Hi. Firefox developer speaking here. Feel free to take a look at https://wiki.mozilla.org/Release_Management/Release_Process and https://aosabook.org/en/ffreleng.html. The latter is quite outdated but some core assumptions are still valid. Our CI is hosted at https://treeherder.mozilla.org/jobs?repo=autoland . Every patch that is uploaded will be tested before and after it goes into a branch. Firefox Nightly ships directly from that branch. The changes will be "promoted" to Beta (and subsequently Release) every four weeks. Our community hangs out on Matrix and is very Open to newcomer questions and other contributors. In fact, we Vene have an introduction channel and list good first bugs on bugzilla (searchable through something called "Codetribute")