No account needed — the photo stays in your browser while you mark it. JPEG or PNG, shot straight-on or at an angle.
Best results: include a known-size rectangle in frame — a sheet of A4, a target backer, a printed grid — so the next step can correct for angle and scale. When your results are ready we save the group and a corrected, metadata-free copy of the photo so you can share it or claim it later — privacy policy.