The website is written with Jekyll markdown.
For small changes, you can use the edit button at the top right of each page.
For larger changes, you can run:
$ ./gradlew :website:serveWebsite
Which will start a docker container and serve the website to http://localhost:1313. After one hour, the docker container will exit and you will need to re-start it.
You can also check links with:
$ ./gradlew :website:testWebsite
Pull requests with website changes will automatically be staged to GCS. The URL is at the end of the console logs for beam_PreCommit_Website_Stage_GCS_Commit, and is of the form http://apache-beam-website-pull-requests.storage.googleapis.com/{PR_NUM}|/index.html