Navigation lights
What Lights Does a Sailing Boat Show at Night? Rule 25 Guide
Published · Last checked October 2026
A sailing boat under way at night shows red and green sidelights and a white sternlight (COLREGs Rule 25). A yacht under 20 metres may combine these into a single tricolour lantern at the masthead. A sailing vessel may also show an all-round red over green at the masthead, but not with a tricolour. Under 7 metres, a white torch ready to show is enough if fixed lights are impractical. Once the engine is running, show power-driven lights instead.
The basic set
Rule 25(a) requires a sailing vessel under way to show sidelights (red to port, green to starboard, each covering 112.5 degrees from ahead to 22.5 degrees abaft the beam) and a sternlight (white, covering 135 degrees astern). Together they make a full circle with no gaps or overlaps of significance.
Options for sailing vessels
| Option | Who may use it | Notes |
|---|---|---|
| Sidelights + sternlight | Any sailing vessel | Standard arrangement, often at deck level |
| Masthead tricolour | Under 20 m | Replaces sidelights and sternlight; sailing only |
| Red over green all-round at masthead | Any sailing vessel | Added to sidelights and sternlight, never with a tricolour |
| White torch or lantern | Under 7 m | Shown in time to prevent collision if fixed lights impractical |
| Same as under-7 m sailing | Vessel under oars | Rule 25(d)(ii) |
A tricolour is more visible over waves and uses one bulb, which is why many cruising yachts use it offshore. See the tricolour light guide for when not to use it.
Under engine or motor-sailing
With the engine propelling the boat, you are a power-driven vessel. Switch off any tricolour and show:
- A forward-facing white masthead (steaming) light, covering 225 degrees, usually halfway up the mast
- Deck-level red and green sidelights
- A white sternlight
A power vessel under 12 m may instead show one all-round white light plus sidelights. A common mistake is leaving the tricolour on with the steaming light: that tells others you are both sailing and motoring.
Ranges
| Light | Under 12 m | 12 to 20 m |
|---|---|---|
| Masthead light | 2 miles | 3 miles |
| Sidelights | 1 mile | 2 miles |
| Sternlight | 2 miles | 2 miles |
| All-round light | 2 miles | 2 miles |
Lights are shown from sunset to sunrise and in restricted visibility. Revise them in the night sailing lesson and the navigation lights guide.