A page sees the signal the computer sends, not the panel. The patterns below show the rest.
Checkerboard, 21 by 9
Checkerboard, 21 by 9
Preview · scaled to fit
Twenty-one squares across and nine down. On a screen of exactly 21:9 every cell would be square. In full screen on 2560 by 1080 each cell is about 122 pixels wide and 120 tall, and on 3440 by 1440 about 164 by 160: a touch wider than tall.
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Click, tap or press the right arrow for the next one. The left arrow goes back.
Checkerboard, 12 by 5Twelve squares across and five down. In full screen on 3840 by 1600, the one common size that is exactly 12:5, every cell is a square of 320 pixels. On 3440 by 1440 each is about 287 wide and 288 tall, too close to tell by eye.
Checkerboard, 21 by 9Twenty-one squares across and nine down. On a screen of exactly 21:9 every cell would be square. In full screen on 2560 by 1080 each cell is about 122 pixels wide and 120 tall, and on 3440 by 1440 about 164 by 160: a touch wider than tall.
Checkerboard, 32 by 9Thirty-two squares across and nine down, for the widest screens. In full screen on 5120 by 1440 every cell is a square of 160 pixels, on 3840 by 1080 one of 120 and on 7680 by 2160 one of 240. On a 21:9 screen the cells are taller than wide.
Show all 25 patterns and readings (22 more)
Ultra wide screen test patterns, continued
Frame 12.5 percent in: a 16:9 picture on 2560 by 1080A line on the screen edge and one frame 12.5 percent in. On 2560 by 1080 or 5120 by 2160 the frame's left and right lines stand where a full-height 16:9 picture ends: 320 or 640 pixels in. Its top and bottom lines mean nothing here.
Frame 12.8 percent in: a 16:9 picture on 3440 by 1440The same frame for the 43:18 shape. On 3440 by 1440 its left and right lines stand 440 pixels in, where a 2560 by 1440 picture ends and the black bars begin. The space outside those two lines is what a 16:9 video leaves empty.
Rulers with a number every 500 pixelsRulers along the top and left edges count real pixels, with a small mark every 50 and a long one every 500, numbered where it fits. On 3440 wide the long marks end at 3,000 with 440 pixels beyond; on 5120 wide the last is 5,000 with 120 beyond.
Readings for 21:9 and 32:9 screens 13
2560 by 1080 scaled to 125 percent: 2048 by 864With display scaling at 125 percent the browser is told 2048 by 864 and a pixel ratio of 1.25. Multiply them and 2560 by 1080 comes back, which is what Real pixels shows. The shape is still 64:27.
2560 by 1080: the 64:27 shape sold as 21:9The smallest common ultrawide: 2,764,800 pixels in a 64:27 shape, about 2.37 to 1. It is 1920 by 1080 with 320 more columns on each side, so a full-screen 16:9 video sits between two black bars 320 pixels wide.
3440 by 1440 scaled to 125 percent: 2752 by 1152At 125 percent the browser is told 2752 by 1152 with a pixel ratio of 1.25, and both figures are whole. At 150 percent the width would be 2293 and a third, so the reported size is rounded and Real pixels can be a pixel out.
3440 by 1440 with no scaling: bars of 4404,953,600 pixels in a 43:18 shape. It is 2560 by 1440 with 440 more columns on each side: a 16:9 video played full screen keeps its 2560 columns and leaves 880 dark, half on the left and half on the right.
3840 by 1080: two 1920 by 1080 screens4,147,200 pixels and exactly 32:9: two 1920 by 1080 screens side by side. It has the width of a 4K screen and half its rows. A full-screen 16:9 video fills the middle 1920 columns, with bars of 960 pixels.
3840 by 1600 scaled to 125 percent: 3072 by 1280At 125 percent the browser is told 3072 by 1280 with a pixel ratio of 1.25. At 150 percent it is told about 2560 by 1067, because 1600 divided by 1.5 is not whole. The pixel ratio is what separates this from a 2560-wide screen.
3840 by 1600: exactly 12:56,144,000 pixels and exactly 12:5, or 2.4 to 1: the widest of the three shapes sold as 21:9. It has the 3840 columns of a 4K screen and 1600 rows, not 2160. A 16:9 picture here is about 2844 wide, with bars of about 498 pixels.
5120 by 1440 scaled to 125 percent: 4096 by 1152At 125 percent the browser is told 4096 by 1152 with a pixel ratio of 1.25. The reported width looks like a cinema 4K figure, but the height gives it away: 4096 by 1152 is still 32:9.
5120 by 1440: two 2560 by 1440 screens7,372,800 pixels and exactly 32:9: two 2560 by 1440 screens side by side with no join. A full-screen 16:9 video fills the middle half, 2560 columns, and leaves a bar 1,280 pixels wide on each side.
5120 by 2160 scaled to 200 percent: 2560 by 1080At 200 percent this screen reports 2560 by 1080, the same size a 2560 by 1080 screen reports with no scaling. The pixel ratio tells them apart: 2 here, 1 there. Real pixels shows 5120 by 2160.
5120 by 2160: four times 2560 by 108011,059,200 pixels in the 64:27 shape, exactly four times 2560 by 1080. It is a 3840 by 2160 picture with 640 more columns on each side, so a 4K video shown full screen leaves bars 640 pixels wide.
7680 by 2160 scaled to 150 percent: 5120 by 1440At 150 percent this screen reports 5120 by 1440 with a pixel ratio of 1.5. A 5120 by 1440 screen reports the same size with a ratio of 1. Read the ratio before deciding which of the two you are looking at.
7680 by 2160: two 4K screens16,588,800 pixels and exactly 32:9: two 3840 by 2160 screens side by side, twice the pixels of one 4K screen. A full-screen 16:9 video fills the middle 3840 columns and leaves a bar 1,920 pixels wide on each side.
What the shapes mean 6
32:9 is two 16:9 screens joined32:9 is 16:9 doubled in width, and unlike 21:9 the figure is exact. 3840 by 1080 is two 1920 by 1080 screens, 5120 by 1440 two 2560 by 1440 and 7680 by 2160 two 4K screens. Half the width is always a standard 16:9 size.
A 16:9 reading on an ultrawide panelIf Real pixels reads 2560 by 1440 or 1920 by 1080 on an ultrawide monitor, the computer is sending a 16:9 picture. The monitor then either stretches it across the panel or shows it with bars. Stretched, the cells of every checkerboard here look wider.
A curved panel reads the same as a flat oneA browser is told pixels and a pixel ratio and nothing about the glass, so a curved monitor and a flat one of the same size report the same numbers. The patterns are drawn the same on both. The page cannot see the bend.
A full-screen video stays 16:9Most video is 16:9, so on a wider screen it keeps its shape and leaves a black bar on each side. The bar is half of the width minus the height times 16 over 9: 320 pixels on 2560 by 1080, 440 on 3440 by 1440.
A sales name that covers three shapes21:9 is a sales name. Exactly 21:9 would be 7:3, about 2.33 to 1, and no common monitor is. 2560 by 1080 and 5120 by 2160 are 64:27, 3440 by 1440 is 43:18 and 3840 by 1600 is 12:5, each a little wider than the label.
Color, banding and dead pixels on a wide panelThis page reads size and shape. The plain color fields, gray ramps and color bars on the other screen pages fill whatever panel they are shown on, so they cover the full width of a 21:9 or 32:9 screen with no setting to change.
How this list was compiled: Written for this page. Every exact ratio, pixel count, scaled size, cell size and bar width was computed: an aspect ratio is width and height divided by their largest common factor, the size a browser reports is the real size divided by the pixel ratio, and the bar a 16:9 picture leaves is half of the width minus the height times 16 over 9. That 21:9 is a consumer electronics marketing term for 64:27, that on computer monitors it also covers 43:18 and 12:5, and the sizes 2560 by 1080, 3440 by 1440, 3840 by 1600 and 5120 by 2160, are from https://en.wikipedia.org/wiki/21:9_aspect_ratio. That 32:9 is 16:9 doubled in width, and the sizes 3840 by 1080, 5120 by 1440 and 7680 by 2160, are from https://en.wikipedia.org/wiki/Ultrawide_formats. That the pixel ratio is the ratio of physical pixels to CSS pixels, and that page zoom changes it, is from https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio. All read 2026-10-02. A web page sees what the computer sends, never the panel itself. Licence: own work
How it works
This ultrawide monitor test reads the size and pixel ratio your browser is given and shows the real pixel count. Then go full screen: a checkerboard of 21 by 9 squares shows how close your screen is to that label.
Read the full guide
An ultrawide screen test in three steps
1. Read Real pixels. 2560 by 1080 is 64:27, 3440 by 1440 is 43:18 and 3840 by 1600 is 12:5.
2. Press Go full screen on the 21 by 9 checkerboard.
3. Cells a touch wider than tall are normal in a 21:9 monitor test: the label rounds all three shapes.
32:9 monitor test
For a super ultra wide monitor test pick the 32 by 9 checkerboard. On 5120 by 1440 or 3840 by 1080 every cell is an exact square, because 32:9 is two 16:9 screens side by side.
Set browser zoom to 100 percent first: zoom changes the pixel ratio.
Questions and answers
What should a 3440x1440 monitor test show?
Real pixels of 3440 by 1440. At 125 percent the browser reports 2752 by 1152 with a pixel ratio of 1.25, which multiplies back. Other scalings can read a pixel out. A full-screen 16:9 video leaves a black bar 440 pixels wide on each side.
Is an ultrawide curved monitor test any different?
No. A curved panel reports the same numbers as a flat one of the same size, and no browser is told about the bend. The patterns are drawn the same on both.
Which ultra wide screen test pattern shows the black bars?
The two frames. One stands 12.5 percent in, where a 16:9 picture ends on 2560 by 1080. The other stands 12.8 percent in, the same place on 3440 by 1440. Only their left and right lines count.
What else goes into an ultrawide gaming monitor test?
Refresh rate and motion, which have their own pages. The refresh rate test counts the frames your browser draws, and the ghosting test shows the trail behind a moving block.