That Extra Red Bulb That Comes With Your Christmas Lights Has a Special Purpose

Think about your current set of Christmas lights. Did it come with several red-tipped bulbs?

Depending on your experience with holiday decorating, you might have thought they were just spares. If so, you've also probably wondered why they have red tips.

As it turns out, they're actually blinker bulbs, also known as flasher bulbs. In other words, when you install the bulb into the string light, the lights after that bulb will blink. This lets you create a decorative effect that's equal parts fun and festive.

On TikTok, user @viznelly demonstrated the blinker bulb's function in their own lights. The caption reads, "I was today years old when I found out what these are for."

Many TikTokers were in the same boat, noting that they always thought the red-tipped bulbs were spares. However, other users were surprised that this wasn't common knowledge.

But how do blinker bulbs work, exactly? According to How Stuff Works, the special bulbs contain a piece of metal called a bi-metallic strip. When an electrical current runs into the bulb, the strip bends, which turns off the light. When the strip cools down, the strip bends back and the bulb relights.

If you still have your Christmas lights' instruction manual, be sure to check it out. It will likely list specific instructions and tips on using blinker bulbs. Otherwise, it's recommended to install the blinker bulb near the beginning of the string light so that everything after it flashes.

While we're on the topic of lights, try vertically stringing your Christmas tree in an S-formation. This will ensure the lights don't get buried in the branches. Not to mention, it will be a heck of lot easier to remove them after the holidays. The more you know!