.NET 10 LTS shipped on November 11, 2025 and will be supported through November 14, 2028. That three‑year runway is the main reason enterprises standardize on LTS: predictable security fixes, time to amortize migration costs, and fewer moving parts during compliance audits. If you’ve held on to .NET 8 or rode .NET 9 (STS), this is the moment to consolidate. (dotnet.microsoft.com)
Here’s the thing: .NET 10 LTS isn’t just a support story. The runtime is faster and smarter, ASP.NET Core 10 tightens security defaults, the SDK smooths container builds and native publishing, and C# 14 removes small frictions you hit every day. If you approach the upgrade like a product release—not a lift‑and‑shift—you’ll bank performance, simplify code, and reduce auth headaches.
What’s new in .NET 10 LTS that actually moves the needle
Runtime and performance: real gains with fewer gotchas
The runtime brings better JIT inlining and devirtualization, more aggressive stack allocation (including small arrays), and NativeAOT improvements that shrink and speed self‑contained apps. There’s also new AVX10.2 intrinsic support queued up for future x64 hardware; it’s present but off by default until chips land. Translation: you’ll see gains today without betting on tomorrow’s CPUs. (learn.microsoft.com)
SDK and tooling: simpler containers and native executables
Shipping console tools or CLIs? File‑based apps now publish directly to native executables with a single command, and target NativeAOT by default. The SDK’s CLI gained schema introspection and a standardized command order, plus better first‑run shell completions. For containers, you can explicitly set image formats and generate images from console apps without extra scaffolding. These are small, practical delighters that shave release time. (learn.microsoft.com)
ASP.NET Core 10: safer defaults and better signals
Web apps and APIs see meaningful changes. ASP.NET Core 10 enables passkey (WebAuthn/FIDO2) support in Identity, adds automatic memory pool eviction to curb bloat in long‑running processes, expands built‑in metrics for authentication and Identity, and adjusts default behavior so protected API endpoints return 401/403 instead of redirecting to login pages. That last change alone removes a classic SPA/API confusion that polluted logs and broke clients. (learn.microsoft.com)
On the diagnostics front, you can fine‑tune exception‑handler logging to suppress noisy telemetry for handled exceptions, and you’ll find improved tracing in Blazor scenarios. Taken together, you get fewer surprises in production and better visibility when they do happen. (learn.microsoft.com)
C# 14: quality‑of‑life wins you’ll feel in a day
C# 14 isn’t about splashy syntax; it’s about smoothing the edges. Field‑backed properties remove ceremony when you need custom accessors but still want an implicit backing field (via the field token). Extension members graduate beyond methods to properties and static members, making extension types a more complete design tool. You also get implicit Span<T> conversions, modifiers on simple lambda parameters, null‑conditional assignment, and partial constructors/events. These features reduce boilerplate and guide you toward safer, faster code. (learn.microsoft.com)
EF Core 10: modern data, less friction
If your data tier runs on SQL Server 2025 or Azure SQL, EF Core 10 adds first‑class support for the new JSON column type and SQL vector search APIs, plus named query filters and improved LINQ joins with new LeftJoin/RightJoin operators. For Cosmos DB, full‑text search joins existing vector capabilities for hybrid search patterns. The headline is simple: more expressive models with fewer hacks—and better performance paths for AI‑adjacent workloads. (learn.microsoft.com)
Will .NET 10 LTS break my app?
Probably not—but expect sharper edges where defaults got stricter. API endpoints protected by cookie auth now return 401/403 instead of HTML redirects; most API clients will thank you, but brittle tests may need updates. Identity and auth add new metrics and behaviors; validate your Observability pipelines. EF Core 10 requires the .NET 10 SDK/runtime and won’t run on .NET Framework, so multi‑TFM projects need a compatible plan. And while AVX10.2 support exists in the JIT, it’s disabled pending hardware—so you won’t be surprised by instruction‑set regressions. (learn.microsoft.com)
One more consideration: Microsoft extended STS (odd‑numbered) releases from 18 to 24 months starting with .NET 9. If you rode .NET 9, your end of support is November 10, 2026—the same day .NET 8 LTS sunsets. That synchronization is your signal to consolidate on .NET 10 LTS now and avoid a 2026 cliff. (infoq.com)
The 21‑Day .NET 10 LTS upgrade workplan
You don’t need a moonshot project. Run this play across three focused sprints and keep shipping.
Week 1: Prepare, branch, and prove it builds
• Create a short‑lived dotnet10 branch per repo and turn on a CI matrix that builds both your current target and net10.0. Keep tests running on both targets until cutover.
• Upgrade the SDK on build agents. Use global.json to pin 10.0 for the branch.
• Audit NuGet dependencies for .NET 10 support. Flag blockers early (EF providers, APM agents, native libraries).
• For GitHub Actions, review PR security settings; if you rely on pull_request_target, make sure your workflows are hardened before opening migration PRs. Our practical guide covers the Dec 8 policy change and safer patterns. Harden GitHub Actions pull_request_target.
Week 2: Migrate the hot paths first
• Move a representative API service and one background worker to net10.0. Enable ASP.NET Core’s new auth/Identity metrics and verify they land in your observability stack.
• Flip on passkey support in a non‑critical user flow if you’re already using Identity; validate enrollment and recovery paths.
• Try NativeAOT on a small CLI or function app—measure cold‑start and memory deltas. Capture before/after p95s for startup, request latency, and memory footprint.
• Adopt two C# 14 niceties where they reduce code noise: field‑backed properties for frequently‑touched domain types and an extension property block that removes a utility class.
Week 3: Data tier and rollout
• If you’re on SQL Server 2025/Azure SQL, test EF Core 10’s JSON columns and vector search on a sidecar service. If not, stick with conventional mappings; the benefit is optional, not a blocker.
• Switch your mainline services to net10.0, keep a fast rollback, and run a 48‑hour soak with autoscaling enabled. Watch GC pauses, thread pool starvation, and dotnet-counters for unexpected spikes.
• Clean up: remove dual‑targeting, update docs, and tag the release. Then set an upgrade cadence for minor 10.x patches.
C# 14: low‑effort wins you can ship today
Field‑backed properties are perfect when you want a custom setter but don’t want to declare a private field. Example: trimming user input or clamping values without ceremony. Extension members let you bundle related helpers on types you don’t own—no more scattering static “Utils.” The beauty is that these patterns are intuitive for reviewers and easy to adopt incrementally. If you use spans, the implicit conversions make performance‑oriented code less brittle. (learn.microsoft.com)
Try this micro‑refactor: replace a repetitive set of null‑checks with null‑conditional assignment in your orchestration code, or add an extension block to group your most‑used LINQ helpers. Your next PR will be smaller and clearer.
Security and compliance: move before Q1 2026
ASP.NET Core 10’s default API behavior (401/403 instead of HTML redirects) is a quiet security improvement—clients stop misinterpreting unauthenticated responses as successful 200s. Identity passkey support lets you pilot passwordless flows with standards‑based WebAuthn, which is where many organizations are headed next. On the crypto front, .NET 10 expands post‑quantum primitives and tightens JSON deserialization defaults (e.g., duplicate property handling). Whether or not you turn them on day one, landing on LTS gives you a clean baseline for 2026 audits. (learn.microsoft.com)
People also ask
How long will .NET 10 LTS be supported?
Through November 14, 2028, with monthly servicing and out‑of‑band security fixes as needed. Plan your next major refresh for mid‑2028 or earlier. (dotnet.microsoft.com)
Is .NET 10 LTS worth it for small teams?
Yes. The runtime and ASP.NET Core changes help every app class, and C# 14 removes day‑to‑day friction. Use the 21‑day plan and migrate service‑by‑service to keep risk low. If you’re on .NET 9 (STS), you’re time‑boxed to November 10, 2026 anyway—better to consolidate now. (infoq.com)
Do I need to change my authentication flow?
If you depend on cookie redirects from API endpoints, update expectations and integration tests; APIs now default to 401/403. If you use Identity, consider piloting passkeys behind a feature flag. (learn.microsoft.com)
Practical checklists you can copy
Adoption readiness (30 minutes)
• Confirm your target OS/container base images support .NET 10 runtime layers.
• Inventory NuGet packages and EF provider versions against .NET 10 compatibility pages.
• Validate your APM/metrics agent support matrix for .NET 10 and ASP.NET Core 10 new meters.
Performance sanity (60 minutes)
• Baseline: dotnet-counters monitor System.Runtime on your busiest service in production for 10 minutes.
• After migration: repeat and compare allocations/sec, thread pool queue length, and GC pause time.
• If allocations spike, scan for pooling behavior, especially around new memory pool eviction settings. (learn.microsoft.com)
Auth and API behavior (45 minutes)
• Add contract tests asserting 401/403 for protected API endpoints.
• If you use SPA redirects for web flows, ensure only browser routes see 302s; APIs shouldn’t.
• Pilot passkeys with 1% of traffic and monitor help‑desk tickets for recovery flows. (learn.microsoft.com)
Data highlights you can act on
• Release timing: .NET 10 LTS GA on November 11, 2025; servicing through November 14, 2028. (dotnet.microsoft.com)
• EF Core 10 adds JSON column mapping and SQL vector search support for Azure SQL and SQL Server 2025—useful if you’re building retrieval or semantic ranking into your app. (learn.microsoft.com)
• The SDK’s file‑based apps can publish to native executables; combine with NativeAOT for CLIs and serverless cold‑start improvements. (learn.microsoft.com)
When not to upgrade right away
If you rely on libraries that aren’t yet compatible—or you’re mid‑peak season—pause. Keep a net10.0 branch building to surface issues, upgrade one non‑critical service, and revisit in January. Don’t force risky cutovers during revenue‑critical windows. For high‑compliance environments, proof your observability first; ASP.NET Core’s new metrics are a net positive, but only if they’re wired into dashboards your on‑call team actually uses. (learn.microsoft.com)
Where our team can help
If you want a structured migration with guardrails, we’ve published hands‑on playbooks specifically for this release: start with The .NET 10 LTS Playbook and our production upgrade checklist. If you need a steady partner for a multi‑app program, see our modernization services or just reach out. We’ve done this dance across stacks and sectors.
What to do next
• Spin up a net10.0 branch, enable dual‑target CI, and baseline performance before you touch code.
• Migrate one API and one worker to validate auth, metrics, and deployment tooling.
• Adopt two C# 14 features where they reduce code, and try NativeAOT on a CLI.
• If you’re on SQL Server 2025/Azure SQL, test EF Core 10 JSON and vector search in a sandbox.
• Set a date to cut over your mainline services, then remove dual‑targeting to keep the build lean.
Zooming out, .NET 10 LTS is the stability milestone that also buys you speed and safer defaults. If you upgrade with intent, you’ll spend fewer cycles firefighting and more time shipping.
