Fix printer error 0X00000926: already in use by spooler

When this error shows up

You're printing a document — maybe a PDF from Adobe Reader or an email from Outlook — and nothing comes out. You check the printer queue, but it's empty. You try again, and Windows pops up with: 0X00000926: This device is already in use by the spooler. You might also see NERR_InUseBySpooler in Event Viewer. This usually happens after a printer job got stuck, got cancelled, or the PC was rebooted while the spooler was mid-job.

What's actually happening

The spooler is a middleman between your app and the printer hardware. It writes print jobs to disk (spool files) and sends them out through a port (like USB001, LPT1, or a network port). When a job fails or gets aborted, the spooler sometimes leaves the port flagged as in use. The error code 0X00000926 is Windows telling you: I can't send this new job because I think the port is still busy with a previous one. It's a lock that wasn't released. The fix is to force-release that lock by restarting the spooler service and clearing its cache.

The fix

Skip reinstalling the printer driver — that's overkill and won't help because the problem is in the spooler's internal state, not the driver. Here's the real fix.

1. Stop the spooler service. Open Command Prompt as admin (right-click Start, then Command Prompt (Admin) or Terminal (Admin)). Run:
   net stop spooler
   Wait for the successfully stopped message.
2. Delete the cached spool files. In the same admin prompt, run:
   del /q /f /s %systemroot%\System32\spool\PRINTERS\*.*
   This removes all leftover .SPL and .SHD files — the stuck jobs that hold the port lock. If you get a file in use error, you probably missed step 1.
3. Start the spooler service. Run:
   net start spooler
4. Restart the print spooler dependency. This is the part people skip. Run:
   net stop spooler && net start spooler
   Wait 5 seconds, then try printing again. The double restart forces Windows to re-initialize port mappings.

If the error disappears but returns later, the port itself might be misconfigured. Go to Control Panel > Devices and Printers, right-click your printer, pick Printer Properties, then click the Ports tab. Note which port your printer uses (e.g., USB001, DOT4_001). If it's a network printer, the port name will look like IP_192.168.1.50. Delete any duplicate ports (same IP or USB number) — those confuse the spooler.

Still failing?

Check these:

• Event log clues. Open Event Viewer > Windows Logs > System. Filter by source PrintService. Look for event ID 808 (port conflict) or 811 (spooler crash).
• Third-party printer software. Some HP, Canon, or Brother utilities inject their own port monitor. Try uninstalling the manufacturer's toolbox — keep only the basic driver.
• USB port power saving. In Device Manager > Universal Serial Bus controllers, right-click each USB Root Hub, go to Power Management, and uncheck Allow the computer to turn off this device. The spooler hates when USB ports go to sleep mid-job.

That's it. The spooler is holding a ghost lock, and this clears it without nuking your printer setup.