How do I craft a balancer part?

By default each Belt Balancer part costs 4 iron plates, 2 iron gear wheels, and 2 transport belts (1 second to craft). A startup setting, Balancer part recipe, offers alternatives from a cheaper version up to belt- and splitter-based recipes. Every option substitutes sensibly in overhaul packs: an ingredient is only used if it exists in your game.

What research do I need?

One technology, Balancers, unlocked right after Logistics (the yellow-belt research). Its cost matches whatever Logistics costs in your game, so it stays reasonable in overhaul mods too. A startup setting, Balancer research cost, can move it to Logistics 2 or Logistics 3 instead; the cost and its place in the tech tree both follow the chosen tier.

How do I build a balancer?

Place parts next to each other in any shape, then run belts into and out of the edges. A belt pointing in is an input, a belt pointing out is an output. Each part connects to one belt, so a 4-input, 4-output balancer is eight parts: a column of four carrying the inputs and a column of four carrying the outputs. Parts with no belt against them are fine; they just join the shape. Laying a second belt against a part that already has one is refused with the reason on screen, and the belt goes back to your inventory. The balancer itself has nothing to configure.

How big can a balancer be?

Any shape, up to 64 belt connections per side (64 inputs and 64 outputs). Since each part carries one belt, a balancer needs at least as many parts as it has belts.

Why one belt per part? It used to allow more.

Factorio 2.1 fixed the engine behaviour that let several of this mod's hidden belt interfaces share one tile, so on 2.1 every balancer part connects to exactly one belt. On Factorio 2.0, a map setting (Allow multiple belts per balancer part, off by default) restores the old compact layouts. A 2.0 save that already uses them keeps working: the mod turns the setting on for that save at first load and says so in chat. Turning the setting off while such balancers are standing is refused, with a chat message listing every one of them as a clickable map ping. Keep in mind that multi-belt layouts cannot exist on 2.1 at all, so builds that rely on the setting will need rebuilding if the save ever moves to 2.1.

What happens to my save when I upgrade from Factorio 2.0 to 2.1?

Update this mod together with the game (2.1 clients are offered the 2.1 release automatically). On the first load, every balancer built one belt per part keeps working as-is. Balancers using multiple belts per part cannot run on 2.1: their parts and belts stay where they are, whatever items they held are placed on the ground beside them, and each force gets one chat message listing every affected balancer as a clickable map ping, with the map revealed around each one. Rebuild them one belt per part and they come back. One warning: never load and then save the map with the mod missing entirely -- Factorio deletes a missing mod's entities, and that loss is permanent.

What is the biggest balancer actually tested?

A 64 input, 64 output balancer (about 1,150 internal components) was benchmarked saturated with express belts: every one of the 64 outputs delivered 99.2% of a full express belt, balanced to within 0.3% of each other. Smaller shapes (4x4, 8x8, 9x9, and asymmetric ones like 3 to 5) deliver full belt throughput per output with a spread of 0.15% or less. A stress save with 404 balancers running at once, including that 64x64, showed effectively zero ongoing script cost.

Does it actually balance under weird conditions?

Yes, and this is the mod's main advantage over chest-based balancers. If only one input is fed, every output still gets an equal share. If an output is blocked, its share redistributes to the others. A slow belt on one output does not throttle the rest.

What happens to items inside when I edit or remove a balancer?

Editing a running balancer (adding or removing a belt or part) keeps the items inside the machine; nothing spills. Mining a part or an attached belt puts whatever the balancer can no longer hold into your inventory, like mining a vanilla machine. Items are never deleted.

Does it work with Space Age and Quality?

Yes. Balancers work on space platforms, stacked belts come back stacked after edits, mixed-item (sushi) belts are handled, and parts built at higher qualities work normally.

Does it keep up with faster belts from other mods?

Yes. The balancer's internals match the fastest belt any installed mod defines, with no cap, so modded belts above vanilla speeds are never throttled. (In the base game and Space Age its internals already run well above turbo belts, so nothing changes there.)

Can I migrate from Belt Balancer 2 or 3?

Yes. Uninstall the old mod with this one installed and every old balancer part in your save is converted automatically on the next load, keeping its position, health, and quality. Your old blueprints and item stacks keep working. On Factorio 2.0 the converted balancers keep running (the multiple-belts setting turns on for that save automatically). On Factorio 2.1, converted balancers built one belt per part run immediately; ones with several belts on a part get the same rebuild checklist described above. The only loss is the handful of items the old mod held in its internal buffer (up to a few per balancer), which cannot be recovered.

Does it slow down my game?

A finished balancer runs no script at all. Balancing is done by real (hidden) splitter entities the game engine simulates natively, so the per-tick cost is close to zero. In head-to-head benchmarks it is roughly 45x cheaper per balancer than Belt Balancer 2/3.