V13 loses its security support on 14 December 2026, so it does have to move. But an upgrade done in a hurry - lost content, a payment integration still pointing at the old endpoint, editors locked out of a back office they no longer recognise - costs far more to unpick than the deadline ever saved.
What actually goes wrong in a bad upgrade
Most upgrade horror stories have nothing to do with the version jump itself. They're about the things around it. A property editor that silently stops saving. A CRM feed that still writes to the old field names. A media library that migrates halfway and leaves broken links across the site. A back office your team opens on Monday and simply cannot use.
The upgrade “worked”, in the narrow sense that the site now reports v17. But the business running on it is firefighting, and every fix after go-live is more expensive and more visible than it would have been before.
Getting onto a supported version is the easy half. Getting there without breaking the things your business actually relies on is the half worth paying for.
Boring is the goal
A good upgrade is one nobody outside the project notices, because the live site never wobbled and the team's Monday looked like every other Monday.
That means building and testing v17 against a copy of the live environment, working through the breaking changes and package updates there, and only cutting over once everything has been verified. The current site stays up throughout. Nothing experimental touches production.
The four things that decide the price
The honest answer to “how much is an upgrade” is “it depends” - and anyone who quotes a flat number before looking is guessing. What it depends on is short and specific:
- Custom back-office work. Umbraco rebuilt the back office in v14 with a new architecture and extension model. Standard content and templates migrate cleanly, but bespoke property editors, dashboards and content apps have to be rebuilt for the new model. This is the single biggest cost driver.
- Third-party integrations. A CRM, payment gateway or data feed may need reworking or remapping against the new APIs, especially across the .NET 8 to .NET 10 jump.
- Hosting access. A no-downtime, parallel cutover assumes control of the target environment. Locked-down or third-party-managed hosting needs planning around, not discovering mid-project.
- Content and media volume. Most sites are fine; the outliers are worth knowing about up front.
Two routes to v17
Umbraco itself describes two sensible ways to move from v13. Most standard sites upgrade in place: the existing solution is upgraded and the migrations run against it. Older or heavily customised sites are often better served by a fresh v17 build, moving content and structure across in a controlled way - a clean rebuild can be less work in the long run than dragging years of accumulated complexity forward.
The right choice is a judgement call, and it should be made before anyone quotes you a number.
If you genuinely can't move before December
Umbraco sells Extended Long-Term Support for v13, which buys 6, 12 or 24 more months of security patches past the deadline. It's a paid bridge rather than a fix - the upgrade still has to happen - but it takes the pressure off. A planned upgrade with XLTS in place beats a rushed one every time.
What a proper upgrade costs
For a standard site, we do the whole thing - v13 to v17, .NET 8 to .NET 10, no downtime, 30 days of cover - for a fixed £8,999 + VAT, agreed before we start. The scope, the exceptions and an honest FAQ are all on the fixed-price Umbraco 13 to 17 upgrade page.