CAC reader not working on Windows 11 or 10

Windows 10 and 11 have smart card support built in, so most CAC readers work without extra software. When one stops working (often right after a Windows update) the cause is usually one of three things: the reader, the Windows Smart Card service, or missing DoD certificates. Work through them in order.

1. Hardware basics

• Insert the CAC chip-first, chip facing up, all the way in.
• Plug the reader straight into the computer. Try another USB port and skip unpowered hubs and docks.
• Unplug the reader, restart Windows, then plug it back in.
• If Windows still doesn't detect the reader, install the current driver from the reader manufacturer's own website.

2. Check the Smart Card service

Windows talks to readers through the Smart Card service (SCardSvr). Microsoft's smart card debugging guide uses these checks:

1. Open Command Prompt and run sc queryex scardsvr. It should report STATE : 4 RUNNING when a reader is connected.
2. If it isn't running, open Command Prompt as administrator and run net start scardsvr (or net stop scardsvr then net start scardsvr to restart it).
3. Run certutil -scinfo with your CAC inserted. It should list the reader and your card's certificates. Microsoft notes no PIN is needed for this; press Esc if a PIN prompt appears.

On a government-managed computer, don't change services yourself. Contact your IT help desk.

3. Card detected but sites still fail

• If certutil -scinfo sees your card but sites give "not trusted" or "connection not private" errors, install the DoD root certificates with InstallRoot. See the DoD certificates guide.
• Fully close and reopen the browser after installing certificates.

4. Things you can't fix at home

• A locked PIN or expired certificates need an ID card office. See CAC PIN locked or forgotten.

Related

• CAC reader setup basics · CAC reader on Mac
• Logins that need a working reader: AVD, MyPay, DTS, Army webmail.