Nesting in LightBurn: what Nest Selected really does, and when it breaks

LightBurn has no built-in nesting engine; the developers have said so on their own forum, and auto-nesting remains a long-standing feature request. What LightBurn 2.x has instead is Nest Selected, and it is a hand-off: your shapes leave LightBurn as an SVG, get nested on a third-party website, and come back by import. Once you know that, every failure mode people hit makes sense.

What Nest Selected actually is

The official LightBurn documentation describes the mechanism plainly: the command exports your selected shapes to LightBurnNest.svg and opens svgnest.com, the free open-source nesting site, in your default browser. The nesting itself, sheet size, spacing, rotations, run time, all happens on that website. When you are happy with the layout you download the nested SVG and import it back into LightBurn.

There is nothing wrong with that design in principle. SVGnest was a good tool. The problem is the tense: its repository has had no commit since April 2019, so LightBurn's nesting button effectively points at software frozen six years ago.

The failure modes, and where they come from

The page breaks on negative coordinates. If your LightBurn shapes sit left of or above the origin, the exported SVG carries negative coordinates, and svgnest.com's interface chokes on them. When this hit users in April 2025, the answer in the LightBurn forum thread was blunt: SVGnest has not been updated in six years. The workaround is on your side: move everything into the positive quadrant, near the origin, before you export.

It runs forever, by design. SVGnest's genetic algorithm has no stopping condition; the README says to stop it when you are satisfied. On hard inputs the first good candidate can take a very long time to appear: issue #55 describes 20-minute runs with nothing to show. If utilization has not improved for a few minutes, stop it and take what it has.

Overlaps at higher part counts. Issue #77 reports overlapping parts in a 150-part nest. Nothing re-checks the layout, so inspect it yourself before cutting, especially where parts almost touch.

Curves come back as polygons. SVGnest approximates all arcs and beziers with straight segments at a set tolerance. Your round holes return as many-sided polygons, which you will see in engraving quality and file size.

Not everything gets exported. The hand-off exports your selected shapes; shapes sitting inside a container shape are not exported. Count your parts on the website before you invest run time.

A clean SVG round trip you control

The round trip itself is sound, so keep it and swap the weak leg. The workflow that avoids the traps:

1. In LightBurn, move your parts into the positive quadrant near the origin, and give each cut layer its own color as usual.
2. Select the parts and export them as SVG (File, then Export).
3. Nest in the external tool of your choice. Set the sheet to your real material size and set the spacing to your kerf plus the clearance you want between parts.
4. Import the nested SVG back into LightBurn. Measure one known dimension immediately; SVG unit handling differs between tools, and a scale error caught now costs nothing.
5. Check the layer assignments. LightBurn maps imported colors to cut layers, so confirm your cut and engrave layers survived the trip before you press start.

That checklist works with any nester that reads and writes SVG, including svgnest.com on its good days.

Swapping the svgnest.com leg for something maintained

NestForge does the same job as the svgnest.com leg of that round trip, SVG in, nested SVG out, and the honest framing first: it is a separate tool, not a LightBurn plugin. The round trip stays manual, export, nest, re-import, exactly as above.

What changes: runs terminate on their own with a deterministic result instead of running until you give up. Arcs are preserved end to end, so round holes are still round when they land back in LightBurn. Every layout is checked by an independent exact-arithmetic validator before you see it, so the overlap-you-find-after-cutting failure mode is gone. And it runs offline in your browser, no website that can break while you have a deadline. It also reads DXF directly, parsed locally, if your parts come from CAD. The free tier covers up to 10 parts on 1 sheet with no time limit, which is enough to test the whole round trip against your own LightBurn workflow before deciding anything.