diagrams.net is open source, online, desktop and container deployable diagramming software

GSuite and Google Drive

Works with Google Drive and G Suite. Use add-ons for Docs, Sheets and Slides.
Example diagram
Sharepoint and OneDrive

Works with OneDrive and Sharepoint. Office 365 app for Word, Powerpoint and Excel.
Example diagram
Atlassian

Highest-rated Confluence app in the Atlassian Marketplace*. Works in Jira too.
Example diagram
Git and Dropbox

Works with Github, GitLab and Dropbox for visual documentation in distributed teams.
Example diagram
Desktop

Download diagrams.net Desktop for offline use on Windows, macOS, Linux and ChromeOS.