Let’s face it: not every Umbraco 13 website will be ready to upgrade before December 14, 2026.
The budget may already be committed. Developers may be working through another release. The website may include custom packages, integrations, or backoffice extensions that need more investigation than anyone expected.
Rushing a major CMS upgrade to meet a date on the calendar is not always the best decision. Leaving the website without security patches is not a good answer either.
Umbraco 13 Extended Long-Term Support, or XLTS, provides another option. It keeps critical security patches available for 6, 12, or 24 months after Umbraco 13 reaches End-of-Life, giving your team time to prepare the upgrade properly.
What happens to Umbraco 13 after December 14, 2026?
Your Umbraco 13 website will not suddenly stop working on December 15.
Visitors will still be able to open pages. Editors will still be able to log in. Existing integrations and forms should continue operating as they did before.
What changes is the support status.
After December 14, 2026, standard security patches and updates for Umbraco 13 will stop. If a new vulnerability is found after that date, projects without XLTS will not receive an official patch from Umbraco HQ.
That can become difficult to explain during:
Security reviews
Customer or supplier assessments
Cyber insurance renewals
Public-sector procurement
GDPR and contractual reviews
Internal technology audits
Using unsupported software does not automatically mean that an organisation has breached a regulation.
However, it can make it harder to demonstrate that known vulnerabilities are being managed and that the software supporting the service is properly maintained.
What is Umbraco 13 XLTS?
Umbraco 13 XLTS is an extension of the security period for organisations that cannot complete an upgrade before End-of-Life.
Coverage is available for 6, 12, or 24 months. It begins immediately after Umbraco 13 reaches EOL and must continue without gaps. Security updates are supplied through a private NuGet feed.
XLTS can be useful when:
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The current project has extensive custom code
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Several business systems depend on the website
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Package compatibility still needs to be confirmed
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The upgrade budget is scheduled for a later period
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The required Umbraco developers are not currently available
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The website is in maintenance mode
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A redesign or wider digital programme is already planned
In these situations, XLTS offers a controlled way to keep the current version patched while the next step is prepared.
What XLTS does, and what it does not do
XLTS provides critical security patches for Umbraco 13 after its normal support period ends.
It does not bring new CMS features to the website. It does not modernise custom code, replace old packages, improve the content model, or prepare the site for future Umbraco versions.
The feature set stays frozen, and the project still needs to be upgraded or rebuilt later. Umbraco describes XLTS as a temporary extension rather than a replacement for being on a supported release.
That distinction matters.
XLTS works well when it is bought alongside an agreed upgrade plan. It becomes much less useful when the additional months pass without any preparation.
A sensible use of the extra time
The first part of the XLTS period should be used to understand what is actually involved in taking the website from Umbraco 13 to Umbraco 17.
That assessment should cover more than the CMS version number.
Review custom code and backoffice extensions
Umbraco 17 uses the newer backoffice architecture introduced after Umbraco 13. Any custom dashboards, property editors, authentication extensions, notification handlers, or backoffice plugins need to be reviewed.
Some may only need updating. Others may need to be rewritten or replaced.
Confirm package compatibility
Every installed package should be checked against Umbraco 17 and .NET 10.
This includes packages used for forms, search, redirects, commerce, personalisation, media handling, translation, analytics, and deployment. Umbraco’s upgrade guidance also recommends checking that custom code works with the updated .NET version.
Map the integrations
The website may exchange data with a CRM, ERP, product database, identity provider, payment service, marketing platform, search service, or internal API.
Each integration needs an owner, a test case, and an agreed result before launch. An upgrade can appear successful while an integration fails quietly in the background.
Review hosting and deployment
A major upgrade is a useful point to examine environments, build pipelines, infrastructure, logs, backups, disaster recovery, access permissions, and release procedures.
The website does not have to change hosting as part of the upgrade. However, combining the two decisions may make sense when the current operational setup also needs work.
Plan content and editor testing
Technical testing alone is not enough.
Editors should test the pages and tasks they use most often: creating content, managing media, publishing in several languages, reviewing forms, updating navigation, scheduling campaigns, and restoring earlier versions.
This helps identify backoffice issues before they reach the production environment.
Can Umbraco 13 be upgraded directly to Umbraco 17?
Umbraco supports a direct LTS-to-LTS upgrade from Umbraco 13 to Umbraco 17, with the CMS applying the required migrations.
That does not mean every project should follow the same route.
There are two broad approaches:
Upgrade the existing project
This can work well when the current implementation is understood, customisation is limited, packages have supported replacements, and the existing architecture is worth carrying forward.
The benefit is continuity. The trade-off is that old decisions and accumulated maintenance work may also come across.
Build a new Umbraco 17 solution and migrate the content
A new implementation may be a better fit when the current website has older backoffice extensions, outdated packages, complicated content structures, or years of changes layered on top of one another.
Umbraco also presents these as the two main paths from version 13 to 17: upgrading the existing solution or preparing a new Umbraco 17 solution and transferring the content and schema.
The right answer depends on the website itself. An assessment should compare the cost, delivery time, testing effort, and longer-term maintenance implications of both routes.
Why Umbraco 17 is the destination
Umbraco 17 is the current Long-Term Supported version of Umbraco CMS. It runs on .NET 10 LTS and is supported until November 27, 2028.
For an organisation still using Umbraco 13, the upgrade is not only about avoiding an EOL date. It is also an opportunity to review:
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Editor experience
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Page and component design
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Package use
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Custom code
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Accessibility
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Performance
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Deployment
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Hosting
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Monitoring
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Security controls
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Ownership and documentation
Not every area needs to be changed. The value comes from deciding what should be retained, what should be updated, and what should not be carried into the next version.
Should you choose XLTS or start the upgrade now?
Choose XLTS when the Umbraco 17 work cannot be completed and tested before December 14, 2026.
Start the upgrade now when the project can be assessed, funded, built, and released within the remaining support period.
Some organisations may do both: purchase XLTS to protect the website after EOL while beginning the Umbraco 17 project immediately. This can reduce deadline pressure and allow more time for integration testing, content checks, security review, and a staged launch.
The decision should be based on the state of the current website rather than the deadline alone.
XLTS buys time. Use it well.
There is nothing unusual about needing more time for an Umbraco upgrade.
Enterprise and public-sector websites often have dependencies that cannot be changed quickly. XLTS recognises that reality and provides a supported way to continue receiving security patches while the work is prepared.
The important part is what happens next.
Treat XLTS as the opening stage of the Umbraco 17 programme. Assess the current project, choose between an upgrade and a new implementation, confirm the budget, assign the team, and agree on a delivery date.
As an Umbraco Gold Contributing Partner, Phases can review your Umbraco 13 setup and help determine whether XLTS, a direct upgrade, or a new Umbraco 17 implementation is the better route.
Speak with a senior Umbraco engineer about your current version, custom code, packages, integrations, and available timeframe.