Two clocks that rarely agree
A display refreshes on a fixed schedule. At 60 times per second, it starts a new pass over the screen about every 16.7 milliseconds, drawing the image from top to bottom. A computer or game console, meanwhile, produces frames whenever it finishes them. A simple scene might be ready in a few milliseconds, a busy one in far longer, and the time varies from frame to frame.
So there are two independent clocks: one belonging to the display, one belonging to the source. Unless something forces them to cooperate, they drift in and out of step.
What tearing looks like
Screen tearing appears when the source swaps in a new frame while the display is partway through drawing the previous one. The top part of the screen shows the old frame and the lower part shows the new one, with a visible seam between them. If the camera or scene is moving sideways, objects look sliced, with the upper and lower pieces slightly offset.
Tearing is most noticeable in fast horizontal motion, such as panning across a scene, and it can appear in games, in some video playback and on desktops with certain settings. It does not mean the panel is faulty. It is a timing mismatch, and it can happen on any display that refreshes at a fixed rate.
The traditional fix: vsync
Vertical synchronization, usually called vsync, tells the source to wait and only swap frames during the short gap between the display’s refresh passes. That removes the seam, since each pass shows exactly one complete frame.
The cost is timing. If a frame misses its slot, the display shows the previous frame again for another full refresh. On a 60 Hz display, a frame that takes slightly longer than 16.7 milliseconds ends up waiting for the next slot, so the screen effectively updates less often. That produces uneven motion, often called stutter, and can add delay between an action and its appearance on screen. Some systems queue several frames to smooth things out, which can add more delay again.
Without vsync, you get the lowest delay but possible tearing. With vsync, you usually avoid tearing but may see stutter and extra delay. Neither is ideal.
Variable refresh: let the display follow the source
Adaptive sync, sold under various brand names, reverses the relationship. Instead of the source waiting for the display, the display waits for the source. Within a supported range, it begins a refresh when a new frame is ready, so the interval between refreshes follows the frame delivery.
If frames arrive every 12 milliseconds, then every 20, then every 15, the display refreshes at those moments rather than on a rigid schedule. A frame is never swapped in mid-pass, so there is no seam, and a late frame does not have to wait for the next fixed slot.
This only works when several things line up:
- the display must support variable refresh over the connection in use
- the graphics hardware and its drivers must support it
- the frame rate must stay inside the display’s supported range
- the feature must be switched on, which is sometimes a setting in both the monitor menu and the computer
The supported range is worth checking in the manufacturer’s specification, since it differs between displays. Below the bottom of the range, some systems repeat frames to stay in range, and results vary by implementation. Above the top of the range, the display can no longer follow, and tearing or vsync behavior returns depending on your settings.
What adaptive sync does not do
It is easy to expect more from the feature than it delivers.
- It does not raise the frame rate. If the source produces few frames, the picture is still choppy, only without tearing.
- It does not remove all delay. It addresses the waiting caused by fixed schedules, but other sources of lag are separate, which is the topic of input lag.
- It does not change how fast pixels transition. Motion blur and smearing come from the panel’s response time and from how motion is displayed, and are unaffected.
- It may interact with brightness behavior. On some panels, changing refresh rates quickly can cause slight brightness or flicker differences, particularly in dark scenes. Whether you notice depends on the panel type and implementation.
Related practical points
Adaptive sync generally works over specific connections and not others, so the cable and port you choose can decide whether the option appears in settings. If it is missing, check the connector, the display’s menu and the computer’s graphics settings before assuming it is unsupported.
On televisions and consoles, a similar idea exists under different labels, and a game mode setting may be required to enable it. It is mostly relevant to gaming monitors and console gaming displays, although smooth video playback at unusual frame rates, such as film content on a fixed refresh display, is a related timing problem that variable refresh can sometimes help with.
If tearing is not bothering you, there is no need to change anything. For many everyday uses, a fixed refresh rate with vsync, or a display with a high refresh rate that makes tearing less visible, is perfectly adequate. Because the right choice depends on what you play or watch, how steady your frame rate is and how sensitive you are to delay or tearing, it is reasonable to try the options and keep whichever looks best to you.