Three.js scenes are GPU-heavy and the cut ribbon grows as the simulation plays. Memory use is normal up to ~500MB on a 2000-line job. If your browser tab is using 2GB+, that's a leak — please report it here with browser + OS info + the shape that triggered it.
Workaround: reload the page, which resets everything. Don't leave the tool open with no part loaded for hours.
Workaround: reload the page, which resets everything. Don't leave the tool open with no part loaded for hours.