The Sauce Labs Cookbook

Sauce Headless

Front End Performance Testing


External Resources

More Info

Page tree
Skip to end of metadata
Go to start of metadata

Seeing a Security Error Message (Error #2048)

This error is displayed when the ports used by manual testing relies are being blocked by a firewall on your end. This may also be caused by running applications such as Avast! antivirus software.

These are the servers and ports used by manual testing. Please check with your IT organization that they are accessible.

If you are launching manual testing from Internet Explorer on your local machine:


If you are launching manual testing from any other locally-installed browser:


We recommend making all of these accessible if you plan on using several browsers locally.

Seeing a Black Screen / "Plugin Failure" Error

If your test shows a black screen after starting the virtual machine, you may need to reinstall Adobe Flash Player on your machine. This should only occur if you are using Internet Explorer to launch Sauce Manual Testing, which requires this software for our in-browser VNC player to function.

Long Load Times or Timing Out

We've streamlined our service to provide the best possible load times. If you are seeing slow manual testing sessions, check our status page, or get instant updates by following @sauceops on Twitter.

All Links Open in New Tabs

It's possible for the manual testing VNC client to have a modifier key "stuck" down, causing any clicked links to open in new tabs. This happens if the client loses focus while a key is held down -- for example, when using Alt-Tab to switch application windows. In this case, VNC never receives the keyUp event.

To prevent this from happening: every time you focus back on the manual testing window, first click in the middle of the page, then press and release all the modifier keys (like Alt, Control, Command, and Shift).

Job Does Not Load

There are two common scenarios here:
  • Error message: "Uh oh! Some error occurred while connecting to the browser"
  • The job seems to start, but you see only a white text box in the middle of a black screen.
Both of these indicate that your browser is having trouble displaying the VNC stream from the remote machine. Take the following steps to troubleshoot:
  • Check the video on Sauce: If the recorded video after the job shows a steady video stream, this indicates that the issue is in your computer or connection to Sauce. However, if the Sauce video shows the same issue, that indicates an issue in our service. In that case, send us the URL for the job page and a screenshot of the issue.
  • Check that your browser is up to date: If you're on an older version, this may cause incompatibilities. Update your browser and try again.
  • Check your firewall: make sure that your machine allows full access for the interactive stream over the required ports.
  • Check that the Internet connection is stable: We recommend running Sauce tests from a machine with a wired Ethernet connection, to ensure a steady connection. If the connection flickers, this error could be thrown.

Want more?

If you'd like to dig deeper, feel free to check out our help forums or email us directly at