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Can you use indoor Christmas lights outside?

Only if the lights are marked for it. Use a set outside only when its tag or box says it’s for outdoor use, or for indoor and outdoor use.

What does the set’s tag or box say?

For outdoor use, or indoor and outdoorOr it has a red UL holographic labelFor indoor use onlyOr it has a green UL holographic labelI can’t find a markingNo words or label about where it can go

What to do

Use it outside, on a GFCI

A set marked for outdoor use can go outside.

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Outdoor extension cords Portable GFCI plugs
  • If there’s no GFCI outlet outside, use a portable GFCI, or have a qualified electrician install one.
  • Any extension cord you use outside must be marked for outdoor use.

See also

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What to do

Keep it indoors

A set marked for indoor use only isn’t for outside.

Available on Amazon

Indoor and outdoor Christmas lights
  • For outside, use a set marked for outdoor use.

See also

How many light stringsChristmas light fusesC7 vs C9 vs mini bulbs
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What to do

Don’t use an unmarked set outside

Lights not marked for outdoor use aren’t for outside.

Available on Amazon

Indoor and outdoor Christmas lights
  • Check the tag near the plug, the box and the instruction sheet.
  • If none of them says outdoor use, don’t use it outside. Indoors or out, use only lights tested by a lab such as UL or ETL.

See also

How many light stringsChristmas light fusesC7 vs C9 vs mini bulbs
Start over

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Unplug the lights before you hang them, take them down or change a bulb.

Plug outdoor lights into a GFCI-protected outlet or a portable GFCI, and use an extension cord marked for outdoor use.

Reading the label

UL marks light strings for indoor use only with a green holographic label, and strings for indoor or outdoor use with a red one. On lights tested by another lab, such as ETL, go by the words on the tag.

Some lights are made for indoors or outdoors, but not both. Holiday Living’s clear C9 set, for example, is marked only “For outdoor use.”

Extension cords outside

Extension cord warning tags (UL 817 calls for one) carry the line “Do not plug one extension cord into another.” For how many light sets can be connected end to end, see how many light strings you can connect.

Hanging them

Use clips, not nails, so the cords don’t get damaged.

Switch the lights off at bedtime and whenever you leave the house.

Common questions

Can I leave outdoor Christmas lights up all year?

GE's mini light set instructions say the set is not intended for permanent installation or use, and the NFPA's advice is to bring outdoor lights inside after the holidays.

Can I run the cord through a door or window?

No. Don't run extension cords through doorways, and closing a door or window on lights or cords can damage the wire insulation.

Keep going

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Where we get our information from

The outdoor and GFCI rules come from the light makers’ own instruction sheets and the CPSC, the label colors from UL, the extension cord rules from the CPSC and an OSHA letter on UL 817, and the hanging advice from the NFPA. Checked against published data from NFPA, CPSC, GE, Holiday Living and UL Solutions (plus 1 more).

See all 8 sources
  • GE mini light set instructions, models 61515LO and 61516LO (Nicolas Holiday, 2025): set watts, end-to-end maximum, amps times 120, fuses, GFCI outlet outdoors
  • Holiday Living light set instructions: clear C9 set W11C0154 (432 W maximum) and 6.5 ft. pre-lit Seneca Pine tree W14L0441 (lights rated 24 W, 216 W maximum)
  • National Fire Protection Association, Winter Holiday Safety tip sheet (2025): number of light strands to connect, lights off at bedtime
  • US Consumer Product Safety Commission, “Do’s and Don’ts of Holiday Decorating” (2009): tested lights, damaged sets, lights off at bedtime
  • UL Solutions, “BULLETIN: Decorative Lighting Strings”: green and red holographic labels
  • US Consumer Product Safety Commission, “Household Extension Cords Can Cause Fires” (Pub 5032): the rating on the tag, hot cords, at least 16 AWG, temporary use, cords marked for outdoor use, not through doorways
  • OSHA interpretation letter, September 28, 2015: the UL 817 extension cord warning tag
  • National Fire Protection Association, Christmas Tree Safety tip sheet (2025): bring outdoor lights inside after the holidays

General guidance from manufacturer and standards data. Products vary, so check the label and the maker's instructions.