Hello, new user here with legacy v4.6 Umbraco web app that needs upgrading. First step I have is providing an estimate on the effort. Any words from the wise would be greatly appreciated. Any codemods/strategies to migrate data? Any suggestions and migrating to headless CMS system? Thanks. Hoping to save content. If required to start fresh that is an option. Working with non-profit client so there will be challenges.

v4.6 is super old. I'd say it's an uncommonly large leap, Umbraco-migration-wise. Look at all the C#, including in Razor files. All this needs to be migrated from .NET Framework to .NET 8. Few existing third-party NuGet packages can be reused. The Umbraco APIs have also changed a bit since v4. If there is a lot of C#, I think this will be the most time-consuming part. Any backoffice extensions will need remaking from scratch. Count the document types. Are you using stuff that is obsolete or unrecommended? Think about the actual upgrade process. Attach the live database to a development environment, upgrade Umbraco each step of the way? And/or use uSync to migrate settings and content? Take into account the amount of content. 10000 documents will require more work than 100 documents. The hosting environment will need to change as well. If this is a simple site with barely any C#, then maybe a person-week from start to go-live? We've gone from v8 to v9/10/11/12 for moderate-sized sites with moderate amounts of C# and moderate Examine/backoffice extensions in 3-5 person-weeks. We've also come to the conclusion "not worth it" for larger-than-moderate solutions, not even making estimations. And super-simple sites can be rebuilt from scratch in a few days.

Thank you so much.

Let us know how it goes 🙂

Unless you have a huge amount of content to be migrated then it is not worth the headache. Start again and create the content using more up-to-date tools and best practices. Trust me, I am currently going through the pain of a migrating a v7 site that originated in v4 and if I had to do it again it would probably have been quicker to pay someone to recreate the content in a fresh new install.