cnbjmon.dll Not Found: Repair Canon Printing on Windows

cnbjmon.dll is a legacy Windows print-monitor file associated with older Canon Bubble-Jet printer drivers. If Windows says cnbjmon.dll is missing, cannot load, or contains an error, repair the Canon printer installation and Print Spooler before attempting any general DLL fix.

The file description is historically recorded as “Langage Monitor for Canon Bubble-Jet Printer”, including the misspelling of “Language.” It is part of the Microsoft Windows operating system, but its job is specifically tied to Canon printer communication.

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What is cnbjmon.dll?

cnbjmon.dll is a printer language monitor DLL. Microsoft describes language monitors as user-mode components loaded by the Print Spooler to communicate with compatible printers and add printer-control information to print jobs.

The file is therefore not a Visual C++ runtime, DirectX component, .NET library, or game dependency. It belongs to the Windows printing path and was used by older Canon BJ and Bubble-Jet printer packages.

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Microsoft supplied the Windows print-monitor component, while Canon printer-driver packages registered or used it. That is why an error can identify a Microsoft file while appearing only when a Canon printer is installed.

Historical records associate the file with the BJ Language Monitor print-monitor entry and with older Windows directories such as C:WindowsSystem32. Those records do not prove that the same DLL is a normal inbox file on every current Windows 10 or Windows 11 installation. Do not copy a historical file into both System32 and SysWOW64 based on a download-site instruction.

Why Windows reports the error

The Print Spooler loads printer monitors when it starts a print job, enumerates an installed printer, or processes a printer-driver configuration. An error involving cnbjmon.dll can therefore appear when you:

• Start or restart the Print Spooler
• Add an old Canon printer
• Print a document
• Reinstall or update a Canon driver
• Remove a printer incompletely
• Restore an old system image
• Run disk cleanup or security software that removed a file
• Install a Windows update while an old printer package remains registered

Common Windows loader variants include:

• “The program can’t start because cnbjmon.dll is missing from your computer.”
• “cnbjmon.dll was not found.”
• “The code execution cannot proceed because cnbjmon.dll was not found.”
• “cnbjmon.dll is either not designed to run on Windows or it contains an error.”

The exact wording depends on which process attempted to load the file. A missing-file message, a bad-image message, and a Print Spooler crash do not necessarily have the same cause.

First, identify the type of failure

Before repairing anything, note when the error appears.

A 32-bit legacy printer DLL is not made compatible with 64-bit Windows simply by placing it in another directory. The printer driver, monitor, architecture, and Windows release must work together.

Fix 1: Remove and reinstall the Canon printer driver

This is the most likely fix when the error appears during printing, printer installation, or Print Spooler activity.

Remove the printer

1. Open Settings.
2. Select Bluetooth & devices.
3. Select Printers & scanners.
4. Select the affected Canon printer.
5. Choose Remove.
6. Confirm the removal.
7. Disconnect the printer if it is connected by USB.

If the printer is listed more than once, remove each obsolete copy. Old queues can retain references to a printer monitor even after the physical printer has been disconnected.

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Remove the device and driver package

1. Right-click the Start button.
2. Select Device Manager.
3. Open the View menu.
4. Select Show hidden devices.
5. Expand Printers, Print queues, and any Canon-related category.
6. Right-click the affected device.
7. Select Uninstall device.
8. If Windows offers Delete the driver software for this device, select it.
9. Confirm the removal.

The delete-driver option is not available for every device. If Windows does not show it, continue with the printer removal and restart. Windows may otherwise rediscover and reinstall an old package automatically.

Reinstall the correct package

1. Restart Windows.
2. Open Canon’s official support portal.
3. Search for the exact printer model and regional product name.
4. Select the driver for the Windows version and architecture shown in Settings > System > About.
5. Download the complete printer-driver package from Canon.
6. Run the installer as instructed.
7. Reconnect the printer only when the installer requests it.
8. Print a test page.

If the test page prints without the DLL message, the stale printer package was the cause. If the installer itself reports that cnbjmon.dll cannot load, remove the remaining Canon software and driver entries again before trying a compatible package.

Outbyte Driver Updater can reduce the manual work of hunting through driver versions and identifying which device package is stale; its free scan shows what it finds, while driver installation is handled by the full version. It is optional, and the exact Canon driver or a generic Windows driver remains the proper fix when the printer model is obsolete.

Fix 2: Run DISM and System File Checker

Use Windows repair commands when the file may be missing from a protected Windows component, when several system components are failing, or when reinstalling the printer does not resolve the problem.

Microsoft recommends running DISM before SFC because DISM repairs the Windows component store that SFC uses as a repair source.

Run DISM

1. Open Start.
2. Type Command Prompt.
3. Right-click Command Prompt.
4. Select Run as administrator.
5. Approve the User Account Control prompt.
6. Run:

DISM /Online /Cleanup-Image /RestoreHealth

Wait for the operation to finish. Do not close the window if the progress appears to pause.

Run SFC

After DISM completes, run:

sfc /scannow

Allow the scan to reach 100 percent. Then restart Windows and test the printer again.

Possible SFC results include:

• Windows Resource Protection did not find any integrity violations: no protected-file corruption was found.
• Windows Resource Protection found corrupt files and successfully repaired them: restart and test printing.
• Windows Resource Protection found corrupt files but was unable to fix some of them: inspect the CBS log and continue with printer-driver repair or Windows recovery.

The relevant log is:

%windir%LogsCBSCBS.log

Do not manually replace cnbjmon.dll with a file from an unrelated computer. A controlled replacement would require a verified copy matching the Windows version, architecture, language, and servicing level.

When repeatedly running DISM and SFC does not make clear what changed, Outbyte PC Repair can provide an optional scan that identifies system issues; its free scan reports findings, while repair is performed by the full version. It is not required, and DISM followed by SFC remains Microsoft’s built-in repair path.

Fix 3: Restart and check the Print Spooler

A damaged queue or stale monitor entry can keep triggering the error.

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Restart the service

1. Press Windows key + R.
2. Type services.msc.
3. Press Enter.
4. Find Print Spooler.
5. Right-click it.
6. Select Restart.

If the service stops immediately or crashes again, do not repeatedly restart it without removing the problematic printer driver. The driver may be loading the monitor as soon as the service starts.

Clear stuck print jobs

Only clear the queue if pending jobs are preventing removal or testing.

1. In Services, right-click Print Spooler.
2. Select Stop.
3. Open File Explorer.
4. Go to:

%windir%System32spoolPRINTERS

1. Delete the files inside that folder, not the folder itself.
2. Return to Services.
3. Right-click Print Spooler.
4. Select Start.

Try printing again. If the spooler crashes after the Canon printer is reinstalled, remove that driver and test with a generic or in-box driver.

Fix 4: Use a generic printer driver

An older Canon driver may not support the current Windows architecture or release. This can produce a bad-image error even when a file with the right name exists.

After removing the Canon package:

1. Open Settings > Bluetooth & devices > Printers & scanners.
2. Select Add device.
3. Allow Windows to search.
4. If the printer is not found, choose the option to add it manually.
5. Select a connection method appropriate to the printer.
6. Choose a compatible generic or Microsoft in-box driver when offered.
7. Complete installation.
8. Print a test page.

A generic driver may not provide Canon-specific status features or advanced print controls, but it can confirm whether the old Canon monitor is causing the failure. If generic printing works, the original Canon driver is the likely source.

If no compatible driver exists, the practical choices are the printer’s original installation media, a vendor driver specifically supporting the current Windows release, a generic driver, or replacement of the obsolete printer.

Fix 5: Check antivirus quarantine safely

Security software may quarantine a file after a scan, particularly when an old driver package contains outdated components.

1. Open your antivirus or Windows Security application.
2. Open Protection history or Quarantine.
3. Search for cnbjmon.dll.
4. Check the original file path.
5. Check whether the file has a valid Microsoft digital signature.
6. Restore it only if it came from the expected Windows directory and the signature is valid.
7. Run a full malware scan.
8. Run DISM and SFC afterward.

Do not restore a file solely because its name matches. A malicious file can use the same filename. If the file came from a temporary folder, a download directory, or an unknown printer package, leave it quarantined and remove the associated software.

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How to verify the file

If a copy of cnbjmon.dll exists, verify its location and signature before trusting it.

1. Open File Explorer.
2. Browse to the file.
3. Right-click it.
4. Select Properties.
5. Open the Details tab.
6. Confirm that the description refers to the Canon Bubble-Jet language monitor.
7. Open the Digital Signatures tab if present.
8. Select the signer.
9. Choose Details.
10. Confirm that Windows reports the signature as valid.

The historical Windows location is commonly reported as C:WindowsSystem32, but a historical location is not proof that every current Windows installation should contain the file there. Do not copy it into arbitrary folders or place the same binary in both System32 and SysWOW64.

A missing signature, unexpected path, or mismatched architecture is a reason to distrust the file and repair the driver or Windows component instead.

Why regsvr32 usually does not help

regsvr32 is intended for DLLs that expose registration entry points such as DllRegisterServer. A print-monitor DLL is normally loaded by the Print Spooler through the printer-monitor configuration and initialization process.

Running:

regsvr32 cnbjmon.dll

is therefore not a normal repair for this file. It may produce an error, create confusion about which copy was loaded, or encourage placing the DLL in the wrong directory. Reinstall the printer package so its INF installer can create the appropriate driver and monitor configuration.

Why Visual C++, DirectX, and .NET repairs are irrelevant

Those packages do not provide the Canon Bubble-Jet print monitor. Reinstalling them is not a justified first response to a cnbjmon.dll error.

Use those repairs only when a separate application reports a dependency belonging to one of those runtimes. For this file, the relevant repair paths are:

• Canon printer-driver removal and installation
• Print Spooler cleanup
• Generic printer-driver testing
• DISM and SFC
• Windows recovery when system damage is severe

If the error began after an update or system restore

First install all pending Windows updates, restart, and repeat the printer test. An update can expose an incompatible legacy driver without meaning that Windows itself is missing a current runtime file.

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If the problem began immediately after a clearly identified update, driver installation, cleanup operation, or system restore:

1. Open Settings.
2. Go to System > Recovery.
3. Review the available recovery options.
4. Use System Restore only when a dated restore point matches the regression.
5. Reinstall the printer driver afterward if the restore removed it.

System Restore can remove recently installed drivers and applications. It should not be used as a substitute for removing a broken printer package.

If the Print Spooler still crashes

After removing the Canon printer and driver:

1. Restart Windows.
2. Start the Print Spooler.
3. Confirm that it remains running with no printers installed.
4. Add a generic printer driver.
5. Test printing.
6. If the spooler remains stable, add printers one at a time.
7. Identify which driver causes the crash.

Review Event Viewer under the Windows print-service and system logs around the crash time. Look for the printer driver or monitor loaded immediately before the failure. Remove that package and use a compatible vendor or generic driver.

If the spooler crashes even with all third-party printers removed, run DISM and SFC again, install pending updates, and consider Windows recovery or an in-place repair installation. Do not solve a persistent spooler failure by downloading another copy of the DLL.

What not to do

• Do not download cnbjmon.dll from a random DLL website.
• Do not copy an old file into System32 or SysWOW64 without verifying its source and architecture.
• Do not assume a Windows XP file is a current Windows 10 or Windows 11 component.
• Do not use regsvr32 as a generic DLL repair command.
• Do not reinstall Visual C++, DirectX, or .NET as the first response.
• Do not restore an antivirus quarantine item without checking its signature and original path.
• Do not edit the print-monitor registry entries manually unless you are following a controlled recovery procedure and have a backup.
• Do not keep reinstalling the same obsolete Canon driver if it repeatedly crashes the Print Spooler.

FAQ

Is cnbjmon.dll a Microsoft file or a Canon file?

It is a Microsoft Windows print-monitor component associated with Canon Bubble-Jet printers. Microsoft supplied the legacy Windows component, while Canon printer packages registered or used it.

Is cnbjmon.dll required by Windows 11?

A current, universal Windows 11 requirement has not been established. The file is strongly associated with older Windows and Canon printer installations. If Windows 11 reports it, investigate an old printer driver or spooler registration rather than assuming that the file must be downloaded.

Is it safe to download the DLL?

No. Random DLL sites can provide malware, an altered file, the wrong Windows version, or the wrong architecture. Even a genuine file may not repair the printer package that is requesting it.

Should I copy it into SysWOW64?

No. Directory placement depends on Windows architecture and the complete driver package. Copying a 32-bit DLL into an arbitrary directory does not make an incompatible printer driver work.

Will SFC repair it?

SFC can repair a damaged protected Windows file when a valid component-store copy is available. It will not repair an obsolete Canon driver or an incompatible printer monitor. Run DISM first, then SFC.

What if Canon no longer offers a driver?

Try the original installation media, a compatible vendor package, or a generic in-box Windows printer driver. If the printer cannot work with any compatible driver, replacing the obsolete printer may be more reliable than forcing a legacy monitor onto a current Windows installation.

What is the safest repair order?

Remove the affected Canon printer and driver, restart Windows, install a compatible official driver, and test. If the error remains or affects the wider system, run DISM followed by SFC. If the Print Spooler still crashes, remove the legacy driver and test with a generic printer driver.

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