Microsoft is retiring the legacy IDCRL authentication protocol in SharePoint Online and OneDrive for Business by May 1, 2026, enforcing modern protocols OpenID Connect and OAuth. Legacy authentication will be blocked starting February 16, 2026, with temporary re-enablement until April 30, 2026. Organizations must migrate promptly.
Applies to: SharePoint Online · Microsoft OneDrive
Source: mc.merill.net — data via Merill Fernando's open archive (MIT).