I have a CMS12 solution where I can upload 2 MB files in assets pane, but 5MB files and larger fails. For a plain Alloy site, I have the same problem.
I have found this:
Step 1 is ok, but it does not work alone. For step 2, the first options does not compile and the second options throws an exception.Step 1:Step 2:
You can configure the max upload size in ConfigureServices in Startup:
x.FileSizeLimit = 52428800; // 50MB
You can also update appsettings.json:
Here's the link in the documentation: https://world.optimizely.com/documentation/developer-guides/CMS/configuration/configuring-episerver-ui