Before a page goes live, every visible piece of text on it is measured against the colour behind it, every image is checked for a text alternative, the heading outline is checked for skipped levels, every form field is checked for a real label, and every link is checked for meaningful wording.
That check runs at three screen widths — a desktop, a tablet and a phone — and it is run again on the published page, not only on a preview of it.
We have not yet commissioned an independent accessibility audit, and we do not claim a formal certification. When we do, we will say so here and publish what it found.