Technical Tip: Recommended release for FortiOS

Description

This article exists to help users determine the most appropriate software release for FortiOS. The recommendations stated below are the latest as of June 2026 and are reviewed and updated every quarter.

The information in this document is not meant to be exhaustive and is intended to serve as general guidance to customers, especially in cases of mass deployments/upgrades. When working with Fortinet SEs, Professional Services, or TAC: it is important to refer to their specific guidance.

An additional information section has been added to the bottom of this article for answers to common questions.

Subscribe to the RSS feed by selecting the three-dotted menu button to keep up to date on the latest changes to this article (note that this feature is temporarily unavailable as of June 2026).

Scope

This document is a general recommendation of FortiOS software for general customer deployments for general stability and is updated quarterly.

For customers who may be leveraging the latest features, the latest FortiOS versions may be more applicable.

Solution

Engineering special builds:

In certain cases, critical bug fixes are made available on Engineering special builds. These builds are not available on support.fortinet.com. If any issues are encountered specific to the environment which is not already fixed in existing releases, contact Fortinet TAC Support to investigate the issue.

Special builds are meant to be deployed for a limited time frame and customers are advised to move to the next maintenance build with their fixes as soon as it is available. Engineering special builds are fully supported by the Fortinet Advanced Support team and, in some specific instances, by Fortinet TAC Support.

Note:

AC and DC models use the same firmware image.

FAQ:

1. What to take into consideration when deciding on the release to use:

   • Review the latest release notes to check if any known issues could impact the deployment.

   • Subscribe and Review relevant PSIRT notifications:
     FortiGuard Labs - RSS Feeds

2. What is taken into consideration for a Recommended Release:

   • Typically Recommended Releases are also labeled as 'Mature' releases.

   • Significant field deployment of 40,000 or more FortiGates that have installed the recommended build.

   • No high-severity vulnerabilities that are without mitigating steps or workarounds.

3. How often the Recommended Release KB article is reviewed:

   • The Recommended Release KB article is reviewed and updated quarterly.

4. Why some platforms differ in releases:

   • New platforms may be on initial New Product Introduction release and will have GA builds in a staggered process after FortiOS GA has been released.

   • Older products may not support the latest recommended FortiOS release and hence the recommended release will be the latest FortiOS the device can support.

5. How to keep up with the latest updates on this article:

   • In the top right corner of the article, select the three-dotted menu button and select 'Subscribe to RSS Feed' (note that this feature is temporarily unavailable as of June 2026).

   • Or login to the Fortinet Community Account and in the top right corner of the article, select the three-dotted menu button and select 'Subscribe'. An email will be received when this page is updated. (Note that this feature is temporarily unavailable as of June 2026.)

Related article:
Technical Tip: Recommended Release for FortiManager and FortiAnalyzer