Swap and Stack

In vanilla Minecraft, pressing F always swaps the items in your main hand and off-hand — even when both hands hold the exact same item. If you're holding 20 torches in one hand and 30 in the other, hitting F just flips which hand has which stack instead of combining them into one.

Swap and Stack fixes this.

When both hands hold the same item (same enchantments, same NBT/components), pressing F now merges the stacks together, up to the item's max stack size — just like dragging one stack onto another in your inventory. If the items are different, F still works exactly like vanilla: a normal swap.

Want the old behavior back for a moment? Hold Shift while pressing F to force a normal vanilla swap, even if both hands hold the same item.

How it works

• Same item, fits in one stack → both stacks combine into the off-hand.
• Same item, doesn't fully fit → off-hand fills up to max stack size, the rest stays in the main hand.
• Off-hand already full, nothing to merge → falls back to a normal swap, so pressing F never feels like it did nothing.
• Different items, or an empty hand → works exactly like vanilla Minecraft, no changes.
• Holding Shift → always does a normal vanilla swap, regardless of what's in your hands.

No new items are created — this only rearranges what you're already holding.

Notes

• No config needed, no new keybinds. Uses the same F key you already use.
• Doesn't affect items that can't stack (tools, weapons, armor) — those still swap normally.

Compatibility

Doesn't touch inventory GUIs, item registries, or other mods' items — it only changes what happens when the vanilla hand-swap action fires. Should be compatible with virtually everything.