This section gives a few tips for how to troubleshoot common errors in Labvanced. Remember that these are only suggestions and not all questions are answered here.

If you come across a major issue with your study or the Labvanced platform, please contact us right away to schedule a support call.

General Implementation Issues

I made a small adjustment and I don't like it, but I don't remember how it was before. Is there a way to undo the change?

Yes, pressing Ctrl and Z at the same time will undo the last change made.

My experiment doesn't behave as I want to, but I cannot figure out why. What can I do?

Please refer to the corresponding text and video documentation for information. You could also try looking through the experiment library to find a study that is similar to your design and check for differences in event logic. If you don't get any further, please contact us via the live chat.

I don’t find a suitable example/template study. Can Labvanced provide me with a customized template/prototype for my study?

We always provide a highly customized prototype for users holding a premium or a lab license. However, we also try to provide our best support to all users. Please contact us and tell us what you need using our chat support. We will help you as much as we can!

I am stuck with my experiment implementation, can Labvanced help me with this?

Yes. We want each user of the Labvanced platform to be able to create their experiment as fast as possible without problems. Tell us about your current problem and what you are trying to achieve using our chat support.

I think found a bug, where can I report it?

Bugs happen in any software project. We appreciate every bug report and we will start to fix is as soon as possible. Please use either our contact form or the live chat to report the bug.

What is the easiest way to get in touch with people from Labvanced if my question is not listed here?

Please use the live chat (the green icon on the lower right).

Tasks and Trials

My study / task doesn't open. What can I do, can Labvanced fix this?

Yes we can fix this, so don't worry! This usually happens when something was deleted (often a variable or factor) which is still used somewhere in the experimental logic. Please contact us via the live chat, telling us the name of your study. For more advanced users, you can open the developer tab (in Google Chrome: the three dots on the upper right-->more tools--> developer tools-->console). If you see a red error message, you can also send that information to us, this way we can fix your problems faster.

I seem to be missing a task in my experiment. How can this be resolved?

Check and make sure that you have added the task to the Blocks list. If a task has not been assigned to a Block, the experiment will run without it. The same goes for assigning Blocks to Sessions and Sessions to Groups. Ensure the flow of the experiment in the Editor is correct and all items are accounted for.

My trials are appearing in the wrong order. Why is this happening?

The default order of trials is randomized. Be sure you have accessed the Randomization menu in the Task Editor and have adjusted the settings to your desired configuration. Also, allow enough time for your stimuli to load after you have imported them to the experiment.

When I run the study, the frames are blank. Why is this?

This issue could be more complicated. As a first step, make sure you have properly added your stimuli to objects and assigned them to trials. Then, add a text object to all frames that contain a variable. In the text box, use the text editor to add a variable to the box. Then, run the experiment again. This will show you what variables are being executed and which values they are printing.

If the text boxes show up blank, this means a variable is not being recorded properly and is probably why the study is not running correctly. On all the frames where the "missing" variable is used, look for the 3 checkboxes under the description of the variable in the Variables tab. Often the reason is that the box "reset at trial start" is checked when it should not be. Uncheck the box and do a test run again.

If this does not solve the issue, reach out to us via the live chat.

Some videos are playing during my study, but other videos are not. Why is this?

Make sure all videos are in .mp4 format and adhere to our guidelines. Sometimes the issue is with the video link itself, not Labvanced, so try removing all videos from your study and re-uploading them. Often the video is missing some metadata or the encoding is broken.

If you can, try accessing the Developer Tools in Google Chrome to see if there is a specific issue that you can send to us.

If you have copied the video link from your browser into Labvanced, you need to change the URL from "watch" to "embed." For example, here is the original URL copied from YouTube: and here is the URL that should be written in the Object Properties of the iFrame:

My images are loading very slowly, sometimes such that only parts of the image load at a time.

There could be a few reasons for this. Please check each of these points:

  • Try reducing the file size or making the image smaller
  • Make sure preloading of media is enabled in the Study Settings tab
  • Put images into .jpeg format
  • Use this website to check your internet speed: Check Internet Speedopen in new window
    • If the download and/or upload value is below 20 mbps, your internet is not strong/fast enough to load your stimuli. Try connecting to a different network.

If after trying each option, your images still do not load, let us know via the Live Chat.


When I check the data output, it looks like some of the variables did not record any data. How can I fix this?

Go back into the task where those variables are located. Check to see that the variable type (in the Variables tab) matches the type of data that is intended to be stored in that variable.

Next, check the Events tab and confirm that there is a correctly structured event to record that variable. Look carefully in the Set/Record variable action to ensure there are no options left blank or incomplete.

If these strategies do not reveal any obvious errors, try creating a new version of the variable and redo the setup carefully, referring to the Guide and the Study Creation Questions for specific variable information.

Running Studies

Editing the experiment works fine. However, when I start/run the experiment there is a problem. What can I do?

There could be different reasons for this. Many times there is a missing or wrong reference to an object or to a variable in one or more events. Make sure that all variable names are unique, because this is another common reason for errors. Also, check the event logic thoroughly, as logic mistakes happen often with more complex events. If these suggestions don't help, please contact us via the live chat.

My experiment keeps freezing/going to a blank screen/etc. How can I fix this?

Check that all variables are linked properly, variables that should remain constant are not being reset at trial start, and no variables that should be in use have been deleted. Save the study and reload the page. Then, go to the Events and ensure that the logic is correct.

If the variables and events are correct, follow these steps to let us know about the issue:

  • Press F12 (in Chrome and Firefox). You may need to press fn + F12 or another f-lock button simultaneously.



  • Open Developer Tools and open the console.
  • Screenshot the latest entry in the console or any red error text that you see.

console error

  • Email us the screenshot along with your username, the name of the study, and the task in which the error occurred.

I received an Error 957. How do I fix this?

There are 2 factors at play in this error. First, try replacing any files used in your experiment. If that doesn't fix the error, go to the Study Settings tab and change the settings for "On resource upload error" from "abort" to "continue." If there is still an error, please contact us.

I performed a Test Run and received an error message of "you do not have access to the experiment."

Check to make sure the experiment is not being shared or published. Make sure your browser is one of the ones accepted by your experiment, hit Save, and refresh the page.

I want to test run my study, but I keep seeing the same trial every time. Why is this?

If your task involves a random factor that is balanced between subjects, you must test the study as a participant with a recording session. This is because the test run alone will not simulate the randomization correctly, as the subject counter is not increasing unless data is being recorded. There is no need to fully publish the study, simply enable a recording session and test it in the Run tab.

My participants are not being assigned to Groups in the order that I want. How can I edit this?

In the Study Settings tab, under Main Settings, there is an option to assign participants to Groups based on the subject counter. Subjects will automatically be assigned to the group with the lowest subject count. You can choose to increase the count when a subject joins the study (which ensures balancing, but could lead to incomplete datasets if a subject quits early) or when a subject completes the study (ensures complete datasets but could lead to unbalanced groups if multiple subjects start at one time).

If you notice one Group has more participants than another Group, review the settings in the Study Settings tab and consider changing the subject counter option. Also check to make sure that your Groups are properly set up in the Study Design tab.

Using iOS, Cellphones, and Tablets

My study has videos that are not playing on a device running iOS. How can I fix this?

Devices running iOS are unable to autoplay videos due to security features. Therefore, if your study has videos that start to play without a directly preceding participant interaction (i.e. mouse click or keyboard press), the study will not be able to play them on iOS devices.

However, there are workarounds for this. If the previous frame ended with a user action, like a mouse click, then the video can be started on the next frame. Here is a sample study that outlines these options: Media Autoplay on iOSopen in new window

Are there certain functions that are not compatible with iOS devices?

This question is constantly being updated as we receive feedback from our users. Currently, these features are known to be problematic on devices running iOS:

  • Video Object (see instructions above)
  • Audio Object (see instructions above)
  • Input Object: calendar date as the required answer

My participants cannot respond to a stimulus in my study. Why is this?

If your study involves key presses as decisions/responses, this feature is very difficult for cellphones and tablets. Often, the keyboard will not appear unless there is an input response object. To make your studies suitable for all devices, try either a text input object and an event to read the response, or use buttons instead of key presses. Always test run your study on all the devices that you plan to allow to ensure smooth execution.

Eyetracking Troubleshooting

My experiment is not loading the eyetracking program. What can I do to fix this?

There are several ways to ensure that eyetracking works smoothly in your study. Try these tips:

  • Check your task manager on your computer and make sure there are no background processes that are consuming a lot of CPU or RAM.
  • Close all other applications, browser tabs, and windows. This frees up some processing power.
  • If you are using a laptop, plug it into a power socket.
  • Set your computer to "performance" in the Windows power management settings.
  • Use a computer with a real graphics card, if possible.
  • Switch your browser to Chrome.
  • Use Windows as your operating system.
  • Update all of your device drivers.

It is good practice to tell your participants to close all other tabs before beginning an eyetracking study to prevent loading errors or studies that are loading too slowly to be accurate.

How can I make sure that I am getting the best eyetracking data?

In addition to the tips listed above, here are some general tips for structuring a good environment for eyetracking:

  • Ask participants to remove eyeglasses or face coverings.
  • Make sure your eyes are clearly visible in the webcam.
  • Lighting conditions should be constant, but not behind the subject or too strong.
  • Make sure the webcam is very near to the monitor, if not attached to it. This helps set the center pose accurately and ensures the full face is being captured.


I think found a bug, where can I report it?

Bugs happen in any software project. We appreciate every bug report and we will start to fix is as soon as possible. Please use either our contact form or the live chat to report the bug.

What is the easiest way to get in touch with people from Labvanced if my question is not listed here?

Please use the live chat (the green icon on the lower right).