A CRT monitor uses a beam of electrons to draw images on a glass screen

CRT stands for cathode ray tube. Inside the monitor is a large glass vacuum tube. At the back of that tube sits an electron gun — a device that fires a thin beam of electrons toward the front of the screen. That beam moves across the screen very quickly, left to right and top to bottom, lighting up phosphor dots on the inside surface of the glass. Your eye blends all those dots together into the image you see.

This technology powered almost every computer monitor and television made before the year 2000, and many continued in use well into the 2010s. If you are setting up a used computer or working with older equipment, you may run into a CRT monitor. They are heavy, take up a lot of desk space, and use more electricity than modern displays — but they have some characteristics that made them standard for decades.

Key Takeaways

  • CRT monitors work by firing an electron beam at phosphor dots on a glass screen, creating images one line at a time from top to bottom.
  • A CRT monitor requires a specific refresh rate — usually 60 Hz or higher — to avoid visible flicker that can cause eye strain.
  • CRT monitors produce radiation and require proper ventilation, so they should not be placed in enclosed spaces or near heat-sensitive equipment.
  • If you are connecting a CRT monitor to a modern computer, you will need a video adapter because most new graphics cards no longer have the analog video outputs CRTs require.

How the image gets drawn on the screen

The electron beam does not light up the entire screen at once. Instead, it starts at the top left corner and moves horizontally across the screen, creating one thin line of the image. When it reaches the right edge, it jumps back to the left and moves down one line. This happens over and over, from top to bottom, many times per second.

The speed at which the beam completes one full top-to-bottom cycle is called the refresh rate, measured in hertz (Hz). A monitor with a 60 Hz refresh rate redraws the entire image 60 times per second. A 75 Hz monitor does it 75 times per second. If the refresh rate is too low, your eye can see the beam drawing the image, which appears as a flicker. This flicker causes eye strain and headaches during long use. Most CRT monitors ran at 60 Hz or higher to keep flicker below the threshold of human perception.

Why CRT monitors were the standard for so long

CRT technology had real advantages that made it the only practical choice for decades. The image quality was sharp at any resolution the monitor could display, because the electron beam could be focused to a very fine point. Colors were accurate and consistent across the screen. The monitor could display different resolutions without any loss of clarity — you could run 640×480, 800×600, or 1024×768 on the same physical monitor just by changing the settings in your operating system.

CRT monitors were also relatively inexpensive to manufacture at scale, which is why they remained standard even after flat-panel technology was invented. A 17-inch CRT monitor cost less than a 15-inch LCD monitor through much of the 1990s. They worked with any graphics card that had a standard analog video output port, which was universal on computers of that era.

Physical size and weight

A CRT monitor is much deeper than a modern flat-panel display. A 17-inch CRT monitor — measured diagonally across the screen — might be 16 inches wide, 15 inches tall, and 18 inches deep from front to back. A modern 17-inch LCD monitor is typically 16 inches wide, 10 inches tall, and 2 inches deep. The CRT is also significantly heavier, often weighing 40 to 60 pounds, because the glass tube and the electromagnets that steer the electron beam are dense and substantial.

This depth and weight made CRT monitors impractical for laptop use and difficult to position on small desks. It also meant that moving a computer setup required real physical effort. The large footprint is the main reason CRT monitors disappeared from new computer sales once LCD technology became affordable, around 2005 to 2008.

Power use and heat output

A CRT monitor consumes more electricity than a comparably sized LCD monitor. A typical 17-inch CRT used 80 to 120 watts during normal operation. A modern 17-inch LCD uses 20 to 40 watts. Over the course of a year, that difference adds up in your electric bill. The CRT also generates significant heat, which is why older computer setups often had ventilation problems if equipment was packed too tightly together.

The electron gun inside a CRT monitor operates at very high voltage — typically 20,000 to 30,000 volts. This voltage is necessary to accelerate the electrons to the speed needed to light up the phosphor. Because of this high voltage, CRT monitors produce a small amount of electromagnetic radiation. Modern CRT monitors were shielded to reduce this radiation to safe levels, but it is one reason why CRT monitors should not be placed in enclosed spaces or very close to other sensitive electronics.

Connecting a CRT monitor to a modern computer

Most CRT monitors use a 15-pin analog video connector called a D-sub or VGA port. This is a trapezoid-shaped port with three rows of small pins. Modern graphics cards — especially those built into newer processors — no longer include this analog output. If you want to use a CRT monitor with a current computer, you will need a video adapter that converts from HDMI, DisplayPort, or USB-C to analog VGA.

These adapters are inexpensive and widely available online, but they are not always reliable. Some adapters work well; others introduce image quality problems like ghosting or color shifts. Before investing in an adapter, test it if possible, or buy from a seller with a return policy. You should also verify that your graphics card's driver supports the resolution and refresh rate you want to use, because some modern drivers have limited support for analog video output.

When you might still encounter a CRT monitor

CRT monitors are rare in new setups but still appear in specific situations. Older industrial equipment, medical devices, and arcade machines often use CRT displays because the technology is reliable and the equipment was built around it. Some people who work with retro computers or gaming consoles prefer CRT monitors because the image quality and color reproduction match what the original hardware was designed for. Vintage computer enthusiasts sometimes seek out CRT monitors specifically for this reason.

If you inherit a computer setup that includes a CRT monitor and you want to continue using it, the main obstacles are finding the right video adapter and having enough desk space. The monitor itself will likely work fine if it has not been damaged — CRT monitors are durable and often outlast the computers they were paired with.

Frequently Asked Questions

Is it safe to use a CRT monitor?

Yes, modern CRT monitors that meet safety standards are safe for normal use. The radiation they produce is minimal and shielded. The main precautions are to avoid placing the monitor in a very hot or enclosed space, to keep it away from magnets, and to allow proper ventilation around it. Do not open the monitor yourself — the high voltage inside can cause serious injury.

Why does my CRT monitor flicker?

Flicker usually means the refresh rate is set too low. Try increasing it to 75 Hz or higher in your display settings. If the monitor does not support a higher refresh rate, or if flicker persists after increasing the refresh rate, the monitor may be aging and losing the ability to hold a stable image. Persistent flicker that does not improve with refresh rate changes usually means the monitor is nearing the end of its usable life.

Can I use a CRT monitor with a laptop?

Most laptops have HDMI or USB-C output, not VGA. You would need an adapter to connect a CRT monitor to a laptop. However, because laptops have smaller graphics processors and CRT monitors require more power to drive, the combination is not practical for regular use. It is better suited to occasional use or testing.

What should I do with an old CRT monitor I no longer need?

CRT monitors contain glass and electronic components that should not go in regular trash. Many electronics recycling programs accept CRT monitors for free or a small fee. Contact your local waste management authority or search for "electronics recycling near me" to find a facility that takes them. Some computer repair shops also accept old monitors for recycling.

Why is the image blurry or distorted on my CRT monitor?

CRT monitors have adjustment knobs or on-screen menus to fine-tune the image. Look for controls labeled "focus," "brightness," "contrast," or "geometry." Adjusting these can often improve image clarity. If the image is still blurry after adjustment, the monitor may need internal repair or replacement. Distortion can also be caused by nearby magnets or metal objects — try moving those away from the monitor.