This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

JavaScript Performance Issues

  • 4 replies
  • 2 have this problem
  • 10 views
  • Last reply by DudeMan101

more options

I am having extreme JavaScript performance issues. The one website that I routinely visit takes roughly 30s to load. During this time Firefox hangs and you can't use any other tab. The site in question loads instantly in Chrome while not affecting other tabs. The tab related issue would be do to Chrome loading tabs in separate processes, but the JavaScript issue is not tab related.

I have another site I visit often that loads and performs extremely poorly, but not as bad as 30s load time. I am running stable, not nightly. The site(s) in question are adult related, so I don't want to post the URL's without permission as I'm not sure I would be allowed to post the URL's.

This issue alone forces me to use Chrome as I can't be waiting 30s for a website to load.

Some other key notes: - While loading the site in question, Firefox uses 25% CPU (maximizing 1 core) - While loading the site in question, Firefox uses > 1.3 GB in RAM... drops to 300 MB after site has loaded - I have created a fresh profile and a fresh Firefox installation and the problem still persists

I am having extreme JavaScript performance issues. The one website that I routinely visit takes roughly 30s to load. During this time Firefox hangs and you can't use any other tab. The site in question loads instantly in Chrome while not affecting other tabs. The tab related issue would be do to Chrome loading tabs in separate processes, but the JavaScript issue is not tab related. I have another site I visit often that loads and performs extremely poorly, but not as bad as 30s load time. I am running stable, not nightly. The site(s) in question are adult related, so I don't want to post the URL's without permission as I'm not sure I would be allowed to post the URL's. This issue alone forces me to use Chrome as I can't be waiting 30s for a website to load. Some other key notes: - While loading the site in question, Firefox uses 25% CPU (maximizing 1 core) - While loading the site in question, Firefox uses > 1.3 GB in RAM... drops to 300 MB after site has loaded - I have created a fresh profile and a fresh Firefox installation and the problem still persists

All Replies (4)

more options

A website taking a long time to load doesn't necessarily mean that you are having JS issues.

Let's get some of the basic groundwork out of the way:

If this helps, please let us know. If not, again, please let us know and we can continue to chase this down

more options

Sorry, I should have mentioned in the first post they are JavaScript heavy websites. While not necessarily meaning it's a JS issue, the odds are quite high it is.

As for the groundwork:

  • I'm currently running 32.0.3, running on the latest version of stable. I have tried a fresh install of 32.0.3 as well, completely uninstalling and removing my profile. Currently back to running my old profile.
  • No malware, I have my system protected and also have scans daily.
  • Currently using the latest drivers for my graphics card. I already had hardware acceleration and WebGL turned on in Firefox, but I tried disabling and got the same results. The page still took roughly 30s to load, so I went back and enabled both those options again.
more options

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

  • Hold down the Shift key and left-click the Reload button
  • Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
  • Press "Command + Shift + R" (Mac)

Clear the cache and remove cookies only from websites that cause problems.

"Clear the Cache":

  • Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

  • Firefox/Tools > Options > Privacy > "Use custom settings for history" > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

  • Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
  • Do NOT click the Reset button on the Safe Mode start window
more options

The cache was already cleared. I already have done a complete fresh install, which means there was nothing in the cache to begin with. Suffice to say, after doing a clear cache just now, it did not work.

Same deal with Safe Mode. The fresh install means there were no extensions, add-ons, etc. Using Safe Mode just now did not work.