💡 Our Technical Review in summary
Summary
- Microsoft is updating the technical requirements for Teams on the web to ensure security and performance.
- Beginning May 15, 2026, all browsers used to access Teams on the web must be compliant with ECMAScript 2022 (ES2022) standards.
- Currently supported versions of Microsoft Edge, Google Chrome, Mozilla Firefox, and Safari already meet these standards.
- This change is mandatory and cannot be disabled by administrators.
Impact
- User Access: Users on non-compliant or “out of vendor support” browsers will be blocked from accessing Teams on the web starting May 15, 2026.
- Banners: From now until May 14, 2026, users on unsupported browsers will see reminder banners during their sessions.
- Scope: This update only affects the web version of Teams; the Teams desktop application and mobile apps are not impacted.
- Conditional Access: Organizations using Conditional Access policies may see authentication failures if users attempt to sign in via unsupported browser environments.
- Legacy Systems: Any devices still running legacy browser versions that no longer receive security updates will lose access to Teams functionality on the web.
Action Required
- Inventory Browsers: Conduct an audit of browser versions across your organization’s endpoint fleet to identify any installations that are out of vendor support.
- Update Enforcement: Ensure all managed devices are updated to the latest stable versions of Microsoft Edge, Google Chrome, Firefox, or Safari.
- Policy Review: Verify that your Endpoint Management policies (such as Intune or Group Policy) are set to keep browsers updated automatically.
- Support Readiness: Brief your helpdesk and IT support staff on the May 15, 2026, enforcement date to prepare for potential “access blocked” inquiries from users on older hardware or software.
- Communication: Proactively notify users who may still be utilizing older browser versions to update their software before the deadline to avoid service disruption.
Microsoft Official Update
Service: N/A
Category: planForChange
Severity: normal
Introduction
To maintain security, performance, and long-term compatibility, Microsoft Teams on the web will require modern browser standards. Beginning May 15, 2026, Teams on the web will only be supported on browsers that are compliant with ECMAScript 2022 (ES2022).
When this will happen
- Now through May 14, 2026: Users on unsupported browsers will see reminder banners.
- Beginning May 15, 2026: Teams on the web will be blocked on non-compliant browsers.
How this affects your organization
Who is affected:
- All tenants using Teams on the web
- Users accessing Teams through unsupported browser versions
- IT administrators responsible for browser standards and endpoint management
What will happen:
- Reminder banners will appear before enforcement.
- Blocking page will appear starting May 15, 2026 until the browser is updated.
- The change is enabled by default and cannot be disabled.
- Desktop and mobile Teams clients are not impacted.
What you can do to prepare
- Inventory browser versions used to access Microsoft 365 web apps.
- Ensure users are on supported browsers and versions.
- Notify helpdesk staff and end users ahead of enforcement.
Browser compatibility guidance
All currently supported versions of Microsoft Edge, Google Chrome, Mozilla Firefox, and Safari are ECMAScript 2022 (ES2022) compliant. Browsers that are out of vendor support should be assumed non‑compliant. A browser is considered “out of vendor support” when its publisher no longer provides updates or security fixes; these browsers should be assumed unsupported for Teams on the web.
Compliance considerations
Conditional Access policies may be impacted if users attempt access with unsupported browsers.
