Crosspath

A crosspath is the combination of upgrade paths you buy on a tower. Every BTD6 tower has three upgrade paths with five tiers each, but you can only use two of them, and only one can go past tier 2. Crosspaths are written as three numbers, one per path, so 2-0-4 means two upgrades in the top path, none in the middle and four in the bottom path.

Almost every guide, including ours, uses this notation, so learning to read it makes every strategy easier to follow.

How to read crosspath notation

The three numbers are always in the same order: Top path – Middle path – Bottom path.

• 0-0-0 is a base tower with no upgrades.
• 2-0-4 has tier 2 in the top path and tier 4 in the bottom path.
• 0-3-2 has tier 3 in the middle path and tier 2 in the bottom path.
• 5-2-0 is a tier 5 top path tower with two middle path upgrades, the most a tower can have.
• An x means that path does not matter for the point being made. "Any x-x-4 Monkey Village" means the bottom path at tier 4, whatever else it has.

For example, a Heli Pilot with Apache Prime (top path tier 5) and Bigger Jets (middle path tier 1) is a 5-1-0.

The crosspath rules

1. Each tower has three paths with five tiers each.
2. You can upgrade only two paths. As soon as you buy upgrades in two paths, the third path locks. One of the three numbers is always 0.
3. Only one path can go past tier 2. Once one path reaches tier 3, the other path is capped at tier 2.
4. The maximum is 5-2-0 or any arrangement of it, such as 0-2-5 or 2-5-0. That is seven upgrades in total.
5. Only one of each tier 5 upgrade. In a normal game you can only own one copy of each specific tier 5 upgrade at a time.

Codes like 3-0-3 or 4-1-1 are impossible: the first has two paths above tier 2, the second uses all three paths.

Why the second path matters

Your main path decides what a tower is: a MOAB killer, a crowd clearer, a support tower. The second path, usually tier 1 or 2, decides how well it does that job. Tier 1 and 2 upgrades are cheap, and they often add exactly what the main path lacks:

• Camo detection. A Sniper's Night Vision Goggles (0-1-0), a Dart's Enhanced Eyesight (0-0-2) or an Ice Monkey's Cold Snap (2-0-0) can fix a tower's blind spot for little money. See Camo.
• Lead popping. Full Metal Jacket (1-0-0) on a Sniper or Red Hot Rangs (0-0-2) on a Boomerang Monkey. See Lead.
• Pierce or damage. Sharp Shots and Razor Sharp Shots (1-0-0 and 2-0-0) give the Dart Monkey more pierce.
• Range and attack speed. Many towers have a cheap range or speed upgrade on one path that improves the main path a lot.

The wrong crosspath can lock you out of something you need later. Since the third path closes the moment you upgrade two paths, decide your crosspath before you buy that first secondary upgrade.

Common crosspaths worth knowing

• 2-x-0 Dart Monkey with middle path: Razor Sharp Shots is the usual crosspath for Triple Shot and above, adding pierce to every dart.
• 2-2-0 Dart Monkey before a Fan Club: extra pierce makes the transformed Dart Monkeys much stronger.
• 1-1-0 Sniper Monkey: Full Metal Jacket plus Night Vision Goggles, a very cheap way to pop early Camo Leads.
• 0-2-3 Mortar Monkey: Signal Flare with the middle path, a reliable de-camo option.
• 0-2-0 Monkey Village: Radar Scanner, Camo detection for every tower in range.
• 0-3-0 Monkey Village: Monkey Intelligence Bureau, letting towers in range pop every bloon type.
• 0-3-0 Bomb Shooter: MOAB Mauler, the classic first MOAB answer before round 40.

Exact best crosspaths change with updates and with the map, so check each tower's page in our Pedia, where our guides list the crosspaths we actually use.

Upgrade order tips

• Buy the cheap secondary upgrade early if it solves an immediate problem, such as Camo detection before round 24.
• Otherwise rush the main path to its power spike, then add the crosspath.
• Primary Expertise (5-0-0 Monkey Village) gives Primary towers in its radius their tier 1 and 2 upgrades for free, which makes those cheap upgrades, crosspaths included, free for those towers.
• Use upgrade hotkeys in competitive modes like Races, where opening the upgrade panel counts as pausing.

Paragons and crosspaths

Paragons go beyond the crosspath system. They are a separate upgrade above tier 5 that needs tier 5 towers of the same type, so they do not use crosspath notation at all.

Frequently asked questions

What does 2-0-4 mean in BTD6?

It means a tower with two upgrades in the top path, none in the middle path and four in the bottom path.

Can you have two tier 5 paths on one tower?

No. Only one path can go past tier 2, so the most you can have is something like 5-2-0.

Can you upgrade all three paths?

No. As soon as you upgrade two paths, the third one is locked.

What is the best crosspath for a tower?

It depends on what the tower lacks. Usually it is the cheap tier 1 or 2 upgrade that adds Camo detection, Lead popping, pierce or range to your main path.

Can I change a crosspath after buying it?

Not directly. Upgrades cannot be removed, so you would have to sell the tower and build it again.

Why can't I buy a second tier 5 upgrade?

In a normal game you can only have one of each specific tier 5 upgrade at a time. Build a different tier 5 or wait until you have sold the first one.