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YUV is a color encoding system used as a part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently masked by the human perception than using a "direct" RGB-representation. The name YUV itself is derived from the Y'UV notation originally used for the luma (Y') and two chrominance (UV) components. The Y'UV model defines a color space in terms of one luma component (Y') and two chrominance components, called U (blue projection) and V (red projection), while YCbCr is a digital version of the Y'UV color model.

YUV signals are created from an original RGB (red, green and blue) source. The weighted values of R, G and B are added together to produce a single Y signal, representing the overall brightness, or luma, of that pixel. The U signal is then created by subtracting the Y from the blue signal of the original RGB, and then scaling; and V by subtracting the Y from the red, and then scaling by a different factor. These factors are chosen to make sure the range of each color space coordinate is roughly -0.5 to +0.5.

The transformation RGB→YUV is specified as follows: Y = 0.299R + 0.587G + 0.114B, U = −0.147R − 0.289G + 0.436B, V = 0.615R − 0.515G − 0.100B. Digital formats commonly use 8 bits for each channel, making the range for each 0 to 255, and so the transform becomes: Y = (0.257 × R) + (0.504 × G) + (0.098 × B) + 16, Cb = U = −(0.148 × R) − (0.291 × G) + (0.439 × B) + 128, Cr = V = (0.439 × R) − (0.368 × G) − (0.071 × B) + 128.

The YUV color model is used in the PAL, NTSC, and SECAM composite color video standards. The luma component is often denoted as Y', but sometimes as Y, prime symbols are often omitted in writing. The YUV system allows the transmission of color images over a channel intended for black-and-white (luma) signals, reducing the bandwidth needed. The black-and-white receivers still display a normal black-and-white picture, while color receivers reverse the process, decoding the UV portions of the signal and displaying a color picture.

One major advantage of YUV is that some of the information may be discarded in order to reduce bandwidth or when chroma is to be processed separately from luma. If only luma needs to be transmitted, that is, the U and V components are zero throughout the frame, then the data size is half of what it was before with no loss to perceived image quality. When converting from full color to YUV and back again, there is some loss of information due to rounding errors.

YUV subsampling is a method of encoding images by implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance. 4:4:4 full-resolution YUV stores no chroma subsampling, while common schemes are 4:2:2 (half resolution horizontally), 4:2:0 (half resolution horizontally and vertically) and 4:1:1 (one quarter resolution horizontally). 4:4:4 subsampling preserves all the information present in the original sample. The ratios describe how many luma and chroma samples are encoded for a block of pixels.

There are several shades of YUV color spaces used in video and digital photography systems. The main differences are the scale factors for the U and V planes in the basic equations. While the Y plane represents luminance, and thus requires higher bandwidth, the U and V planes can be bandwidth-reduced, subsampled, compressed, or otherwise treated separately for improved system efficiency. Thus there are several YUV formats, possibly using shades of 8-bit or 10-bit encoding for the planes.

The YUV color model has seen widespread use in digital video, including use in television standards like PAL, NTSC and SECAM, in MPEG compression, in modern digital video interfaces like HDMI, digital video compression schemes like H.264 and VP9, and common image/video container formats such as JPEG/JFIF, PNG and WebP. Its popularity is due to its usefulness in color compression and its ability to take advantage of human perception for more efficient storage and transmission. Overall, YUV remains one of the most important and widely used color models in digital imaging and video.