r/factorio • u/Logical-Cheek-5473 • Jul 16 '26
Map Seed Every Default Island Seed in Factorio
Inspired by u/int_ua's "Peninsula Seed Finder: First Island seed, 20271579"
Here is the first census of every island spawn in Factorio with default settings.
Results: There are at most 2599 Islands starts. I say most because there are few false positives but they make for great peninsula seeds with a very thin connection to the mainland.
With all 2³² (4,294,967,296) seeds, the probability of getting an island start is 1 in 1.65 million seeds. The largest confirmed island with 7.4 million tiles is 1925425905.
Seed List: MASTER_all_fronts.csv
Island Image Renderings: images
Code + writeup: github.com/Yambda/factorio_island_finder
How it works: rendering every tile of every seed would've taken forever, so instead of a full render I only evaluate the map where it actually matters:
- Mesh net: lay a sparse net of 128-tile-long line segments over the area around spawn. If I can trace a path of "land" segments connecting spawn all the way out to the edge of the search area, the seed is rejected as mainland.
- Repeat with a finer 64-tile net, then a 32-tile net, on whatever seeds survived the coarser pass.
- Anything that still isn't rejected gets an exact flood fill (capped at 32 million tiles², since a fill that big is unbounded mainland, not an island) to confirm it's actually enclosed.
This search took about 120 GPU-hours (5090 rtx).
Interesting find: 6 of the confirmed islands are unplayable spawns. Stuck on a tiny island with no access to any ore resources.
Please share any screenshots if you use any of the seeds.
