When using a web browser, tabs line up across the top in the order they were opened. The earliest tab appears on the left, with each new one added sequentially to the right.
This lineup persists through browsing. New tabs join the end, and switching among them keeps the established sequence intact, with no break in the display.
Upon returning to the tab bar, the arrangement has shifted. Tabs now cluster by website domain or content similarity, pulling related ones together irrespective of their original positions.
The sequence tied to opening order no longer holds. Tabs once spaced by creation time now sit adjacent within groups, altering the overall lineup.
The tab bar continues to function, but its organization reflects a new basis that took hold without markers or signals.