Umbraco 13 upgrade checklist: get to Umbraco 17 before December 14, 2026

Umbraco 13 is a long-term support (LTS) release. It entered its security-only phase on December 14, 2025 and reaches end of life on December 14, 2026 (source: Umbraco LTS and EOL). Umbraco 13 runs on .NET 8, which Microsoft stops supporting on November 10, 2026.

The current LTS release is Umbraco 17 on .NET 10, with end of life set for November 27, 2028. Umbraco 18 can only upgrade from version 16.4 or later, so Umbraco 17 is the natural next stop for a version 13 site.

Use this checklist to plan the jump from 13 to 17. Most of the work comes from the new backoffice introduced in Umbraco 14, so start with your customizations.

How to score it

• Give each item 2 points if it is done, 1 point if it is in progress and 0 if nobody has started it.
• Add up your points and divide the total by the maximum (2 points times the number of items).
• A score above 75% means you can schedule the work. Between 40% and 75%, close the gaps this quarter. Under 40%, start with an assessment before you commit to a date.

Plan the path

• Confirm your exact Umbraco 13 version and apply the latest 13.x patch first.
• Target Umbraco 17 LTS, not 18: Umbraco 18 only upgrades from 16.4 or later.
• Check that your hosting supports .NET 10, on Umbraco Cloud or your own servers.
• Set a launch date before December 14, 2026, with room for testing.

Backoffice and code

• List every backoffice customization built with AngularJS. Umbraco 14 removed AngularJS, so each one needs a rebuild.
• Find properties built on Nested Content or Grid Layout and plan their move to Block List or Block Grid.
• Replace macros and partial view macros with partial views or blocks in the rich text editor.
• Replace the legacy Media Picker with the default Media Picker.
• Review custom controllers under /umbraco/api, which the Management API replaced.
• Check that every package and add-on (Forms, Deploy, Workflow, community packages) has an Umbraco 17 version.

Content and data

• Back up the database and media before every test upgrade.
• Plan for the block editor data migration added in Umbraco 15. It runs during the upgrade and can take time on large sites.
• Test the upgrade on a full copy of production content, not a sample.
• Check English and French variants after the migration, field by field, on a sample of pages.

Testing and launch

• Write a test list for forms, search, member login and integrations.
• Train editors on the new backoffice before launch day.
• Run a performance and accessibility check on key templates after the upgrade.
• Freeze content during the final migration and keep a rollback plan.

Get a second opinion

Scored under 75%, or not sure how much of your backoffice needs a rebuild? Our Umbraco audit helps you size the gap and plan the upgrade.

Sources

1. Umbraco long-term support and end-of-life
   umbraco.com
2. Umbraco: find your upgrade path (version 17)
   docs.umbraco.com
3. Umbraco: breaking changes overview
   docs.umbraco.com
4. .NET and .NET Core official support policy
   dotnet.microsoft.com