What is HDCP? Screen mirroring, HDMI capture and your videos
What HDCP protects, why students see HDCP errors on projectors, why it doesn't stop every capture, and where mirroring rules clash with classrooms.
On this page 9 sections
HDCP, short for High-bandwidth Digital Content Protection, encrypts the video signal travelling from a device to a screen, for example over HDMI from a laptop to a TV or projector. Before protected content plays, the device checks that the screen, and anything in between, is licensed to receive it; if that check fails, you see a black screen or an "HDCP error". For course owners, HDCP can stop ordinary HDMI capture devices recording protected playback, but only when the player asks for it, not every device follows the rules, and it regularly trips up legitimate classroom projectors.
What HDCP does
HDCP protects the last cable, not the video file. Three kinds of device take part:
- Transmitters send the video: laptops, phones, streaming sticks, set-top boxes and Blu-ray players.
- Receivers display it: TVs, monitors and projectors.
- Repeaters sit in between and pass it on: AV receivers, switches, splitters and some extenders.
When protected content starts, the source checks that every device in the chain is licensed, then encrypts the link. If any device fails the check, the source refuses to send the protected picture. HDCP was developed by Intel and is licensed by Digital Content Protection LLC, whose HDCP FAQ puts the distinction neatly: "HDCP is not DRM; it is copy protection." DRM decides whether you may watch; HDCP secures the cable the picture travels over.
HDCP is switched on by the content, not by the cable. A streaming app or DRM licence says "this video needs HDCP"; ordinary desktop use, a slide presentation or a typical web video doesn't ask for it, so the same HDMI link carries those unencrypted.
HDCP versions: 1.4, 2.2 and 2.3
| Version | Specification | Where you'll meet it | What to know |
|---|---|---|---|
| HDCP 1.4 | 2009 | Older TVs, monitors and projectors; HD content | Common on older displays, but not enough for protected 4K |
| HDCP 2.2 | 2012 | 4K TVs, streaming devices and consoles | Generally required for 4K streaming |
| HDCP 2.3 | 2018 | Current TVs, monitors and graphics hardware | The latest revision of the 2.x family |
HDCP 2.x is a separate design from 1.x, not a small update: DCP says mixing the two needs repeaters or active converters that have both kinds of interface. For 4K, services generally require HDCP 2.2; Netflix, for instance, asks for an HDMI connection that supports HDCP 2.2 or later. A 4K source won't send protected 4K video to a display that only supports 1.4, which is behind many "why won't this play in 4K?" complaints.
Why students see HDCP errors
An HDCP error means the protection check failed somewhere in the chain. The usual culprits:
- an older projector or monitor that doesn't support HDCP, or supports only 1.4 when the content needs 2.2;
- a splitter, switch, extender or cheap USB-C to HDMI adapter that doesn't pass HDCP;
- a capture device connected in the chain;
- a check that failed after the display went to sleep or changed input.
For honest students, the usual fixes are simple: connect the device directly to the display, replace the adapter or cable with one that states HDCP support, turn the display on before the source, update the display's firmware, or try a display that supports HDCP 2.2.
Why HDCP doesn't stop every capture
An HDMI capture device records whatever arrives on the cable, which is why HDCP matters for piracy: devices that follow HDCP's rules won't record a protected signal. But HDCP falls short in three ways.
- It only applies when the player asks for it. Video that isn't played through protected playback goes over the cable unencrypted, and a capture device can record it. Blocking screen recording inside an app doesn't change that, as our guide to screen capture on Windows and Mac explains.
- Not every device follows the rules. Equipment that ignores HDCP exists, so HDCP raises the bar rather than closing the door.
- It isn't unbreakable. In 2010 an HDCP master key was published online, and Intel confirmed to CBS News that it was genuine, while saying the technology would remain effective.
And like every protection that stops at the screen, HDCP does nothing about a phone camera pointed at the display. Deliberately getting around it to copy content can also be an offence: in India, Section 65A of the Copyright Act makes circumventing an effective technological measure that protects copyright, with the intention of infringing it, punishable with up to two years in prison and a fine.
Screen mirroring: easy to notice, hard to judge
Apps can usually tell when a screen is being mirrored or an extra display is connected. iPhone and iPad apps are told when the screen is being mirrored, sent over AirPlay or recorded; Android apps can see when another display is connected and whether Android treats it as secure; Windows apps can see the displays attached to the computer. Websites can tell very little.
The hard part is judging the signal. A student mirroring a paid lecture to a TV in a PG room and a teacher mirroring it to a classroom projector look the same to the app. Our guides to what FLAG_SECURE can't stop and iOS screen recording detection cover each platform's blind spots.
Where HDCP and mirroring rules cause trouble
| Situation | The problem |
|---|---|
| A teacher's laptop and a classroom projector | An old projector or adapter triggers HDCP errors, or mirroring rules block the class entirely |
| Recorded lectures shown at a franchise or study centre | One account on a big screen serves a whole room, and rules loosened for the centre may apply to everyone |
| A student mirroring to a TV | A paid lecture ends up on a screen you know nothing about |
| A student who needs a larger screen, for example for low vision | Blanket blocks turn into accessibility complaints |
Questions to ask a vendor
- Does playback in your apps require HDCP on external displays, and for which content?
- What does a student see when their display doesn't support HDCP, and how are they told to fix it?
- Can teachers and study centres use projectors while students can't mirror paid lectures?
- What happens when a student mirrors a lecture to a TV, on Android and on iPhone?
- What does a capture device on a laptop's video output record from your desktop app?
- Since HDCP can't stop a camera, how can a leaked copy be traced back to an account?
Key takeaways
- HDCP encrypts the link from device to screen and blocks protected video on unlicensed displays and capture devices.
- It only applies when the content or player requests it, and not every device follows the rules.
- HDCP errors usually come from old displays, splitters and adapters; connecting directly often fixes them.
- Mirroring is easy for apps to notice but hard to judge, because classrooms and pirates look alike.
- Nothing about HDCP stops a camera pointed at the screen.
For why protected streaming video often records as a black rectangle, see why recordings go black, and for how device security levels affect this, Widevine security levels.
This is general information, not legal advice. For your situation, speak to a lawyer.
VidSafe, the video protection built by Upclass, combines VidSafe proprietary encryption with screen- and camera-recording detection, dynamic watermarking and account-sharing prevention. VidSafe adds visible and invisible watermarks that are extremely hard to remove, even after heavy re-encoding, so a leaked copy can be traced back to the account it came from. See Upclass pricing.
Frequently asked questions
What is HDCP support in monitor?
A monitor with HDCP support can receive and display HDCP-protected video, such as streaming films or Blu-ray, over HDMI or DisplayPort. Without it, protected content shows a black screen or an error. For 4K streaming, the monitor and every device in between generally need HDCP 2.2 or later. Everyday computer use works on any monitor, with or without HDCP.
What is HDCP content protection?
HDCP content protection is encryption applied to the video signal between a source device and a display. Before sending protected content, the source checks that the display is licensed and then encrypts the link, so a recorder that follows the rules gets nothing usable. It protects the connection only: once the picture is on the screen, a camera can still film it.
Can screen mirroring be detected?
Yes, by apps. iPhone and iPad apps are told when the screen is being mirrored or recorded, and Android apps can see when another display is connected. Websites can detect very little. The harder problem is deciding what to do, because a student mirroring to a TV and a teacher mirroring to a classroom projector look the same to the app.