Title link generation change
Google began rewriting search result titles using on-page text such as H1s rather than relying on the title element.
What changed
In August 2021 Google changed how it generates the clickable title in search results, drawing more often on main headings, anchor text and other visible page text instead of the title element. After publisher complaints Google published an explanation and later said the original title tag was still used in the large majority of cases. The change made title elements a strong hint rather than a guaranteed output. The rewrite was noticed in mid-August; Google's explanatory post followed on 24 August.
Timing
Announced on 24 August 2021, with rollout beginning 1 August 2021. No completion date was announced. Rankings typically remain unstable for the whole rollout window, so measurements taken inside it are not a reliable read on the outcome.