Is there a way to delete all structures?

[doctore_gonzo]

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[Zigamus Wizard]

If they are blueprints it goes much faster, otherwise there are mods that help with mass building and mass deleting.

[Kage Goomba]

https://satisfactory-calculator.com prob would be better

[Jay and Silent Rob]

If you're cool with editing your save, loading it on the aforementioned satisfactory calculator sight, selecting all of the structures on the map, and deleting them is possible. You're also given the option to place all materials in crates that will spawn around your saved position or to just wipe it all. You gotta be careful with the crates because if you have nuclear facilities running the entire area will be maxed out on radiation, and if you have a lot built it can take ages to unpack all of the crates, even if you make sure to be in the middle of a big item bank that sorts everything you throw into it.

I recommend going through your bases and building awesome sinks for every production line and draining every single machine, every belt, and every storage container before doing any mass-deletion, and that goes for both in-game mass deletion and for save edit tools.