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Is there any monitor that can send the DPI info to the computer using Display Data Channel or similar?

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You are right, monitors do not send DPI information.

But EDID (Extended Display identification Data), which is transmitted via DDC (Display Data Channel), contains both the timing information (the resolution) as well as the physical screen size, so software can calculate the monitor's DPI (or better: its pixel density, normally measured in PPI) using these values.

The display's rough physical size information is represented in EDID as Horizontal Size (in centimeters, at offset 21) and Vertical Size (in centimeters, at offset 22) and, more precise (in millimeters), in the Detailed Timing Descriptor Blocks at offsets 12 to 14 (Horizontal Display Size and Vertical Display Size).

The display's resolution is stored in the Detailed Timing Descriptor Blocks, beginning at offset 54 (Horizontal Active Pixels and Vertical Active Lines).

Side note:

One can expect that the resolution information is correctly programmed in all monitors because this value is used by the operating system to correctly set the screen resolution. The size information however can be wrong or even completely missing because it is not a hard requirement (or not even needed) for setting the screen resolution correctly.

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  • The EDID does contain size in millimiter precision. Check bytes 12-14 of the timing descriptor block. – Ofek Shilon Oct 11 '17 at 21:38
  • If the DPI can be calculated. It is enough for me. Thank you! – Eduardo Oct 12 '17 at 21:23
  • The screen size info in the EDID is routinely ignored by both Windows and Linux system software. Users, especially those with high-DPI monitors, have been complaining about that fruitlessly for years. – kreemoweet Oct 12 '17 at 23:46
  • Can EDID contain information on the recommended DPI scaling? or Expected viewing distance? Windows 10 has per monitor DPI scaling. It determines recommended DPI scaling based on various factors - physical size, resolution, expected viewing distance. – Sahil Singh Aug 9 '19 at 7:25

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