Many drivers have experienced the same frustrating moment during nighttime driving. The road ahead is dark and quiet when suddenly a vehicle pulls in behind them with blinding LED headlights flooding the rearview mirror.

The glare can become so intense that it briefly affects visibility and concentration. What surprises many people is that most vehicles already include a simple built-in solution hidden in plain sight. Beneath the rearview mirror is a small tab designed specifically to reduce headlight glare at night, yet countless drivers either overlook it completely or never learn what it actually does.

Flipping the tiny tab changes the angle of the mirror and activates what is commonly called “night mode.” Instead of reflecting bright light directly into the driver’s eyes, the mirror shifts to a dimmer reflection that softens the glare significantly. The difference may seem subtle at first, but once bright headlights appear behind the vehicle, the improvement becomes obvious. The system works using a wedge-shaped piece of glass that reflects light differently depending on the mirror’s position. Even though the technology is decades old, it remains effective without needing electronics, sensors, or batteries.

Modern headlights have made this feature more useful than ever. LED and HID lighting systems are far brighter than older halogen bulbs, and many SUVs and trucks sit high enough for their lights to shine directly into mirrors. On highways and dark roads, using the dimming feature can greatly improve comfort and visibility during long drives.

Newer vehicles often replace the manual tab with automatic dimming mirrors that darken on their own whenever bright light is detected. These systems use sensors and electrochromic glass to adjust automatically, then return to normal once the glare disappears. Whether manual or automatic, the feature exists for one reason: helping drivers see clearly and stay safer when harsh headlights suddenly appear behind them.