Every measurement, kept, stamped, and yours to take
Each scan is a dated record: the score, the grade, every check's result on every measured page, and the exact engine version that produced it. The history is the product's memory and your evidence.
A record, not a redraw
Scans are never overwritten. Each one keeps its full results as they were produced, for as long as the site is watched, so what your site scored in March is still readable in November exactly as March measured it.
Stamped with the engine that ran it
Rules change: checks are added, weights move, engines rescore. Every scan carries the engine version that produced it, which is what makes an old number meaningful instead of merely old, and what lets the product refuse to compare numbers two different rulers drew.
Moves, told honestly
Beside each score, the history shows the move against the previous scan by the same engine. Where the engine changed, the row says that instead: a site is never drawn as getting worse because the ruler got stricter.
Take it with you
The history downloads as CSV in one click: every scan with its date, trigger, status, score, grade, engine version and page count. For a report, an audit, or the argument you are having with somebody who claims the site was always like this.