Umbraco 17 LTS: .NET 10, a Scalable Backoffice and More

Umbraco 17 was released on November 27, 2025. It is a Long-term Support release built on .NET 10 LTS, giving organisations a modern CMS foundation with a predictable support window through November 2028.

The release completes an important chapter for Umbraco. Version 14 introduced a completely new backoffice architecture. Versions 15 and 16 developed that foundation with improved caching, multilingual content tools, API authentication, a new Rich Text Editor and a more refined editorial experience. In Umbraco 17, the modern backoffice has reached the maturity, feature parity and ecosystem support expected from an LTS version.

For teams already using Umbraco 16, the headline additions are load balancing for the entire backoffice and consistent UTC date handling. For teams moving from Umbraco 13, the change is broader: Umbraco 17 brings together two years of platform development and a new way of building backoffice extensions.

Current status: Umbraco 17 is the current LTS release recommended by Umbraco HQ for most projects. It remains supported until November 27, 2028.

Umbraco 17 is the current Long-term Support release.

.NET 10 and C# 14

Umbraco 17 runs on .NET 10, Microsoft’s current Long-term Support release. .NET 10 is supported until November 14, 2028, so the CMS and its underlying runtime have closely aligned support periods.

For developers, .NET 10 continues the focus on performance, security, diagnostics and cloud-ready applications. ASP.NET Core 10 includes improvements to OpenAPI, Minimal APIs, observability and memory management. The practical result is a stronger foundation for high-traffic websites and applications that need clear monitoring, efficient resource use and reliable deployment.

Umbraco 17 projects can also use C# 14 features, including extension members, field-backed properties, null-conditional assignment and additional Span<T> conversions. These language improvements will not transform an existing codebase by themselves, but they can make new application and integration code more concise and maintainable.

As with every runtime upgrade, the real benefit depends on the complete solution. Custom code, database access, caching, frontend delivery and hosting configuration still need to be designed and measured correctly.

A Long-term Support release

Umbraco publishes a new major version every six months, but only every fourth major version is designated LTS. The longer lifecycle makes Umbraco 17 the natural target for organisations that value stability and do not want to adopt every Standard-term Support release.

Version	Release date	Release type	Security-only phase begins	End-of-Life
Umbraco 17	November 27, 2025	LTS	November 27, 2027	November 27, 2028

During active support, the release receives bug fixes and security updates. The final year is the security-only phase, after which the version reaches End-of-Life. Planning the next upgrade before that date should be part of the product roadmap and budget—not an emergency task once support has already ended.

Load balancing the entire Umbraco backoffice

Load balancing is one of the most important architectural improvements in Umbraco 17.

Earlier Umbraco versions could distribute the public-facing website across multiple application servers, but the backoffice still had to run on one designated server. That server became a potential bottleneck and single point of failure, particularly for large editorial teams, media-heavy platforms and multi-region environments.

Umbraco 17 allows the complete application—including the backoffice—to run across multiple instances. An incoming request can be handled by any suitable server, enabling the platform to scale horizontally as traffic and editorial activity grow.

The main business benefits are:

improved resilience because editorial work no longer depends on one backoffice server;
more capacity for teams with many concurrent editors;
simpler infrastructure, with one application model for the website and backoffice;
more flexibility when deploying across regions or scaling for peak demand;
reduced disruption when an individual application instance restarts or becomes unavailable.

The implementation required more than distributing HTTP requests. Umbraco introduced cache-version coordination for repository and isolated caches, moved distributed background-job tracking into the database and ensured that long-running operation state is shared between instances instead of being kept in local files.

Load balancing still needs an infrastructure design. Teams must configure a shared database and storage where required, route traffic correctly, and provide a scale-out mechanism for SignalR. Deployment, cache behaviour and failure scenarios should be tested under realistic load. Umbraco 17 provides the CMS foundation; it does not replace an operational architecture.

Consistent UTC dates across regions

Date handling can become surprisingly difficult when application servers, editors and website visitors operate in different time zones. A publishing time that is interpreted differently by two servers can result in content appearing too early, too late or inconsistently.

In Umbraco 17, system dates are stored and exposed consistently in Coordinated Universal Time (UTC). This includes creation and update timestamps, publishing schedules, audit information and log-related dates. Each server therefore works from the same unambiguous point in time, regardless of its local region or time-zone setting.

Consistent UTC storage gives every server and editor the same reference point.

The upgrade includes a built-in migration for existing system dates, and the migration behaviour can be configured. Importantly, editor-managed content properties are not automatically converted. A content field such as an event start time may have its own business meaning, so changing it without project-specific rules could corrupt the intended value.

Before an upgrade, teams should therefore review custom date properties, scheduled jobs, integrations and frontend formatting. Store a precise moment in UTC where appropriate, preserve a local date where the business meaning requires it, and convert values for display at the edge of the application.

New date and time property editors

Umbraco 17 adds clearer property editors for different date and time scenarios:

date only;
time only;
a date and time without an associated time zone;
a date and time with an associated time zone.

This distinction helps document intent in the content model. A birthday is a date, a recurring opening time may be a time, while an international webinar normally represents a precise moment associated with a time zone.

The time-zone-aware Date Time Picker in Umbraco 17. Screenshot captured from the official Umbraco 17 Release Candidate demonstration.

A mature and more accessible backoffice

The backoffice introduced in Umbraco 14 is based on TypeScript, Web Components, Lit and the Umbraco UI Library. It communicates through the Management API and replaces the previous AngularJS extension model.

By version 17, Umbraco HQ describes this architecture as mature and polished, with feature parity with Umbraco 13 and a package ecosystem that has had time to catch up. That is an important distinction for LTS adopters: version 17 is not the first release of the new interface, but the result of several release cycles of testing and refinement.

The release also includes improvements resulting from an accessibility audit. Many identified issues were resolved in version 17, with remaining work scheduled for subsequent minor releases. Better focus handling, labels, keyboard interaction and visual feedback benefit editors who use assistive technology, while also making the backoffice clearer for everyone.

Two smaller improvements show the attention given to everyday editorial work.

More useful collection views

Collection-based content can avoid cluttering the navigation tree with hundreds or thousands of child items. However, hiding those items could also remove useful context while an editor was working on one of them. In Umbraco 17, the tree can reveal the relevant collection items when one is active, making it easier to understand where the current document sits and move between related items.

Collection items appear in context while an editor works on an active document. Screenshot captured from the official Umbraco 17 Release Candidate demonstration.

Entity signs

Entity signs communicate an item’s state directly in the content tree. Core signs can show that a document is protected or has scheduled publishing, and a tooltip provides more information. The system supports multiple signs and is extensible, so packages and custom solutions can add states relevant to their own workflows.

Entity signs make important document states visible without opening each item. Screenshot captured from the official Umbraco 17 Release Candidate demonstration.

What changed between Umbraco 13 and 17?

Teams following only the LTS releases will encounter more than the features introduced specifically in version 17. The route from Umbraco 13 also includes the main changes delivered in versions 14, 15 and 16:

Umbraco 14: a new backoffice architecture, modern Extension API and Management API replaced the AngularJS-based administration layer and legacy backoffice APIs;
Umbraco 15: HybridCache introduced lazy-loaded published-content caching, alongside block-level variants, client credentials and the new Tiptap-based Rich Text Editor;
Umbraco 16: the Tiptap editor became the established default, while property-level editing permissions, segment support and additional extension points refined the editor and developer experience;
Umbraco 17: the platform moved to .NET 10 LTS, added full backoffice load balancing and consistent UTC dates, and consolidated the modern backoffice as the long-term foundation.

This is why a move from version 13 should be treated as a solution upgrade rather than only a NuGet package update. The database migration may be automated, but the application around it still needs deliberate technical work.

Upgrading directly from Umbraco 13 to 17

Umbraco officially supports a direct LTS-to-LTS upgrade from version 13 to version 17, with core migrations applied automatically. That is good news, but it does not mean every project will upgrade without changes.

There are two realistic paths.

1. Upgrade the existing solution

Update the current project and packages, run the Umbraco migrations, adapt custom code and validate the upgraded solution. This route can work well when the application is healthy, its architecture is understood and most dependencies already support version 17.

It usually offers greater continuity and may require less initial work. The trade-off is that existing technical debt and older design decisions are more likely to be carried into the new version.

2. Build a fresh Umbraco 17 solution

Create a clean version 17 project, then move content and schema using Umbraco Deploy import/export or a project-specific migration process. Umbraco Deploy can transform legacy schema and content during import, with custom migrators for solution-specific structures.

This path requires more discovery and planning, but it creates room to replace obsolete packages, redesign fragile integrations, simplify content models and modernise hosting. It is often the better fit when a version 13 solution contains substantial custom backoffice code, legacy data or accumulated technical debt.

Whichever path is selected, the migration assessment should cover:

custom AngularJS property editors, dashboards, sections and trees that must be rebuilt using the modern Extension API;
third-party package compatibility, licensing and replacement options;
custom backoffice APIs, authentication flows and Management API integrations;
Tiptap configuration and any TinyMCE plugins or rich-text processing rules;
date assumptions in content, scheduled jobs, external systems and database queries;
cache seeding, distributed caching, SignalR and load-balancing infrastructure;
automated tests, content validation, redirects, SEO and performance baselines;
deployment procedures, rollback planning and editor acceptance testing.

There is also a .NET 10-specific project change to check. Microsoft deprecated Razor runtime compilation, and Umbraco moved the components required for Razor runtime compilation and the InMemoryAuto Models Builder mode into a separate package. Projects that rely on either feature need to reference and configure that package explicitly—or use the recommended modern development workflow.

Should you upgrade to Umbraco 17?

For a new long-lived project, Umbraco 17 is the appropriate LTS baseline. For an existing Umbraco 13 project, the timing is more urgent: version 13 reaches End-of-Life on December 14, 2026. After that date, it will no longer receive standard fixes or security patches from Umbraco HQ.

An upgrade is particularly valuable when the organisation needs:

support and security updates beyond 2026;
a modern, supported backoffice extension model;
better resilience for large websites or editorial teams;
reliable scheduling across servers and time zones;
current package versions and a maintainable .NET platform;
an opportunity to reduce technical debt before the next phase of development.

The right first step is a short technical discovery. It should identify what can be upgraded directly, what needs to be rebuilt and whether an in-place upgrade or clean implementation gives the better long-term result.

We can help you upgrade your Umbraco application

At CodeMasters Solutions, we have delivered commercial Umbraco projects and migrations from legacy versions such as Umbraco 6 and 7 to modern .NET-based releases.

We can help you with:

an audit of your existing Umbraco solution;
package, custom-code and backoffice-extension analysis;
an upgrade strategy, risk assessment and estimate;
rebuilding AngularJS extensions for the modern backoffice;
content, schema and integration migration;
automated testing, performance optimisation and load-balancing design;
deployment and post-migration support.

Moving to Umbraco 17 is an opportunity to do more than extend the support date. With the right plan, it can produce a platform that is easier to operate, safer to develop and ready to grow with the organisation.

Contact CodeMasters Solutions to discuss an Umbraco 13 audit, an Umbraco 17 implementation or your next migration.