Interactive 3-Way Switch Wiring Diagram
A 3-way switch wiring diagram shows two 3-way switches controlling one light. One switch takes the hot feed on its COM terminal, the other sends the switched hot to the light from its COM terminal, and two traveler wires run between the pairs of brass terminals. Pick a layout below, flip each switch and watch the energized wires change. Turn the breaker off and verify with a tester before you open a switch box.
Choose a layout and flip the switches
The light is on: both switches have chosen the same traveler.
Power from the breaker enters the first switch box. A 3-wire cable carries the two travelers and the neutral to the second switch, and a 2-wire cable runs from there to the light. A neutral is present in both switch boxes.
Wire colours and roles
-
- White: neutral
- Black: hot (line) feed
- Black: traveler
- Red: traveler
- Black: switched leg to the light
- Bare copper or green: equipment ground
-
- Black: hot (line) feed
- White: neutral
- White re-identified with amber tape: hot
- Black: switched leg to the light
- Black: traveler
- Red: traveler
-
- White: neutral
- Black: hot (line) feed
- Black: traveler
- Red: traveler
- Black: switched leg to the light
An amber glow marks a conductor that is carrying power in the current switch positions. Terminal markers: dark = COM, gold = traveler, green = ground. Colours are conventions: identify real conductors by testing, never by colour alone.
What is connected where
Pick a layout above. The table for that layout is shown below, so the diagram is also available as text.
Power at the first switch
| Box | Conductor | Connects to |
|---|---|---|
| Switch 1 | Black hot from the breaker | Dark COM screw |
| Switch 1 | Black and red travelers of the 3-wire cable | The two brass traveler screws (either way round) |
| Switch 1 | White from the source and white of the 3-wire cable | Spliced together with a wire connector, not on the switch |
| Switch 2 | Black and red travelers of the 3-wire cable | The two brass traveler screws (either way round) |
| Switch 2 | Black going to the light | Dark COM screw |
| Switch 2 | White of the 3-wire cable and white to the light | Spliced together with a wire connector |
| Both boxes | Bare copper or green grounds | Pigtail to the green ground screw on each switch (and the metal box, if metal) |
- The incoming black (hot) goes to the dark COM screw on Switch 1 and the two travelers go to the brass screws; either traveler can go to either brass screw.
- On Switch 2 the dark COM screw takes the black wire that goes up to the light. The neutrals (white) are spliced together in each box and never touch the switch.
- This is the pillar's "Diagram 1" layout, and it keeps a neutral in both switch boxes for future smart switches and dimmers.
Power at the light
| Box | Conductor | Connects to |
|---|---|---|
| Light box | Black and white from the source | Black to the fixture and to the amber feed; white (neutral) to the fixture neutral |
| Switch 1 | Black of the 2-wire cable from the light (switched leg) | Dark COM screw |
| Switch 1 | White (amber tape) of the 2-wire cable and of the 3-wire cable | Spliced together with a wire connector: the hot feed passes through, not on the switch |
| Switch 1 | Black and red travelers of the 3-wire cable | The two brass traveler screws (either way round) |
| Switch 2 | White (amber tape) of the 3-wire cable: hot feed | Dark COM screw |
| Switch 2 | Black and red travelers of the 3-wire cable | The two brass traveler screws (either way round) |
| All boxes | Bare copper or green grounds | Bonded together and to the green ground screw on each switch |
- The hot feed (white, re-identified with amber tape) leaves the light box, passes through the Switch 1 box on a wire-connector splice (it is not connected to Switch 1) and lands on the dark COM screw of Switch 2.
- The black wire from the Switch 1 COM screw is the switched leg back up to the light.
- No neutral reaches either switch box in this layout. That is common in older homes, but for new work the NEC (404.2(C), since the 2011 edition) generally requires a neutral at switch locations, so new runs usually use cable with an extra conductor; your inspector applies the edition your area adopted. Check before buying a smart switch or dimmer that needs one. A white wire that carries hot must be re-identified with a colour other than white, gray or green, so it cannot be mistaken for a neutral.
- This is the pillar's "Diagram 2" layout. The pillar's drawing shows the amber conductor to Switch 1; the continuation of the feed through the Switch 1 box to Switch 2 COM follows from the pillar's statement that Switch 2 COM is "Hot In" on a 3-wire cable (derived, see notes).
Adding a 4-way switch (3 locations)
| Box | Conductor | Connects to |
|---|---|---|
| Switch 1 (3-way) | Black hot from the breaker | Dark COM screw |
| Switch 1 (3-way) | The two travelers to the 4-way | The two brass traveler screws |
| 4-way switch | The two travelers from Switch 1 | The IN pair |
| 4-way switch | The two travelers to Switch 3 | The OUT pair |
| Switch 3 (3-way) | The two travelers from the 4-way | The two brass traveler screws |
| Switch 3 (3-way) | Black going to the light | Dark COM screw |
| All boxes | White neutrals and bare or green grounds | Neutrals spliced through; grounds bonded to the green screw on each device |
- The 4-way switch has four traveler terminals, two IN and two OUT, and no COM screw. Land the two travelers coming from Switch 1 on the IN pair and the two going to Switch 3 on the OUT pair. Many 4-way switches mark the pairs; follow the markings on your device.
- Flipping the 4-way either passes the travelers straight through or swaps them, which is why the light can be switched from any of the three places. More 4-way switches can be added in the middle the same way.
- The pillar describes the 4-way run in words, not as a drawing. Traveler colours on the 4-way legs follow the same black and red convention and are not fixed by code; identify conductors by testing.
How the switching works
Each 3-way switch connects its COM terminal to one of two traveler terminals. The hot enters at the COM of one switch and the light is fed from the COM of the other.
two 3-way switches: light is ON when entry position = exit position with one 4-way: each crossed 4-way swaps the travelers, so the light is ON when entry position ≠ exit position in general: ON when (entry = exit) is flipped once for every crossed 4-way switch
- entry
- the 3-way switch whose COM takes the hot feed
- exit
- the 3-way switch whose COM goes to the light
Example: both switches in position A, light on. Flip either one and the light goes off. Flip the other and it comes back on. With a 4-way set to crossed, the same positions give a light that is off.
What this diagram does not cover
- Boxes with different cable, conduit work, older conductors or a mix of circuits. If your box does not match, stop and call a licensed electrician.
- Dimmers and smart switches, which have their own wiring rules. Follow the maker's instructions; see the dimmer guide.
- Box fill, wire size and breaker size. Use the minimum-AWG calculator for the table values and ask your authority having jurisdiction about local rules.
- Code details such as neutral at the switch, stairway lighting and re-identifying white conductors are discussed in the full wiring guide, and the guide's 4-way section explains the third location.
Frequently asked questions
Which terminal is the common on a 3-way switch?
The COM (common) terminal is the one that stays attached to the hot feed on the first switch or to the wire that goes to the light on the second switch. On many screw-terminal switches it is a darker screw, and on lever switches it is marked as the Common lever. The two traveler terminals are interchangeable, but the COM terminal is not. Never rely on wire colour alone: label the wire on COM before you disconnect an old switch, and identify unknown wires by testing.
What do the traveler wires do?
The two travelers connect the two 3-way switches to each other. Each switch connects its COM terminal to one traveler or the other, so the light is on when both switches have chosen the same traveler and off when they have chosen different ones. Try it in the diagram: flip either switch and the energized wires change.
Is there a neutral at the switch?
It depends on the layout. With power at the first switch (shown first above) a neutral is present in both switch boxes. With power at the light, no neutral reaches either switch box, and the white wire that carries hot power must be re-identified with a colour other than white, gray or green. Check before you buy a smart switch or dimmer that needs a neutral. For new work, the NEC (404.2(C)) generally requires a neutral at switch locations; check the code edition your area enforces.
How does a 4-way switch fit in?
A 4-way switch goes in the middle of the traveler run when you want a third location. Its two IN terminals take the travelers from one 3-way switch and its two OUT terminals go to the other 3-way switch. It has no COM terminal. In one position it passes the travelers straight through and in the other it swaps them, so the light can be switched from any of the three places.
Can I wire this myself?
Many homeowners do replace a switch, but this diagram is a teaching schematic and not instructions for your house. Your box may have different cable, older conductors or a different arrangement. ESFI strongly recommends hiring a qualified, licensed electrician for electrical work, and your local authority decides whether a permit is needed. If the wiring in your box does not match what you see here, stop and call a licensed electrician.
Sources
- Leviton, Lever Edge 3-way switch installation instructions (E5603): common, traveler and ground terminals; travelers interchangeable; neutral not required; turn off power and test (leviton.com) Accessed 2026-11-14.
- ESFI, Do-It-Yourself (DIY) Electrical Safety: breaker off, test the wires, hire a licensed electrician (esfi.org) Accessed 2026-11-14.
- CPSC, Plug into Safety! (NSN 18-07): hire a licensed electrician for electrical work in the home (cpsc.gov) Accessed 2026-11-14.
- ESFI, Switch to Safety: warning signs at a switch and "all light switches should be installed by a professional" (esfi.org) Accessed 2026-11-14.