What "end of life" actually means
Umbraco 13 was released on 14 December 2023 as a Long-Term Support (LTS) version: 24 months of full support, followed by 12 months where Umbraco HQ only ships security fixes. That security phase ends on 14 December 2026. After that date, Umbraco 13 gets nothing: no security patches, no bug fixes, no official support from Umbraco HQ. The software keeps running exactly as it did the day before, it just stops getting fixed.
Why this affects so many sites
Umbraco 13 wasn't a minor release, it was the flagship LTS version for two full years. Every new build and every migration project between December 2023 and the release of Umbraco 17 in late 2025 was, by default, pointed at 13. If your site was built, relaunched, or migrated any time in that window, there's a good chance it's still running on it right now.
How to check what version you're running
If you're not sure, it takes about thirty seconds to find out. Log into the Umbraco backoffice and check the bottom of the content section, or the Help/About area, both of which show the running version. If you're a developer with access to the codebase, the version is set by the Umbraco.Cms package reference in the project's .csproj file.
What actually happens if you do nothing
Nothing dramatic, at first. The site doesn't switch off on 15 December. What changes is the risk profile: any security vulnerability discovered in Umbraco 13 after that date simply won't get patched, which matters more the longer the site stays on it. For anything handling customer data, payments, or personal information, that's a real compliance and cyber-insurance question, not a hypothetical one, since most insurers and auditors expect software to be within its supported lifecycle. Third-party package authors also tend to stop testing against end-of-life versions fairly quickly, so plugin and integration compatibility degrades over time too.
Your realistic options
There are a few honest paths from here, and which one makes sense depends on your timeline and budget, not on which one sounds best in a sales pitch.
- Upgrade to Umbraco 17. This is the current LTS release and the sensible default for most sites: long support runway, stable, actively maintained. For most teams reading this, this is the answer.
- Consider Umbraco 18 if you specifically want the latest features and are comfortable with a shorter, standard-term support window rather than LTS. It's a reasonable choice if you're already planning to stay on a fast upgrade cadence.
- Extended LTS (XLTS) is a paid option direct from Umbraco HQ for teams that genuinely can't hit the December deadline and need more runway before migrating. It buys time, it doesn't remove the need to eventually upgrade.
- Do nothing. Not recommended, but worth naming honestly as an option rather than pretending it isn't one. See the risk section above.
The part most EOL warnings skip
Upgrading from 13 to 17 isn't a simple package version bump, and it's worth knowing that before you scope a budget. Umbraco 14 introduced a full backoffice rewrite (new management API, new admin UI, commonly referred to as Bellissima), which sits between 13 and 17 in the upgrade path. If your site has custom backoffice extensions, dashboards, or property editors, those generally need re-implementing against the new API rather than just recompiling. Content, media, members and URL structure carry across fine; custom backoffice code is where the real work is.
A realistic timeline from here
From today, that's roughly fifteen weeks to the deadline. For a fairly standard content site with no heavy backoffice customisation, a migration to Umbraco 17 typically runs somewhere in the region of one to three weeks of actual development time, plus testing and a deployment window either side. Sites with custom backoffice extensions, complex integrations, or high content volumes take longer. Either way, starting the discovery conversation in August or September leaves room for a properly tested launch well before the deadline, rather than a rushed one in the first week of December.
If you want help with this
This is the single most common reason teams get in touch with me. I plan and run Umbraco 13-to-17 migrations for agencies and in-house teams, working under a flat $700/day rate rather than an open-ended estimate. For the general step-by-step process behind any Umbraco upgrade, not just this specific deadline, see how to upgrade Umbraco. If you're a US-based team, there's a full breakdown of how the remote, UK-based working arrangement fits around US hours on the USA coverage page. Otherwise, the services page covers migrations in more detail, and you can see how pricing and scoping actually work on the pricing page.