What happens when Umbraco 13 reaches end of life
Umbraco 13 is an LTS release from December 2023. Its standard support phase ended in December 2025, and since then it has received security patches only. On December 14, 2026, those stop too.
After that date there are no more security patches unless you buy an extended support contract (XLTS), no bug fixes, and package authors steadily drop support as they move to newer versions.
The earlier deadline matters more: Microsoft ends .NET 8 support on November 10, 2026. From that day, the runtime under your CMS stops receiving security fixes — regardless of what Umbraco does.
The cost of waiting
Security. Vulnerabilities found after end of life stay unpatched. Fixes published for newer versions work as a map for attackers targeting older ones.
Compliance. GDPR expects appropriate technical measures. A public website on an unsupported CMS and an unsupported runtime is hard to defend after an incident — and NIS2 raises that bar further for many EU organizations.
Ecosystem drift. Packages, integrations and hosting environments move on. Every month on Umbraco 13 adds distance to cover later.
Cost. An upgrade planned now is a normal project. An upgrade forced by a security incident is an emergency, at emergency prices.
Your options before December 2026
Upgrade to Umbraco 17 LTS
The default recommendation. Umbraco 17 runs on .NET 10 with support into late 2028, and the upgrade path from 13 is well established. The effort is driven almost entirely by your custom code, backoffice extensions and packages — which is why every upgrade starts with a compatibility review.
Buy time with extended support (XLTS)
Umbraco sells extended long-term support for organizations that cannot upgrade in time. It is a legitimate stopgap for complex estates — but it postpones the question rather than answering it, and your site still runs on a runtime Microsoft no longer supports.
Rebuild on a current foundation
If your Umbraco 13 solution carries years of technical debt, a rebuild can cost close to a heavy upgrade — and deliver far more. New builds start from the KindbergCo Umbraco Platform: a production-ready Umbraco 17 foundation with SEO structure, accessibility groundwork built against WCAG 2.2 AA principles, and performance defaults in place from day one.
Do nothing
Defensible only if the site is being decommissioned before the deadline. For anything else, it is a decision to run a public website with known, unpatched vulnerabilities.
Not sure which option fits? A short review of your solution answers it with evidence instead of guesswork.
Frequently Asked Questions
Yes — nothing switches off. But it runs without security patches unless you buy XLTS, on a runtime Microsoft stopped supporting in November 2026. If you stay past the deadline, make it a time-boxed decision with an upgrade date attached, not a default.
Bigger than a routine version bump: a new backoffice, a new Management API and a move to .NET 10. Content and document types usually migrate cleanly. The real effort sits in custom backoffice extensions, packages and integrations — a compatibility review shows exactly where.
A standard site with well-maintained code: typically a few weeks including testing. Heavily customized solutions take longer. After a review you get a written scope with approach, risks and timeline — and your editors keep working in the meantime.
No — takeovers are routine for me. I review the code and infrastructure, stabilize anything urgent, document as I go, and then run the upgrade. You do not need the original developer to move forward.
To be live on Umbraco 17 before December 14, 2026, planning should start no later than early autumn — upgrades compete with content freezes, launch windows and holiday code freezes at year end. Starting now buys you options; starting in November buys you stress.
Core knowledge
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Specializing in Microsoft technologies - C#.Net, MS SQL, etc
Strong technical knowledge
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Data integrations, data mining, and profiling
Brainstorming of new functionality as well as the implementation of such
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