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Fix: A web page is slowing your browser error in Firefox on the Computer

Are you encountering the "A Website is Slowing your Browser" alert in Firefox? Discover how to address and resolve this issue on your computer.

The Firefox alert saying ‘A website is slowing your browser’ is generally due to heavy processes running in the background.

We can check the task manager to identify and stop the process to return the browser to its normal state.

You can also remove the heavy add-ons, clear cache data, and refresh the Firefox processes to resolve errors.

Fix: A website is slowing your browser error in Firefox

Recently while visiting a website via Firefox, I was greeted with a popup message that said, ‘A website is slowing your browser’. Alongside that, there were two options: Stop it and Wait.

If I hit the Wait button, I again got this error within a few seconds. On the other hand, the Stop button would prevent the site from loading any further.

A Page is slowing down your browser alert in Firefox

To make the matter worse, the error message stated that ‘A website is slowing the browser’; it didn’t mention the actual site that was the root cause.

In this regard, many concerned users have already voiced their concerns across various Mozilla Support Forums and are looking for ways to fix this issue.

If you are also on the same page, this guide is here to help you. Follow along for the various workarounds.

Use Firefox’s Strict Protection

This issue often arises when problems with the page’s script file exist. When combined with the browser’s trackers, this only worsens the matter. So the best bet is to disable these trackers and allow the scripts to load efficiently.

Here are the steps to use Firefox’s Strict Protection:

  1. Launch the Firefox browser and head over to the below location:
    about:preferences#privacy
  2. Select Strict under Enhanced Tracking Protection.
    Firefox Enhanced Tracking Protection Strict Mode
  3. Restart the browser and check if the page can load correctly or not.

While this solution has been known to work for some, there’s a counter-argument to it. Enabling the Strict mode could break some site components, which would only degrade the current issue. So if this also happens with you, switch back to the Standard Mode and move over to our next fix.

Using Firefox’s Task Manager

While the error message doesn’t help identify the culprit, the Firefox Task Manager could help you a little.

It lists all the sites and the total resources they are consuming. You may then look at the same and close the site that leads to the maximum consumption.

Here are the steps to use Firefox Task Manager:

  1. Launch Mozilla Firefox on the computer,
  2. Type in about:performance in its address bar, and hit Enter key.
    This will bring up all the currently open sites and their impact on memory.
    Kill High Memory Processing Tab in Firefox Window
  3. Hover your mouse to the one with the maximum energy impact, and hit the Close X button.

This will close that site, and hopefully, the issue will be fixed.

Sometimes, the site exhausting the maximum resource might not be the culprit. So you would have to turn your attention to the second or third most energy-impact websites and act accordingly.

Delete Browsing Data

As you keep on using the browser, its data gets accumulated over the due course of time. This would slow the browsing experience, and the sites’ loading time could be among the biggest suffering parties. So it’s recommended to delete these cache and data files right away.

Here are the steps to clear data:

  1. Launch the Firefox browser on the computer.
  2. Access about:preferences#privacy in the address bar to open the Privacy and Security section.
  3. Scroll to the Cookies and Site Data, and click on Clear Data.
    Firefox Clear Data command button
  4. Select both the Cookies and Site Data and Cached Web Contents checkboxes.
  5. Hit on the Clear button.
    Clear Data window in Firefox browser

Check if it can fix the error in Firefox. Deleting cache and data would log you out of sites, and the latter might take a few more seconds the next time it loads.

However, these are just one-time compromises that could prove worthy of the efforts.

Disable Adobe Flash’s Protected Mode

Adobe Flash has now been depreciated for HTML5. However, some of its components are still in most modern web browsers.

One such functionality is Flash Player’s Protected Mode. Since it is no longer being used in Firefox, it’s better to disable it. Otherwise, its scripts could slow down the entire loading time of websites. Here are the steps to disable it:

  1. Go to your Desktop screen, and right-click on an empty location for the context menu.
  2. Select New > Text Document from the menu.
    Create New Text Document in Windows
  3. Name this file as mms.cfg (make sure you change the extension type from .txt to .cfg).
  4. Open the file and type in ProtectedMode=0 code, and save.
  5. Now launch File Explorer and go to the following location:
    C:\Windows\SysWOW64\Macromed\Flash

    Macromeda Flash mms.cfg file in windows

  6. Copy-paste the mms.cfg file within this Flash directory.
  7. It might request for administrative permission dialog box, click Continue command button.
    Continue to Access the System Folder in Windows

This file might prevent loading if you are still dependent on Flash content. So either tweak the ProtectedMode value to 1 or delete the file.

Refresh Browser Processes

For the proper running of this browser, all its related frameworks, processes, and services must be up and running. The entire browser might suffer if there’s an issue with any of them.

As far as the current issue is concerned, the HangMonitor and ProcessHangs are the two responsible processes. So restarting both these processes might fix the underlying issue.

Here are the steps to refresh the Firefox process:

  1. Launch the Firefox app on the Computer.
  2. Open about:config page in the browser address bar.
  3. Click on Accept the Risk and Continue command button to proceed cautiously.
    Firefox Proceed with Caution
  4. Now type in dom.ipc.processHangMonitor in the search box, and hit Enter key.
  5. Click on the toggle button firefox-javascript-toggle situated at the extreme right to change its value to False.
    dom.ipc.processHangMonitor Firefox Config
  6. Likewise, search the dom.ipc.reportProcessHangs and change its value to False.
    dom.ipc.reportProcessHanges Flash Config
  7. Wait for a few seconds, and revert the value of both these processes to True.
  8. Restart your browser once, and the issue will now have been fixed.

While this process does have a few technicalities involved, upon successful execution, the issue might be rectified.

Bottom Line

So this was all from this guide on how to fix the ‘A web page is slowing your browser’ error in Firefox. We have shared five different types of fixes, any one of which should work out for you.

In my case, the trackers weren’t allowing some website components to load correctly. Upon switching over to the Strict Protection mode, the issue got resolved.

Please let us know in the comments which spelled out success for you. Or if you’ve tried anything else that has worked to fix the Firefox slow browser.

Lastly, if you've any thoughts or feedback, then feel free to drop in below comment box. You can also report the outdated information.

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Kushal Azza

Kushal Azza

Kushal Azza is a Google Certified IT Professional, Digital Content Creator, and Go-To Digital Marketer with Engineering Degree. He has over a decade of experience solving tech problems, troubleshooting, and innovating digital solutions. Follow him on Twitter and LinkedIn.

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