Microsoft is testing AI-powered summaries in Windows Notepad, currently being rolled out to Windows Insiders in the Canary and Dev channels. The 'Summarize' feature allows users to generate concise summaries by highlighting text and selecting 'Summarize' or using the Ctrl + M shortcut. A Microsoft account is required, and Microsoft 365 subscribers will use AI credits for this feature. Users can disable AI features if they prefer the classic Notepad experience. Additionally, Notepad will include a 'recently closed files' feature for quick access to previously closed documents.