A page sees the signal the computer sends, not the panel. The patterns below show the rest.
Upright red and blue lines, with a black and white control
Upright red and blue lines, with a black and white control
Preview · enlarged so the lines show
Red and blue columns one pixel wide fill the top two thirds, and the same columns in black and white fill the rest. Put your eyes close and compare the two parts: is the color as crisp as the control, or smeared into one shade?
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Click, tap or press the right arrow for the next one. The left arrow goes back.
Upright red and blue lines, with a black and white controlRed and blue columns one pixel wide fill the top two thirds, and the same columns in black and white fill the rest. Put your eyes close and compare the two parts: is the color as crisp as the control, or smeared into one shade?
Level red and blue lines, with a black and white controlThe same lines turned on their side, each row one pixel high. Color resolution can be cut across the screen and kept down it, so a signal can pass one of these two patterns and fail the other.
Both directions at once, red on blueFour blocks of one-pixel lines: upright on the left, level on the right, red lines on blue above and blue lines on red below. Compare left with right. This one picture separates 4:4:4, 4:2:2 and 4:2:0.
Both directions at once, magenta on greenMagenta and green are opposites: averaged, they make gray. Where color is subsampled these lines lose their color or take a single tint, a plainer change than red and blue blurring toward purple.
Both directions at once, blue on blackBlue gives only about 7 percent of a picture's brightness, so these lines are almost all color and very little light. On a subsampled signal the black lines fill with blue and each block turns nearly flat.
Show all 16 patterns and checks (11 more)
What you see and which format it means 5
Color lines as crisp as the black and whiteFull color resolution. In 4:4:4 all three parts of the signal have the same sample rate, and RGB has no subsampling either, so each pixel keeps its own color. This is the format for a screen used with a computer.
Upright lines smear, level lines stay crisp4:2:2. Color is sampled at half the rate of brightness across the screen and at the full rate down it, so two neighbors in a row share one color. The signal needs two thirds of the bandwidth of 4:4:4.
Lines smear in both directions4:2:0. Color is halved across the screen and down it, so each block of four pixels shares one color, and the signal needs half the bandwidth of 4:4:4. Of the three formats it keeps the least color detail.
The black and white control is soft tooThen color is not the cause. Subsampling leaves brightness at full resolution, so black and white lines stay crisp under it. A soft control means the whole picture is being resized: by page zoom, by display scaling, or by the screen.
Every block looks purple from your seatExpected, even at 4:4:4. The eye resolves color at about a third of the detail it resolves in brightness, which is why subsampling exists at all. Judge from close up, or through a phone camera held near the screen.
If the color lines smear 6
Zoom at 100 percent before anything elsePage zoom changes how many screen pixels one CSS pixel covers, so a zoomed page cannot always land a one-pixel line on one pixel. Reset zoom and read the pixel ratio in the numbers above the picture before you judge any block.
Ask the computer for RGB or 4:4:4The format is chosen by the source. In the computer's display settings or the graphics card's software, find the color format and pick RGB or YCbCr 4:4:4. Then look at the red and blue lines again.
Label the TV's input as a PCA TV has to be told to expect an unsubsampled signal. On most TVs that means changing the label of the HDMI input in use to PC, and the steps differ by maker. Do it for each input you connect a computer to.
A port and cable that carry the full signalHDMI 2.0 carries 18 gigabits a second, enough for 4K at 60 Hz in 8-bit RGB and no more. Add 10-bit color for HDR, or 120 Hz, and the link needs HDMI 2.1, which carries up to 48, or a subsampled format.
Trade refresh rate for colorHalving the refresh rate halves the data, and so does 4:2:0. If 4K at 60 Hz arrives subsampled, set 30 Hz and look again. Where the color lines then turn crisp, the link was the limit, not the screen.
TV sharpness to neutralA TV's Sharpness control is edge enhancement: it adds a bright and a dark fringe beside every edge, and one-pixel lines are nothing but edges. Fringes can pass for smeared color, so set it to neutral before you judge.
How this list was compiled: The patterns are this site's own, drawn by the page as one-pixel lines, and no maker's chart is copied. Computed: a signal's bandwidth relative to 4:4:4 is its three figures summed and divided by 12 (two thirds for 4:2:2, half for 4:2:0), magenta and green average to a neutral gray, and blue gives about 7 percent of white's light by the luminance weights at https://en.wikipedia.org/wiki/SRGB. That chroma subsampling gives color less resolution than brightness, that human vision processes color at roughly one third of luminance's resolution, that in 4:4:4 the three components have the same sample rate and RGB has no chroma subsampling either, that 4:2:2 halves the horizontal chroma resolution, that 4:2:0 subsamples color by a factor of 2 each way, across and down and is the scheme of DVD, Blu-ray and most MPEG video, that magenta and green are the article's example of complementary colors at a border, and that with alternating one-pixel lines color is reconstructed onto the neighboring pixels, is from https://en.wikipedia.org/wiki/Chroma_subsampling. That HDMI 2.0 has a bandwidth of 18 Gbit/s and carries 4K at 60 Hz with 24 bits a pixel, that formats needing more than that, such as 4K at 60 Hz with 10 bits a channel for HDR or 4K at 120 Hz, may need the cables of HDMI 2.1, whose bandwidth is 48 Gbit/s, is from https://en.wikipedia.org/wiki/HDMI. That a computer's color format is set to RGB or YCbCr 4:4:4 in its display settings or the graphics card's software, that most TVs must have the HDMI input in use labeled PC before they show an unsubsampled signal, and that subsampling makes text on a desktop look fuzzy, is from https://www.rtings.com/tv/learn/chroma-subsampling. That page zoom changes the ratio of screen pixels to CSS pixels is from https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio. That a television's sharpness control is edge enhancement, which adds a bright and a dark highlight on either side of an edge, is from https://en.wikipedia.org/wiki/Edge_enhancement. All read 2026-10-06. A web page cannot see which format the screen receives: every reading here is made by eye. Licence: own work
How it works
This 4:4:4 test pattern draws red and blue lines one pixel wide above the same lines in black and white. Color as crisp as the control means full color is arriving. If not, the third pattern tells 4:2:2 from 4:2:0.
Read the full guide
The 4:4:4 monitor test, step by step
1. Reset page zoom to 100 percent, press Go full screen and put your eyes close to the screen.
2. Color lines as crisp as the black and white ones: 4:4:4 or RGB. You are done.
3. Color smeared and the control crisp? Click, tap or press the right arrow twice for both directions at once.
4. Only the upright lines smear: 4:2:2. Upright and level both smear: 4:2:0.
Questions and answers
Is RGB the same as 4:4:4?
For this test, yes. 4:4:4 names a Y'CbCr signal with no chroma subsampling, and RGB is another encoding that has none either. Both give every pixel its own color, and the pattern looks the same under each.
Does 4:2:0 matter for films and games?
Hardly for films: discs and most compressed video are stored in 4:2:0 already, so nothing more is lost. Most games lose little too. It matters on a desktop, where thin colored text and one-pixel lines are exactly the detail that subsampling throws away.
Can a web page tell which chroma format my screen receives?
No. A page sees only what the browser draws. The format is settled between the graphics card and the screen, after the page's work is done, which is why this is a pattern you read by eye.