Failed to Launch Editor

Whenever I try opening a 4.5 editor or project via the launcher, I get a small pop-up that only says “Error” in the header, followed by the insightful “Failed to Launch Editor” message below. No further data - no crash report.

So far tonight I’ve tried half a dozen solutions to deleting various parts of the launcher/engine and regenerating them based on Q&A’s I googled, and have deleted the entire 4.5 engine and redownloaded it as well - and restarted my computer half a dozen times.

Super frustrating, especcially because I can’t tell what’s really wrong. I copied all my projects to the 4.5 engine once it came out as well, so now I can’t work on anything either.

I believe it may have had something to do with a corrupted asset migration between two projects - the last time I used the editor I had started a migration and expected it to take a minute - but it seemingly finished in <5 seconds - so I shrugged and exited out of the editor to restart in a different project - then suddenly it wouldn’t boot up.

Please help, thanks!

Update, I got it working last night but only by running the exe directly out of the 4.5 engine folder - the same problem still persists for any 4.5 project or 4.5 engine in the launcher. Is it possibly related to windows 8.1 permissions somehow?

Could the launcher not have permission to launch the 4.5 engine? It still works with 4.4 projects though, so that seems really odd.

why not revert to an older engine version

For the moment I’m accessing my 4.5 levels via the folder exe - but when I move onto my next level I’ll likely roll back to 4.4 ya - it’s just an odd bug though that I’d like to fix, even if I’ve found a way to get around it.

Plus I was interested to see what 4.5 was capable of :slight_smile:

Hi Yvaelle,

Have you tried updating to the 4.5.1 hotfix? Some Launcher issues were fixed with this release.

If that doesn’t work, please try the troubleshooting steps linked below. Afterwards, the next step would be to try reinstalling the Launcher.

If the issue still persist, please follow the instructions at the bottom of the link and post your ‘Verbose Logs’. They will help us track down the issue.



Hi TJ! Thanks for the help - I’m using 4.5.1 but the problem persists. Here is the verbose log, I read what I could but nothing leapt out as wrong to me - your opinion is appreciated :slight_smile:

link text

Hi Yvaelle. Could you please let us know what the error message is that you get inside of the Launcher when simply trying to Launch the editor normally? (not via a project). I.e. Using the main yellow launch button, select the 4.5 and hit it. That one may be more helpful :). A screenshot would be good, it should show as some text in a white bar across the Launcher’s window

Pressing the large yellow button set to 4.5.1 results in the button briefly greying out, with “Launch” changed to “Launching…”. Nothing occurs for 5-10 seconds, then the button returns to yellow with the word “Launch” once more.

During this procedure no new processes appear in task manager. Repeated after a system restart, same results. If the white bar is the top of the launcher window frame, then no text appears at any time in this bar - otherwise no new white bar appears. If you mean the “Unreal Editor” splash with the white loading bar at the bottom while it is loading the project browser, this does not appear while accessing 4.5.1 via the launcher (any method), but does appear when launching 4.5.1 directly from the executable.

Does the Launcher immediately minimise after pressing the Launch button?

No it remains open while the Launch button is greyed out. I don’t mind though, I’ve gotten used to accessing it via the a shortcut :slight_smile:

Hey Yvaelle,

Just wanted to give you an update, we’re following up with the engine team a bit to figure out why the call we’re making to launch the editor is failing. As soon as we get more info we’ll write back here. Thanks for your patience!


Hey again, the new update Carlos mentioned is now released. Your Launcher should self-patch and then when logged in you should see in the bottom left that the version begins with 1.9.0-2350904, and there is a new Learn tab.

Could you try Launching the editor from this version, and then give us new logs?


Hey TJ and Swifty, sorry for the delay - I ended up reformatting and reinstalling - which cured my problem, if not the mystery behind it!

Thanks for your help!

I’ve had this problem every other engine version since 4.9. I’m now experiencing it in 4.15 after having it in 4.13 and 4.12, but not in 4.14. Not keen on formatting my drive or reinstalling and I’m happy to provide whatever info I can to resolve it.

What do you guys need?

Hi Antidamage,

We have modified the process for how we handle Launcher issues.

Please visit:

Here you will find information and solutions for common issues, as well as a contact form if you still need additional assistance.



Hey guys,
It just happened to me in 4.18.3 - but because i have “Run as admin” checked on the UE4Editor.exe (for obscure reasons) and i tried to “double click” on .uproject file from Total commander that was not running as admin - i.e. it tried to run applicaiton as admin without having access… So when i rerun total commander as admin then it worked fine without deleting any cached files or whatever

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This happened to me when using the source version of Unreal (4.21), what I did was I ended up rebuilding the engine in Visual Studio by right clicking my game in the IDE and selecting “Rebuild”.


Could you please explain in more detail? What does total commander mean?