Microsoft urges migration to .NET 10: support for .NET 8 and .NET 9 ends in 2026

What happened?

Microsoft has set November 10, 2026 as the end-of-support date for .NET 8 and .NET 9 platforms. From that day onward, the company will stop issuing security updates, bug fixes, and technical support for both versions. This was communicated by Rahul Bhandari, senior program manager at Microsoft, in a blog post published on June 29, 2025.

.NET 8, released on November 14, 2023, is an LTS (long-term support) version that originally would receive support for three years, but Microsoft has decided to unify the lifecycle of recent versions. .NET 9, released on November 12, 2024, is an STS (standard-term support) version with a shorter cycle. Both will become unsupported simultaneously.

This decision breaks with Microsoft's tradition of offering extended support for LTS versions. Historically, .NET Core 3.1 (LTS) had support until December 2022, while .NET 5 (STS) ended in May 2022. With .NET 8 and 9, the company accelerates planned obsolescence, forcing developers to adopt newer versions. This reflects a strategy of continuous innovation but also increases pressure on businesses to keep their applications updated.

Why is it important?

Migration to .NET 10 is critical for several reasons:

• Security: Applications remaining on .NET 8 or .NET 9 will not receive security patches, making them vulnerable to exploits and attacks. According to Microsoft's 2024 vulnerability report, 60% of successful cyberattacks exploit known unpatched vulnerabilities.
• Technical support: Microsoft will not offer assistance for technical issues on these versions. This can leave businesses without resources for critical failures.
• Compatibility: Visual Studio 2022 will mark .NET 8 and .NET 9 components as “unsupported” in a future update, which could generate warnings or blocks in the development environment. Additionally, third-party libraries like Entity Framework Core and ASP.NET Core will stop updating for these versions.

Moreover, .NET 10 is an LTS version with support until November 2028, providing long-term stability for enterprise projects. Microsoft has announced that .NET 10 includes an optimized runtime with performance improvements of up to 20% in I/O operations, and new integrated artificial intelligence capabilities, such as native support for ONNX models and GPU acceleration.

Historical context shows that Microsoft has been shortening support cycles. For example, .NET Framework 4.8 (released in 2019) still has support until 2030, but modern .NET Core/.NET versions have shorter cycles. This forces businesses to plan migrations every 2-3 years, increasing operational costs but also accelerating adoption of new technologies.

What consequences will it have?

Businesses and developers who do not migrate before the deadline will face:

• Increasing security risk from not receiving critical updates. A 2023 Ponemon Institute study estimates the average cost of a data breach from unpatched vulnerabilities is $4.45 million.
• Inability to obtain official Microsoft support, which can delay resolution of critical production issues.
• Compatibility issues with modern tools and libraries that stop supporting .NET 8/9. For example, Azure Functions and Azure App Services have already announced they will stop supporting .NET 8 after November 2026.

On the other hand, migration to .NET 10 brings performance improvements, new AI features, and an optimized runtime, according to Microsoft. In internal tests, Microsoft claimed that .NET 10 reduces memory consumption by 15% in web applications and improves startup speed by 30%.

Compared to previous events, such as the end of support for .NET Core 2.1 in 2021, many companies postponed migration and suffered security incidents. For example, in 2022, a critical vulnerability in .NET Core 2.1 (CVE-2022-30184) affected unpatched applications, causing data breaches in several logistics companies. Microsoft expects developers to act more proactively this time.

What should readers know?

The upgrade process is straightforward: simply change the TargetFramework property in the project file to net10.0 and update development and hosting environments. Microsoft has published a detailed guide titled “Upgrade to a new .NET version” in its official documentation. However, developers should verify the compatibility of their dependencies, as some third-party libraries may not have versions for .NET 10.

It is important to note that applications compiled with .NET 8 or .NET 9 will continue to run after end of support, but without security guarantees or assistance. Microsoft strongly recommends not delaying migration. Additionally, companies using Docker containers must update base images to .NET 10, as .NET 8/9 images will stop receiving updates.

“By upgrading, you will continue to receive security updates and service fixes to keep your applications protected,” said Rahul Bhandari.

To download .NET 10, developers can visit dotnet.microsoft.com. Microsoft also offers analysis tools like .NET Upgrade Assistant to facilitate migration.

Looking ahead, .NET 11 is expected in November 2026, suggesting an annual release cadence from Microsoft. This implies that businesses must adopt a continuous update strategy to avoid falling behind. According to Gartner, by 2027, 80% of enterprise applications based on .NET will use LTS versions released in the last two years.