What is EDID? EDID, short for Extended Display Identification Data, is the information a monitor sends to your computer to say what it is and what it can show. It covers the maker, the supported resolutions, and the refresh rates. Your computer reads it when you connect a display and uses it to pick a picture setting. When the data is missing, your computer can fall back to a low resolution or show no image, and when the monitor drops out and returns, Windows can treat it as unplugged and rearrange your windows.
Quick answer: EDID is a small data block a monitor sends to your computer to report its maker, supported resolutions, and refresh rates. The computer asks for it when a hot plug signal says a display is connected. If EDID is lost, you may see no picture or a low resolution, and Windows may move your windows. The Gitfos C1Pro Smart Button can turn off the HDMI picture while keeping EDID.
What EDID is and who defined it
EDID is a standard that lets a display describe its own capabilities to a source device. VESA, the display standards body, introduced version 1.0 in 1994. The original structure is 128 bytes, a later version added a 256-byte structure, and E-EDID adds optional 128-byte extension blocks, as Extron's EDID guide explains.
What information EDID contains
EDID holds identity details and a list of picture modes the monitor can show. The original 128-byte block has five main parts.
| Part | Where in the block | What it tells the computer |
|---|---|---|
| Manufacturer and product | First 18 bytes | Maker, product, serial number, manufacture date |
| Basic parameters | Bytes 20 to 24 | Digital or analog input, display size, gamma, power management |
| Established timings | Bytes 35 to 37 | Common VESA modes such as 640 x 480 at 60 Hz |
| Standard timings | Bytes 38 to 53 | Eight more VESA resolutions |
| Detailed timings | Bytes 54 to 125 | Four custom modes, including the preferred one |
Extension blocks add more video formats and multi-channel audio capabilities.
How your computer reads EDID
The computer asks for EDID when it sees a hot plug signal. The monitor sends a voltage on a hot plug detect (HPD) pin to say it is connected. When the computer senses that voltage, it requests the EDID over a small data line called DDC. HDMI, DVI, and DisplayPort support HPD. VGA does not.
What happens when EDID is lost
When EDID is lost, you can get a wrong picture or no picture at all. Extron lists three outcomes.
- No image, because the source will not output video without EDID.
- A fallback to 640 by 480, which makes text look oversized, undersized, or blurry.
- With several displays, a mismatch, because a PC may read EDID from only one of them.
Why EDID moves your windows
If a monitor stops reporting itself, Windows can treat it as unplugged and move your windows to the remaining screen. A monitor that sleeps or is switched off can drop its hot plug and EDID signals. Microsoft calls this behavior Rapid Hot Plug Detect. For the full set of fixes, read why windows rearrange when the monitor turns off.
How to keep EDID alive
Two things keep a computer believing a display is connected: a device that holds EDID, or a hub that does it for you.
- An EDID emulator sits in the video path and keeps reporting a display.
- The C1Pro Smart Button, on a single click with the blue light off, turns off the HDMI picture but keeps EDID, so Windows still sees the monitor and your layout stays put.
| C1Pro item | Spec | Why it matters here |
|---|---|---|
| HDMI output | 1 port, 4K @ 60Hz | The only port that carries video |
| Smart Button, single click | HDMI picture off, EDID kept | Window layout stays in place |
| Power | 65W DC adapter, required | The hub does not run without it |
What EDID does not do
EDID describes a monitor's abilities, and it does not guarantee that a connection can carry them.
- EDID does not add bandwidth. A cable or port that cannot carry 4K at 60Hz still cannot, even if the monitor lists it.
- The Smart Button covers a screen you blank from the hub. If your monitor drops its own signal when it sleeps, use the Windows 11 setting or another fix instead.
- The USB ports on the C1Pro do not output video. Only the HDMI port does.
- The C1Pro needs its 65W DC adapter connected. It has no bus-powered mode.
Frequently asked questions
Most EDID questions come down to the handshake between a monitor and a computer.
What is EDID?
EDID stands for Extended Display Identification Data. It is a standard way for a monitor to tell your computer what it is and what it can show, including its maker, supported resolutions, and refresh rates. VESA introduced it in 1994.
What information does EDID contain?
It holds the manufacturer and product ID, serial number, manufacture date, basic display parameters, a list of supported resolutions and refresh rates, and the monitor's preferred timing. Extension blocks can add more video formats and audio capabilities.
What happens if EDID is missing or unreadable?
The computer may output no image, or fall back to a low resolution such as 640 by 480. Text can then look oversized or blurry. If the display drops out and returns, Windows may also treat it as unplugged and move your windows.
What is hot plug detect?
Hot plug detect, or HPD, is a signal the monitor sends to say it is connected. When the computer sees it, the computer asks for the EDID. HDMI, DVI, and DisplayPort support it, and VGA does not.
What is an EDID emulator?
An EDID emulator is a small device that sits in the video path and keeps reporting a display to the computer, even when the real monitor is off or unplugged. It stops Windows from treating the display as removed.
Next steps
If your windows jump around, start with the Windows 11 setting in the window rearrange guide. To check your refresh rate, read USB-C hub 4K 60Hz vs 4K 30Hz. For a hub that keeps EDID with one click, see the Gitfos C1Pro, browse more hubs and charging options, or reach the team through the support center. More fixes live in the Support blog.