Can we directly upgrade Umbraco 13.13.1 to lastest Umbraco 17 version?

Ajeetkmr154 · May 21, 2026, 10:16am

I am trying to upgrade my Umbraco 13 application directly to Umbraco 17. I have fixed all compile/runtime error.

Now, I am not getting backoffice css/js issue. Any clue to fix this one.

justin-nevitech · May 21, 2026, 10:24am

Hi @Ajeetkmr154

Yes, you should be able to go from LTS to LTS, just make sure you are on the latest version of your starting LTS first.

In regards to your JS/CSS errors, what does the browser dev tools network tab show and does your front-end render?

Justin

Ajeetkmr154 · May 21, 2026, 10:59am

Hi @justin-nevitech ,

Yes, I am upgrading from latest LTS(U13.13.1) to LTS(U17.3.2)
No, front-end not rendered yet. These are the below network tab details

umb-css.css	404	stylesheet	umbraco:14	371 B	23 ms
uui-css.css	404	stylesheet	umbraco:15	371 B	15 ms
app.element.js	404	script	umbraco:20	379 B	19 ms

justin-nevitech · May 21, 2026, 11:22am

Hi @Ajeetkmr154

I can see a Visual Studio icon in your screenshot so I assume you are running through that. Does it work if you try via Kestrel using:

dotnet run

Justin

Ajeetkmr154 · May 21, 2026, 1:35pm

Hi @justin-nevitech ,

I tried but getting same error. I have verified that page source in the browser.

I am getting empty body. Please see below screenshot

justin-nevitech · May 21, 2026, 2:04pm

Can you post your .csproj and Program.cs files?

Ajeetkmr154 · May 21, 2026, 2:23pm

Hi @justin-nevitech , Thank you so much for quick response.

Issue has been fixed. Actually, we are using gulp command to generate css/js file and In my machine db service was also not running. After fixing those and ran application through gulp command. Upgrade completed successfully.

Thank you again for your help!