@elmiraberjisian ,  You almost certainly have either figured out an answer to your question above or found a work-around. This question in the Qualtrics system is quite old! But since you never got anyone to reply to your question, I thought I would give it a try.

If you're experiencing issues with videos playing correctly in Firefox but working fine in other browsers like Google Chrome and Safari, it is most likely due to compatibility or codec-related issues. Here are a few suggestions to help you troubleshoot and potentially resolve the problem:

1. Check video format and codec: Make sure the videos you're using are in a compatible format and codec for playback in Firefox. Generally, videos in MP4 format with the H.264 codec tend to have better compatibility across browsers. If your videos are in a different format or codec, consider converting them using a video converter tool to the recommended format.

2. Update Firefox: Ensure that you're using the latest version of Firefox, as updates often include bug fixes and improvements to video playback. Go to the Firefox menu, click on "Help," and then select "About Firefox" to check for updates.

3. Clear cache and cookies: Sometimes, issues can arise due to cached data or corrupted cookies. Clear your browser's cache and cookies to eliminate any potential conflicts. In Firefox, you can do this by going to the menu, selecting "Options," then "Privacy & Security," and under the "Cookies and Site Data" section, click on "Clear Data."

4. Disable browser extensions: Certain browser extensions or add-ons can interfere with video playback. Temporarily disable any extensions you have installed and test if the issue persists. If the videos play correctly without the extensions enabled, you can try re-enabling them one by one to identify the specific extension causing the problem.

5. Try using a different video player: Instead of relying on the default video player embedded in Qualtrics, you can experiment with using an external video player for Firefox. For example, you can use HTML5 video tags with a specific player library like Plyr.js or Video.js. These players often provide better cross-browser compatibility and more advanced features.

6. Contact Qualtrics support: If the issue persists, reach out to Qualtrics support for further assistance. They may be able to provide specific guidance or insights into any known compatibility issues with Firefox.

Remember that troubleshooting technical issues may require some trial and error. It's also a good idea to test your survey on different devices and browsers to ensure optimal compatibility and a consistent experience for all respondents. Have you ever tried BrowserStack? That is one program I like alot for troubleshooting.