Light color
What Does a Red Light Mean?
Red lights often indicate alerts, errors, warnings, low battery, overheating, blocked sensors, or urgent status states depending on the device.
Guides with red lights
Router Solid Red Light
A solid red light on a router usually means the router has no internet connection, failed to connect to the modem, detected a service issue, or is showing a device-specific fault.
Router & Modem Lights · General
Smoke Alarm Blinking Red Light
A blinking red light on a smoke alarm can mean normal operation, a recent alarm event, low battery, hush mode, or a device-specific warning depending on the model.
Smoke Alarm Lights · General
Carbon Monoxide Detector Red Light
A red light on a carbon monoxide detector can indicate alarm, fault, memory, low battery, or end-of-life depending on the model. Treat any CO alarm as serious.
Carbon Monoxide Detector Lights · General
Eero Red Light
A red light on an eero usually means the device is not connected to the internet or cannot reach the network correctly.
Router & Modem Lights · eero
Epson Printer Red Light Blinking
A blinking red light on an Epson printer usually means the printer needs attention, commonly from paper, ink, jam, cover, maintenance, or a model-specific fault.
Printer Lights · Epson
First Alert Blinking Red Light
A blinking red light on a First Alert alarm can mean normal operation, alarm memory, an active alarm, low battery, or another model-specific condition.
Smoke Alarm Lights · First Alert
Kidde Smoke Alarm Red Light
A red light on a Kidde smoke alarm can indicate normal status, alarm memory, active alarm, low battery, hush mode, or a model-specific warning.
Smoke Alarm Lights · Kidde
CO Detector End-of-Life Light
A CO detector end-of-life light means the alarm has reached the end of its sensor life and should be replaced, not ignored.
Carbon Monoxide Detector Lights · General
DeWalt Charger Flashing Red Light
A flashing red light on a DeWalt charger commonly means the battery is charging, but different flash patterns can also indicate hot/cold delay or a battery problem.
Power Tool Lights · DeWalt
Milwaukee Charger Red and Green Flashing
Red and green flashing lights on a Milwaukee charger usually indicate a battery or charger status code that needs to be checked against the charger manual.
Power Tool Lights · Milwaukee
Ryobi Charger Flashing Red Light
A flashing red light on a Ryobi charger can mean charging, temperature delay, or a fault depending on the charger model and flash pattern.
Power Tool Lights · Ryobi
Power Bank Blinking Light
A blinking light on a power bank usually means it is charging, discharging, low on battery, checking capacity, or reporting a fault depending on color and pattern.
Battery Charger Lights · General
Blink Camera Red Light
A red light on a Blink camera usually points to setup, connection, low battery, recording, or camera status depending on the model and pattern.
Security Camera Lights · Blink
Blink Sync Module Red Light
A red light on a Blink Sync Module usually means it is not connected correctly, has a Wi-Fi problem, or is in a setup or error state.
Smart Home Lights · Blink Sync Module
Samsung TV Red Light Blinking
A blinking red light on a Samsung TV usually means standby, remote signal, startup, power supply, or a failure to turn on depending on the model.
TV & Streaming Device Lights · Samsung
Battery Light on Dashboard
A battery light on the dashboard usually means the vehicle charging system is not working correctly, not simply that the battery is old.
Car Dashboard Lights · General
Oil Pressure Light
An oil pressure light can mean the engine does not have enough oil pressure. It should be treated as serious because continuing to drive can destroy the engine.
Car Dashboard Lights · General
Router Internet Light Red
A red internet light on a router usually means the router cannot reach the internet through the modem, gateway, ONT, or ISP connection.
Router & Modem Lights · General
Roku Red Light Flashing Low Power
A flashing red light on a Roku device often means the device is not getting enough power, especially if it is powered by a TV USB port.
TV & Streaming Device Lights · Roku
Sony TV LED Light Blinking
A blinking LED on a Sony TV can indicate remote activity, software update activity, timer status, startup behavior, or a TV problem depending on color and pattern.
TV & Streaming Device Lights · Sony
LG TV Red Light Blinking
A blinking red light on an LG TV usually points to standby, remote signal, startup, power behavior, or a failure to turn on depending on the model.
TV & Streaming Device Lights · LG
Nest Thermostat Blinking Red Light
A blinking red light on a Nest thermostat usually means the battery is very low and the thermostat is charging or needs power attention.
Smart Home Lights · Google Nest
Airbag Light on Dashboard
An airbag light usually means the supplemental restraint system detected a fault and the airbags or seatbelt pretensioners may not work correctly in a crash.
Car Dashboard Lights · General
Temperature Warning Light
A red temperature warning light usually means the engine is overheating or coolant temperature is too high. Continuing to drive can cause severe engine damage.
Car Dashboard Lights · General
Verizon Router Red Light
A red light on a Verizon router usually means the router has a connection problem, internet service issue, or router status warning depending on the model.
Router & Modem Lights · Verizon
AT&T Gateway Red Broadband Light
A red broadband light on an AT&T gateway usually means the gateway cannot establish or maintain its broadband connection.
Router & Modem Lights · AT&T
Thermostat Red Light
A red light on a thermostat can mean heating is active, emergency heat is on, battery is low, power is missing, or a model-specific fault is present.
Smart Home Lights · General
Ring Doorbell Red Light
A red light on a Ring doorbell may be related to infrared night vision, power, setup, or model-specific camera behavior depending on when it appears.
Security Camera Lights · Ring
Surge Protector Red Light
A red light on a surge protector can mean protected, grounded, fault, or warning depending on the label next to the light and the model.
Battery Charger Lights · General
Brake Warning Light
A red brake warning light can mean the parking brake is on, brake fluid is low, or the brake system has a fault that needs immediate attention.
Car Dashboard Lights · General
CPAP Red Light
A red light on a CPAP machine usually means the device needs attention, such as power, humidifier, filter, mask leak, service, or a model-specific fault.
Medical Device Lights · General
Color is only the first clue
A red light can mean different things on different devices. The device type, brand, model, and blink pattern matter just as much as the color.
How to read a red light
A red light is only the first clue. The device type, brand, model, light label, and blink pattern matter just as much as the color. For example, a red light on a charger, router, smoke alarm, printer, or dashboard can point to completely different conditions.
Use this page to narrow your search, then open the closest device-specific guide. If the light is connected to smoke, carbon monoxide, gas, electrical heat, battery swelling, medical equipment, or vehicle safety, treat it as a safety issue and follow official guidance first.
What to check first
- Find the device brand and model number.
- Check whether the light is solid, blinking, flashing, pulsing, or alternating.
- Look for nearby labels such as battery, alarm, internet, online, charging, fault, or service.
- Check whether the device is making a sound, displaying a message, or showing another warning.
- Do not assume the same color means the same thing across different devices.