Actually, Firefox version numbers were totally independent for most of their history, but Mozilla recently adjusted them to roughly align with Chromium versions to reduce confusion for developers.

2004 - Firefox 1.0, no Chrome yet 2010 - Firefox 4.0, Chrome around version 8 2011 - Firefox switches to rapid releases 2020 - Firefox and Chrome both around version 85, just by coincidence 2024 - Firefox jumps from 124 to 126 to align with Chrome 126 2025 - Firefox 126+, Chrome 126+, version numbers now track similarly