No spare monitor? Your phone can be the screen for any PC or server - all it takes is a small HDMI capture card and the right connection order.
The monitor is dead, the server has no screen, or you are standing in front of a PC at a site with nothing to plug in - and the machine in your pocket is a perfectly good display. This guide builds the complete setup: PC HDMI out, capture card, OTG adapter, phone. Watch the video above for the live demo, and use this page as the checklist.
A capture card is a small converter. On one side it takes an HDMI signal - the same picture a monitor would show. On the other side it hands that picture to a phone or computer as a standard USB camera feed, a format called UVC. Your phone thinks it is looking at a webcam. In reality it is looking at your PC's screen.
That one trick is why this setup is so useful. The PC needs no software, no driver and no network for this to work. It does not even need an operating system running - the HDMI port sends a picture from the moment the machine powers on. A headless server, a PC with a dead monitor, a machine stuck in BIOS - if it has HDMI out, your phone can be its screen.
Four things, and one of them decides whether the whole plan works at all:
Order matters with USB devices. Follow this sequence exactly:
If the app was already open before you plugged in, close it fully and open it again - many viewer apps only look for USB devices at start.
The phone shows whatever the HDMI port sends, so picture problems are fixed on the PC, not in the app. If the image is stretched or cut off, set the PC's display resolution to 1920 x 1080 or lower - small phone screens make 1080p text perfectly readable, and cheaper capture cards cannot accept higher input anyway. If the PC is also connected to a real monitor, choose Duplicate in display settings so both screens show the same picture.
One honest limit: most budget capture cards deliver 1080p at 30 frames per second, sometimes less. That is plenty for setup screens, BIOS and checking a server. It is not a gaming display - the lag and frame-rate pages in this series explain why, in numbers you can trust.
Before you rely on this setup at a client site or on a server, prove it end to end at home:
If all four pass, you own a monitor that fits in your pocket and works on any machine with an HDMI port.
Honesty first, because this trick is easy to oversell. The phone is a display only. Touching the phone screen does nothing to the PC - your keyboard and mouse stay plugged into the PC itself. It also cannot show a picture from a PC whose HDMI port itself has failed, and it cannot fix a machine that sends no signal at all - it only proves that quickly, which is itself valuable diagnosis.
And this is a different tool from the software second-screen apps. Those extend a working Windows desktop over Wi-Fi. This capture route shows any HDMI signal, including BIOS, on a machine that may have no working system at all. The comparison page in this series separates the two honestly.
The video shows the full live setup - the card, the adapters, the app and the first picture on the phone screen.
Watch Full VideoNo. The phone must support USB OTG and external USB cameras (UVC). Most mid-range and flagship Android phones do, but some budget models leave OTG out or block USB cameras. There is no app that adds missing hardware support, so test your phone with any USB device first if you are unsure.
Nothing at all. The PC only sends its normal picture out of the HDMI port. No driver, no software, no network and not even a working Windows is needed - which is exactly why this works for BIOS screens and headless servers.
No. This route is display only. The capture card carries picture in one direction, from PC to phone. Your keyboard and mouse stay connected to the PC. For control from the phone you would need a remote desktop tool, which is a separate setup that needs a working system and a network.