4, 5.6.1, and 5.7.0 Preview. In every version Lightmass seems to not properly run and fail at 0%. I’ve seen other posts around this and none of them seem to have a solution. Shame to see the traditional pipelines tossed to the side over features that limit a product’s audience to people with the latest nvidia gpus… ---
**Author:** ![shanayyy42](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@shanayyy42](https://forums.unrealengine.com/u/shanayyy42)\ **Post date:** [December 2, 2025, 2:49pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/9 "2025-12-02T14:49:52Z")
5.7 release still can’t build lighting. ---
**Author:** ![jubileestudios](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@jubileestudios](https://forums.unrealengine.com/u/jubileestudios)\ **Post date:** [February 17, 2026, 1:12am UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/10 "2026-02-17T01:12:13Z")
Same! Can’t build lighting (just fails with no helpful error at all: “Lighting build failed.”), and I can’t use Lumen because I’m trying to create an app for iOS. Anyone? FWIW, I was able to building lighting in 5.5.4 but can’t in 5.7.1 or 5.7.3. I’m dead in the water and desperate here. Mac Studio / M3 Ultra ---
**Author:** ![jubileestudios](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@jubileestudios](https://forums.unrealengine.com/u/jubileestudios)\ **Post date:** [February 20, 2026, 2:38pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/11 "2026-02-20T14:38:11Z")
But isn’t swarm only used on PC? This is a Mac bug. ---
**Author:** ![jubileestudios](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@jubileestudios](https://forums.unrealengine.com/u/jubileestudios)\ **Post date:** [February 20, 2026, 2:38pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/12 "2026-02-20T14:38:45Z")
Find any solution yet? I’m in the same boat and dead in the water. ---
**Author:** ![Bloup](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Bloup](https://forums.unrealengine.com/u/Bloup)\ **Post date:** [April 11, 2026, 12:59am UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/13 "2026-04-11T00:59:56Z")
Same issue on 5.7.4 on a m1 mac ---
**Author:** ![Bloup](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Bloup](https://forums.unrealengine.com/u/Bloup)\ **Post date:** [April 21, 2026, 10:32pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/14 "2026-04-21T22:32:07Z")
Same issue on 5.7.4 on M1 Max as well, 5.5.4 works. It was probably broken due to one of those CLs that were pushed for 5.6-preview-1 : - 391cd45 UnrealLightmass: enable building against Embree 3 and 4 - 5d2e7ef UnrealLightmass: use the engine’s version of Embree I tried building a local version with those CLs reverted but could not manage to build with Xcode 26.. @mattyjams any idea ? 🙂 ---
**Author:** ![GameAnim](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/gameanim/32/1075878_2.png) [@GameAnim](https://forums.unrealengine.com/u/GameAnim)\ **Post date:** [April 22, 2026, 12:39pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/15 "2026-04-22T12:39:09Z")
I finally found a solution - I bought a PC. After a year of updates and no movement on this it’s clear this is not going to be fixed as Epic pushes everyone towards Lumen. ---
**Author:** ![Bloup](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Bloup](https://forums.unrealengine.com/u/Bloup)\ **Post date:** [April 22, 2026, 6:41pm UTC](https://forums.unrealengine.com/t/unreal-5-4-4-and-5-6-preview-lightmass-on-mac-stopping-at-0/2530543/16 "2026-04-22T18:41:55Z")
Well, resolving the issue sure won’t get it any attention 😕