List of open source applications built with React.js
https://github.com/CompuIves/codesandbox-client - Client for the CodeSandbox website.
https://github.com/freeCodeCamp/freeCodeCamp/
https://github.com/rsimmons/voracious - A video player for language learning that allows to easily create Anki Flashcards.
https://github.com/Khan/perseus/tree/master/src
https://github.com/withspectrum/spectrum
https://github.com/opencollective/opencollective-frontend
https://github.com/fkling/astexplorer
https://github.com/excalidraw/excalidraw/
https://github.com/Automattic/wp-calypso
https://github.com/eggheadio/egghead-next - New Version of Egghead, built in Next.js
https://github.com/zeit/next-site
https://github.com/fbsamples/f8app
https://github.com/artsy/force
https://github.com/reactjs/reactjs.org
https://github.com/devhubapp/devhub
https://gitlab.com/gnaar/powder
https://github.com/mattermost/mattermost-webapp
https://github.com/oldboyxx/jira_clone
Credits:
https://www.reddit.com/r/reactjs/comments/atq0uh/what_are_some_nice_open_source_reactjs_production/
https://www.reddit.com/r/reactjs/comments/igrpdr/are_there_any_large_open_source_repos_out_there/