• ✅ 2.1 | ✅ 2.0 | ✅ 1.9 | ...

  1. General Questions
  2. Minimum Requirements
  3. Known Issues
  4. Troubleshooting



  • When you purchase Premium Support you are granted the ability to generate a digital certificate and a public/private key pair to suppress all warning dialogues. This certificate has:

  • No client/user limitations

  • No domain restrictions

    A single license will suffice for 99% of organizations

  • The purchase of the premium version also provides technical support for one year. The Technical Support Team of QZ Industries, LLC will work diligently to help integrate the software into your environment. All questions are promised to be answered as fast as possible (usually well within a 24-hour period).

Suppressing Warnings

  • In order to suppress print warning dialogues, all print requests must be signed using the Intermediate Certificate and private key. An in-depth tutorial explaining how to do this can be found here.

QZ Tray Cost

  • QZ Tray is free. Organizations wishing to print silently are required to purchase a certificate from QZ Industries, LLC or implement their own root certificate. Pricing options can be found on QZ's homepage at

Installing New Version

  • Installation of a new version will succeed even if an older version is present and/or running.
  • Note: QZ Tray 2.0 is not backwards compatible with QZ tray 1.9.

Browser Managed By Organization

Question: Does QZ Tray make changes to the browser?

Yes. For normal QZ Tray operations a few, small changes are needed, please see below:

  • QZ Tray makes the following browser changes for proper operating:
    • Google Chrome:
      A policy file is installed to the system to allow qz:launch URLs to open without prompting the user
      • Windows: HKLM\SOFTWARE\Policies\Google\Chrome\URLWhitelist
      • MacOS: /Library/Preferences/
      • Linux: /etc/opt/chrome/policies/managed
    • Firefox:
      A policy file is installed to the system to allow Firefox to use the computer's certificate store.
      • All Operating Systems: <FIREFOX INSTALL>/distribution/policies.json
      • ESR Firefox Versions: <FIREFOX INSTALL>/firefox-config.cfg

Minimum System Requirements

Java Versions

Product Minimum Version
QZ Tray 2.2 OpenJDK 11 (bundled)
QZ Tray 2.1 Java 8 / OpenJDK 1.8*
QZ Tray 2.0 Java 7 / OpenJDK 1.7*
QZ Tray 1.9 Java 7 / OpenJDK 1.7
QZ Print 1.9 Java 6 / OpenJDK 1.6

*HTML printing in QZ Tray 2.x requires Java 8 + Java FX.

Operating Systems

Operating System Minimum Version
Apple OS X OS X 10.7 Lion or higher*
Microsoft Windows Windows XP or higher*
Linux Ubuntu 12.04 Precise or higher

Version 2.0 or higher requires 512MB of free memory (RAM), recommends 6GB or higher total system memory for raster graphics.

*Safari 5.1.7 is bundled with Lion but is not supported. Alternate browser required.
*Windows XP requires manual certificate installation. Will prompt at install time.

Web Browsers

Web Browser Minimum Version
Safari Safari 6.0.3 or higher
Firefox Firefox 31 or higher*
Chrome Chrome 31 or higher
Internet Explorer IE 10 or higher*
Microsoft Edge 20.x or higher*

* Firefox requires a browser restart for HTTPS
* IE/Edge on domain networks require external DNS access to due to a Local Intranet Limitation.

Known Issues

Conflicting Applications

The following applications may cause issues with QZ Tray installation.

  • Older Java versions: QZ Tray works best with Java 11 or higher. Older QZ Tray versions may conflict with QZ Tray and cause it to fail to start.

    • If possible, uninstall all versions of Java, JRE, JDK or OpenJDK from the system.
    • If uninstalling old versions of Java is not possible, install QZ Tray 2.2 or higher, which will come bundled with its own Java version.
  • Antivirus Software: Some antivirus applications may prevent QZ Tray from installing or running.

    • Comodo Antivirus will force application containment the QZ Tray installer and prevent it from being installed, uninstalled and prevent it from running. Moreover, disabling Comodo will have very little effect because it will re-enable itself without warning. QZ Tray is not supported with Comodo Antivirus.
  • Other Antivirus:

    • Application containment: If the antivirus forces application containment, please disable this application containment for QZ Tray and the Java Runtime which it uses.
    • Web Filtering: If the antivirus blocks access to local ports or localhost certificates, please disable or whitelist https://localhost:8181, http://localhost:8182.
    • Temporary File Access: If the antivirus blocks access to the temporary directory, please disable or whitelist the QZ Tray installer.
    • Other issues: QZ Industries does not provide support for issues created by third party antivirus applications. Built-in features (such as Windows Defender) are supported and may be escalated to the various support channels.


Installation Issues

  • If QZ Tray fails to install with the error "Sorry, this version of QZ Tray cannot be installed on this system"
    • This could be caused by mismatched architecture. QZ Tray is only supported on 64-bit Intel and 64-bit ARM/Apple Silicon. Please ensure the version you are installing matches your architecture.
    • This could be caused on Windows if the username has not ANSI-characters in the username. For example, Sørina may cause the installer to fail, whereas Sorina will succeed. This is a limitation of Java, but a workaround is available in issue #1095.
    • This could be caused on Windows if the username has an exclamation mark in it. For example, Lenovo! may cause the installer to fail, whereas Lenovo will succeed. This is a limitation of Java. No workaround is available, the software must be installed using a different user account without the exclamation mark.
    • This could be caused on a computer running a 32-bit operating system. No workaround is available. Older 2.1 versions may work with 32-bit Java runtimes, but this configuration is not officially supported.

Debugging QZ Tray

  • To automatically retrieve the logs:
    • From the QZ Tray Icon:
      Advanced, Troubleshooting, Zip Logs (To Desktop)
      (They will be placed on the Desktop in a ZIP file)

  • To manually retrieve the logs:
    QZ Tray places log files in the following locations:
    • Windows: %APPDATA%\qz
    • Mac: ~/Library/Application Support/qz
    • Linux: ~/.qz
Console Logs
  • The recommended approach for getting verbose output from QZ Tray is to launch the software from command line. This will expose the Java Console with detailed information about debug messages and exceptions including full backtrace of where a particular exception occurred.

  • QZ Tray launches with 512MB of memory. We must specify -Xms512M in the command in order to prevent unexpected behavior and crashing. This unnecessary for Mac unless following the basic syntax (java -jar qz-tray.jar) . More memory can be allocated but should not be necessary.

    Windows (after closing all instances of QZ Tray)

    "%PROGRAMFILES%\QZ Tray\qz-tray-console.exe"
    REM or for 2.1 and older: java -Xms512M --add-exports java.desktop/sun.swing=ALL-UNNAMED -jar "%PROGRAMFILES%\QZ Tray\qz-tray.jar"

    Mac OS X (after closing all instances of QZ Tray)

    /Applications/QZ\\ Tray

    Linux/Other (after closing all instances of QZ Tray)

Proxy configuration

Organizations utilizing a proxy for network access may experience connectivity issues with QZ Tray.

  • QZ recommends adding proxy exceptions to network resources required by QZ Tray
  • Alternatively, QZ Tray's Java instance may be coerced to use the system proxy by setting in <APP DIR>/runtime/conf/
PKIX Build Path Failed

Sometimes a message java.lang.UnsupportedOperationException: Cannot parse (FILE) will appear. This is often a failure by Java to download the specific resource and it will be followed by Caused by: PKIX path building failed

  • To fetch detailed HTTPS/SSL certificate information, append -verbose before the -Xms512 command. The output will be very large, you may redirect it to file using > file.log 2>&1 at the end.
  • See also
  • Common Causes
    • Broken certificate chain Remedy: Check validity, fix chain per CA instructions.
    • Self-signed certificate Remedy: Add an exception to Proxy or Firewall for this address -- OR -- Install certificate into Java.
    • Newly-trusted CA Remedy: Update Java. This is fairly common for LetsEncrypt certificates.
  • Possible remedy: Add to the command line options.

Crash During Printing

Cannot Launch Software

  1. A corrupt Java installation may prevent the software from installing or loading. A corrupt Java installation is fairly common in Windows, and can be resolved by reinstalling Java using the Java offline installer. The offline installer has been reported to fix many issues with corrupt Java installations. Take a look at this guide for our recommended steps on reinstalling Java on all platforms.

    Signs of a corrupt Java install:

    Creating keystore for ws://localhost...
    - [failed] Creating a CA keypair...

    ... or ...

    java -version
    "An error has occurred while processing the shared archive file. Unable to unmap shared space. Error occurred during initialization of VM. Unable to use shared archive."

  2. Sometimes custom JAVA_HOME environmental variables will prevent QZ Tray from loading. If the software can be launched via the command line this is likely the case. In windows this can be checked by going to System > Advanced system settings > Environment Variables

  3. HTML printing (JavaFX) can cause printing to fail if the following is true:

    • Issue: HTML page width is set to 100%.
      Remedy: Hard-code an acceptable page with using CSS, e.g. 800px
    • Issue: Printer resolution for HTML print is high (e.g. 600dpi, 1200dpi).
      Remedy: Hard-code a lower DPI (e.g. 300dpi) using { units: 'in', density: 300 }. We also recommend setting a sane fallbackDensity incase 300dpi is unsupported by certain hardware.
    • Issue: Out of memory issues can occur if running the 32-bit JVM.
      Remedy: See 32-bit vs. 64-bit: section below.
    • Issue: java.lang.NoClassDefFoundError: javafx/print/PrintColor at qz.printer.PrintOptions$ColorType
      Remedy: JavaFX is not distributed with all Java versions. Please install JavaFX for your platform (e.g. openjfx, etc).
  4. Images/PDFs cause software to stop working: More commonly Cannot call method public void, this is generally a sign that the JVM has hit an unrecoverable error. The most common cause is large print operations on a 32-bit JVM. A temporary workaround is to specify { rasterize: false } in the configuration, but this will only fix PDFs. A permanent solution is to switch to a 64-bit JVM which allocates a larger heap space. If 32-bit is required, additional heap space may be allocated via command-line.

  5. 32-bit vs. 64-bit: Some 64-bit workstations have both 32-bit and 64-bit Java versions installed. If both are needed, make sure both are upgraded, otherwise, removing the 32-bit version is advised to assist with the troubleshooting process.

  6. Insufficient Java Version "A Java Exception has occurred" may appear if attempting to launch against an outdated Java version. For a list of minimum Java requirements see Java Versions. May also be reported as Could not find the main class Program will exit.

  7. Disk Corrupted: Always try fsck (Linux), Disk Utility (MacOS) or chkdsk (Windows). Physical drives can show strange symptoms when they are beginning to fail however SSDs hard drives are susceptible to a condition called "worn bits" or more properly "SSD Endurance" which is responsible for re-using NAND flash memory. This process should be self-healing but on occasion can cause issues with certain drive firmwares. Make sure to scan your disk for health when encountering launch issues.

Cannot List Printers

  1. Mac

    Due to an upstream bug with Java, printer listings may fail on Mac.

    The current workaround is to:

    • Open System Preferences
    • Printers and Scanners
    • Right Click > Reset Printing System
    • Re-add all printers

    We realize this is not ideal, but have found no another work-around on Mac.

  2. Windows

    Although rare, there are scenarios of not being able to list printers, only being able to list one printer, or listing printers takes several minutes to complete. This is likely caused by a driver conflict between the offending printer driver and the print spooler, resulting in the entire print subsystem to hang.

    The workaround is to remove the offending printer or printer driver.

Raw Printer Queues

If your thermal or label printer has undesired results, it may be improperly configured. Here are our tutorials for setting up a printer to receive raw languages on each platform:

Note: Some Windows drivers, such as Zebra's ZDesigner driver for Microsoft Windows, will support raw printing alongside pixel-based/PostScript printing. You may use those drivers or a raw-generic/text-only driver to send raw commands, but the generic driver will not be able to print images/PDF/HTML.

Debugging WebSockets

By default, QZ Tray suppresses verbose websocket information from the console, however occasionally this information may be useful for debugging/troubleshooting connectivity issues.

Debugging WebSockets in 2.x
  • 2.x - Using the qz.api.showDebug(...) API option, verbose connection details will logged to the browser's console.

    qz.api.showDebug(true);  // must be called prior to calling qz.websocket.connect()
Debugging WebSockets in 1.9
  • 1.9 Only - Using the deployQZ(...) API option, verbose connection details will logged to the browser's console.

     deployQZ(null, true);  // usage: deployQZ(hostname, debug);

Socket Disconnected

  • This is often a sign of an incompatible version. Please make sure you are using a build correct for your system (e.g. 1.9, 2.0)

Other Errors

  • Console logs say Process finished with exit code 2
    • Cause: This indicates another instance of QZ Tray is already running on the designated ports on that machine. If it has become unresponsive, attempt to kill the QZ Tray's java process and try launching it again.
  • Error: typeerror: is not a function
    • Cause: Make sure the page is being rendered with UTF-8 <meta charset='utf-8'>.
  • Error: WebSocket connection to 'wss://localhost:8181/' failed: Error in connection establishment: net::ERR_CONNECTION_CLOSED
    • Cause: Java 9 (Beta) is known to cause this error. Please downgraded to a supported Java version.
  • Error: SCRIPT1010: Expected identifier qz-tray.js
    • Cause: IE11 may be emulating an older browser. Please use IE10, IE11 or Edge browser emulation. Offending code may look like this <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
  • Error: Server returned HTTP response code: 403 for URL
    • Cause: Assuming permission issues have been ruled out, some servers require a User Agent String to be passed to the web controller. QZ Tray 2.0 sends a blank User Agent String. QZ Tray 2.1+ provides a proper User Agent String. Alternately, disable the User Agent Filtering on the web controller. For example, Cloudfare callls this Browser Integrity Check and can be disabled.

Invalid JSON

  • If the browser console says Invalid JSON, try changing your HTTP headers in the sign-message example to use text/plain instead of application/json. In PHP, this is done via:

    - header('Content-Type: application/json');
    + header('Content-Type: text/plain');

    Note: This technique will vary depending on the server-side language being used.


  • Error: Automatic certificate installation is not available for this platform
    • Cause: Several.
      • Note: QZ Tray 2.1 uses Java for certificate installation and may correct this problem.
      • If using Comodo antivirus, use Advanced View, Auto-containment, Disabled before installing.
      • If using Windows XP, follow the on-screen instructions.
      • This issue may be caused by bad data being returned from certutil command. Contact for assistance.
  • Error: Can’t find script engine “VBScript” for script.
    • Note: QZ Tray 2.1 has removed the VBScript/JScript dependency and may correct this problem.
    • Cause: The Windows desktop installers for Windows use JScript engine for certain tasks. On occasion Antivirus Engines may try to replace this engine. To determine if this is the cause run the following commands from Command Prompt:
      reg query HKCR\CLSID\{cc5bbec3-db4a-4bed-828d-08d78ee3e1ed}\InprocServer32 /ve
      reg query HKCR\CLSID\{f414c260-6ac0-11cf-b6d1-00aa00bbbb58}\InprocServer32 /ve
      reg query HKCR\CLSID\{f414c261-6ac0-11cf-b6d1-00aa00bbbb58}\InprocServer32 /ve
      reg query HKCR\CLSID\{f414c262-6ac0-11cf-b6d1-00aa00bbbb58}\InprocServer32 /ve
    • If the system is configured properly, each command will return the following value:
      (Default)    REG_SZ    C:\Windows\System32\jscript.dll
    • If the system is misconfigured, it will return some other value. This value can be repaired by hand using the Windows Registry Editor.

Azure Fingerprint Setting
  1. Within the Azure web app, in the section Settings, TLS/SSL Settings, Private Key Certificates, Import
    • Upload the .pfx and type the password.
  2. Within the web app, in the Settings, Configuration, Application Settings, New Application Setting
  3. Adjust the code, replacing "<fingerprint>" with the certificate fingerprint.
    -	var KEY = "private-key.pfx";
    -	var PASS = "S3cur3P@ssw0rd";
    -	var cert = new X509Certificate2( KEY, PASS, X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.PersistKeySet | X509KeyStorageFlags.Exportable );
    +	X509Store certStore = new X509Store(StoreName.My, StoreLocation.CurrentUser);
    +	certStore.Open(OpenFlags.ReadOnly);
    +	X509Certificate2Collection certs= certStore.Certificates.Find(X509FindType.FindByThumbprint, "<fingerprint >", false);
    +	// Get the first cert with the fingerprint
    +	if (certs.Count > 0)
    +	{
    		X509Certificate2 cert = certs[0];
    		RSACryptoServiceProvider cspStrong = (RSACryptoServiceProvider)cert.PrivateKey;
    		byte[] data = new ASCIIEncoding().GetBytes(request);
    		byte[] hash = new SHA1Managed().ComputeHash(data);
    		Response.ContentType = "text/plain";
    		Response.Write(Convert.ToBase64String(cspStrong.SignHash(hash, CryptoConfig.MapNameToOID("SHA512"))));
    +      }

Cloudfront Cache Settings

  • In some instances, Amazon CloudFront will cache the query-strings sent to a signing controller. The symptom of this is intermittent popups as some signing requests will show "invalid" signature, others will show as valid.
  • To fix this, you will need to modify the CloudFront Cache Behavior:
    • Edit Cache Behavior, Cache Key Contents, Query Strings, Change from "None" to "All"

Keyset Does Not Exist

If the .NET signing example fails on a load balanced server, please try one of the following:

IIS User Profile Setting
  1. Change the setting which toggles the user profile for the application pool identity user. When set to false, the key containers aren't accessible:
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