Everything Umbraco has shipped this year needs Umbraco 17+.
That includes:
Umbraco AI.
The Copilot sidebar.
Umbraco Automate.
AI Search.
Every one of them requires Umbraco 17 or later, and every one of them targets .NET 10. If you are running Umbraco 13, this runs on .NET 8 and it cannot install any of it, and no future update is going to change that!
Most of what you have read about Umbraco 13 is about the deadline, and the deadline is real. We have covered it properly elsewhere: what end of life actually means, and what the upgrade costs. This post is not another one of those.
This one is about what a v13 site is already missing, and why the gap only gets wider from here.
What Umbraco 17 sites got this year
In plain terms, for the people who actually use the back office.
Umbraco AI. A free, MIT-licensed AI layer from Umbraco HQ, built into the back office. You bring your own API key from Anthropic, OpenAI, Google, Microsoft or several others, and pay the provider directly. Once it is configured, editors get one-click actions on the fields they already use: write a meta description from this page, tighten this paragraph, give me three heading options, turn this into a LinkedIn post, in your brand voice.
Copilot. A sidebar in Content and Media where editors can ask questions and get help in context, backed by agents you control. What those agents can read and write is scoped, logged and governed.
Umbraco Automate. Launched on 9 July 2026, also free. A visual workflow canvas in the back office: when this is published, do that. Notify Slack, call your CRM, run an AI agent, then stop and wait for a human to approve before anything goes live. Retries, run history and error handling included.
AI Search. Semantic search for your own site's content and media, so visitors searching for "cheap flights in March" find the page titled "Spring travel deals". It is newer than the rest and we would pilot it before selling it, but it is there.
One honest caveat, because we have written about it at length: Umbraco AI ships empty. No prompts, no agents. Someone has to configure it properly before your editors see anything useful. That is a day or two of work on a v17 site.
On a v13 site it is not a day or two, It's not available at any price.
Why "never" is the right word
This is not a case of HQ getting round to a v13 version later. The packages are built for .NET 10 and require Umbraco 17.5 or later, which we checked in the package metadata rather than trusting the docs. Umbraco 13 is a .NET 8 application. There is no compatible build and there will not be one.
It is also worth knowing where v13 has been for the last nine months. Umbraco 13's security phase started on 14 December 2025. Since then it has received security fixes and dependency updates, with only the occasional backported fix, and no new features. On 14 December 2026 the security fixes stop too.
And .NET 8 itself, the runtime underneath every v13 site, reaches end of support from Microsoft on 10 November 2026. That is five weeks before Umbraco 13 does.
So a v13 site is not standing still. It has been close to frozen for most of this year, and the platform underneath it is running out of support first.
"Can't we just bolt AI on ourselves?"
You can wire an OpenAI or Anthropic call into a v13 site. Plenty of agencies have done exactly that over the last two years.
But that gets you some of the features and none of the product around them. No HQ-maintained guardrails, no audit log of who generated what, no version history and rollback on prompts, no test framework to check the output still behaves after the model changes underneath you, no Copilot, no Automate. Just custom code you now maintain yourself, on a CMS that is about to stop receiving security fixes.
It is a reasonable thing to have built in 2024, however it is a hard thing to justify starting now.
"We'll just pay to delay"
This is the most sensible objection we hear, so here is a straight answer.
Umbraco HQ sells Extended Long-Term Support (XLTS) for version 13. It gives you 6, 12 or 24 months of critical security patches past 14 December 2026, delivered through a private NuGet feed. It has to be ordered before the end-of-life date, the cover has to be continuous with no gaps, and pricing is by conversation with HQ rather than published (btw it's not cheap!).
For some organisations it is the right call. If this year's budget is spent, or a procurement freeze makes December impossible, XLTS keeps the site patched while you plan properly. We would rather you did that than ran unpatched.
But be clear about what it buys:
Time, not the upgrade. The v13 to v17 work is exactly the same size in 2027 as it is now. XLTS moves the invoice, it does not remove it.
Security patches, nothing else. Umbraco describes XLTS as a frozen feature set. No new features, and no general bug fixes. You are paying for the site to stay as it is.
None of this year's features. XLTS does not bring Umbraco AI, Copilot, Automate or AI Search any closer. They still need 17.
Two bills instead of one. You pay for the extension, then you pay for the upgrade. Paying to delay once can be sensible. Paying to delay twice rarely is.
XLTS is a way to buy certainty about when you do the work. A fixed-price upgrade is a way to buy certainty about what the work costs. Most of the time, the second is the one worth having.
What the upgrade actually looks like
We have covered the detail in the end-of-life explainers, so briefly.
There is now a direct path from 13 to 17. Your content and media come across. The work sits in predictable places: templates and views, packages that need a v17 version or a replacement, and anything custom built for the old back office, which was rebuilt from v14 onwards.
Once you are on 17, the AI work becomes a separate, small piece of consultancy work rather than an impossibility. You can do it in the same project or leave it until your team is ready.
If you are on 13
If your site runs on Umbraco 13, here is the useful version.
You have until 14 December 2026 for security support, and until the same date to order XLTS if you need it. The upgrade itself is weeks, not months, for most sites, but build slots before Christmas are finite and content freezes make late projects worse.
We do the v13 to v17 upgrade at a fixed price, agreed before we start. A standard site is £8,999 + VAT. If your site needs more than a standard upgrade, we will tell you that before you commit, not after.
If you want to know what your site actually needs, see how we run an upgrade. We will look at it and give you a straight answer on scope, timing and price, including if the honest answer is that XLTS suits you better this year.
Contracts and invoices for the upgrade come from Simplepage Limited. Simon Antony is a brand of Simplepage Limited based upon the Isle of Man.
What else changes when you move from 13 to 17
The AI features are the headline, but they are not the only reason. For the people who have to sign off the budget, this is the technical case.
Support runway. Umbraco 17 is a long-term support release. Its security phase runs to 27 November 2027 and it reaches end of life on 27 November 2028. .NET 10, which it runs on is supported by Microsoft to 14 November 2028.
The editor experience. The back office was rebuilt from Umbraco 14 onwards on a modern web components stack. It is the change your editors will notice first.
Where the new features need you to be. Umbraco AI requires Umbraco 17.5 or later. Umbraco Automate requires 17.4 or later. If you are upgrading anyway, land on the latest 17 minor, not 17.0.