Umbraco 13 reaches end of life on 14 December 2026: upgrade to 17 or move to Sanity?

What does Umbraco 13's end of life on 14 December 2026 change?

Umbraco 13's end of life on 14 December 2026 ends security patches and updates; the site keeps running, against Umbraco's strong advice (Umbraco, Umbraco 13 End-of-Life, October 2026). From 24 October 2026, 51 days remain (Deploi arithmetic from Umbraco's dates). Umbraco 18 can't upgrade from Umbraco 13, so Umbraco 17 is the landing point (Umbraco Docs, Find Your Upgrade Path; Breaking Changes Overview, October 2026). Umbraco 13's runtime, .NET (Microsoft's development platform) 8, loses support sooner, on 10 November 2026 (Microsoft, October 2026); the deadline calendar lists both.

What does upgrading Umbraco 13 to Umbraco 17 involve?

Upgrading Umbraco 13 to Umbraco 17 is an in-place NuGet upgrade that also moves your project from .NET (Microsoft's development platform) 8 to .NET 10 (Umbraco Docs, Upgrade Your Project, October 2026). The work sits in the releases you cross on the way (Umbraco Docs, Find Your Upgrade Path, October 2026):

• Umbraco 14 removed AngularJS from the backoffice, so every AngularJS property editor, dashboard or package extension is rewritten; the new backoffice is built with TypeScript, Web Components and Lit (Umbraco blog, October 2026).
• Umbraco 14 also removed Nested Content, Grid Layout, the legacy Media Picker and macros. Umbraco recommends rebuilding them with Block Grid or Block List.
• Umbraco 15 changed the Block Editor data format, and the content migration "can take a while" on a large site, which stays unresponsive while it runs.
• Umbraco 16 removed the TinyMCE option of the Rich Text Editor, which is now built on Tiptap (Umbraco Docs, Rich Text Editor, October 2026).

A site built on Block List, Block Grid and the built-in editors carries little of this list. A site with years of custom AngularJS backoffice code carries most of it (Deploi's judgment).

Should an Umbraco 13 site upgrade in place or rebuild on Umbraco 17?

An Umbraco 13 site should upgrade in place when it's healthy and well understood, and rebuild on Umbraco 17 when it carries legacy backoffice code; that's Umbraco's own split (Umbraco blog, Going from Umbraco 13 to 17, October 2026). Umbraco names two paths:

• In place. Upgrade the existing solution and run the migrations.
• Fresh build. Build a fresh Umbraco 17 solution and move content and schema with Umbraco Deploy's import and export.

Umbraco's blog goes further: "For most cases, it makes more sense to build fresh on Umbraco 17." Read that as vendor opinion, because the same post sells Umbraco Cloud, which includes Umbraco Deploy with every plan.

The split matters for a Sanity decision because it changes what you compare. An in-place upgrade against a Sanity migration is lopsided: one keeps your content model, views and hosting, the other replaces all three. A fresh Umbraco 17 build against a Sanity build is two rebuilds of the editing layer, which is where the cost of moving comes closest to the cost of staying (Deploi's judgment).

When does replatforming from Umbraco to Sanity win?

Replatforming from Umbraco to Sanity wins when you're rebuilding the backoffice anyway and one content model has to feed several channels. Going headless isn't a reason on its own, because Umbraco 13 and 17 ship an opt-in Content Delivery API (application programming interface) that serves content as JSON (Umbraco Docs, Content Delivery API; current version, October 2026). Sanity Studio, Sanity's editing app, is an open-source React app that connects to Sanity's hosted APIs and Content Lake (Sanity Docs, Hosting and deployment, October 2026).

Three situations favor the move:

• Custom AngularJS editors, dashboards or Grid Layout pages make Umbraco 17 a rebuild too.
• The same content feeds several sites, apps or brands, which is the case for running several sites from one content platform.
• Your front end is moving to a JavaScript framework, and your team wants rich text as Portable Text, a JSON rich text format. Umbraco's Rich Text Editor returns HTML (Umbraco Docs, October 2026), and its Content Delivery API outputs HTML unless you enable RichTextOutputAsJson (Umbraco Docs, October 2026).

When should you stay on Umbraco, buy XLTS, or pick a CMS other than Sanity?

Stay on Umbraco when the upgrade audit is small or policy says you host the content database, because Sanity hosts it and you can't self-host the Content Lake (Sanity Docs, Studio development, October 2026). Buy Extended Long-Term Support (XLTS) only to bridge a funded plan: 6, 12 or 24 months from the day after end of life, security patches only, quoted on request (Umbraco, Umbraco 13 XLTS, October 2026). Umbraco Heartcore is Umbraco's hosted headless content management system (CMS) (Umbraco, Heartcore, October 2026).

What changes for Umbraco editors and .NET developers on Sanity?

Umbraco editors move from Umbraco's backoffice to Sanity Studio, and .NET (Microsoft's development platform) developers move to JavaScript or TypeScript, because you configure Sanity Studio in code (Sanity Docs, Configuration, October 2026). Three things change for the team:

• Where the content model lives. Document Types, Element Types and Block List blocks become Sanity document and object types, defined in code instead of in the backoffice.
• What renders the site. The front end reads content from Sanity's APIs (application programming interfaces) instead of Umbraco; whether a .NET back end can keep reading it is answered in Sanity with PHP, .NET or Java.
• Who can publish. Sanity's Growth plan has five fixed roles, including a Contributor who "Can write but not publish documents" (Sanity Docs, Roles, October 2026). Anything finer needs custom roles, which are Enterprise only as of October 2026 (Sanity pricing).

The Umbraco to Sanity playbook maps each Umbraco user group, Document Type and block to its Sanity equivalent, so the mapping lives there.

How do you compare the cost of staying on Umbraco with the cost of moving to Sanity?

Compare staying on Umbraco with moving to Sanity driver by driver, over the same horizon: Umbraco 17's end of life on 27 November 2028, about two years after Umbraco 13's (Deploi arithmetic from Umbraco's schedule, October 2026). Umbraco's open-source core is free (Umbraco on GitHub, October 2026), but add-ons such as Umbraco Forms are paid (Umbraco, Umbraco Forms, October 2026). Sanity's Growth plan costs $15 per seat a month, billed monthly, as of October 2026 (Sanity pricing).