How to Fix: A website is slowing your browser in Firefox?

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 bring the browser back to its normal state.

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

If I hit the Wait button, then 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 simply stated that “A website” is slowing the browser, it doesn’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 Forum and are looking for ways to fix this issue.

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

Use Firefox’s Strict Protection

In many instances, this issue arises when there are problems with the page’s script file. This when combined with the browser’s trackers only makes the matter worse. So the best bet is to disable these trackers and allow the scripts to load efficiently.

  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 your browser and check if the page is able to load correctly or not.

While this solution has been known to work for some, however, there’s a counter-argument to it. Enabling the Strict mode could itself break some site components, which would only degrade the current issue. So if this happens with you as well, then 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 in identifying the culprit, however, the Firefox Task Manager could help you out a little bit. It lists out all the sites along with the total resources that they are consuming. You may then have a look at the same and close the site that leads to the maximum consumption.

Here are the steps to use Firefox Task Manager to quit website tabs:

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

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

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

Delete Firefox Data

As you keep on using the browser, its data gets accumulated over the due course of time. This would slow down the entire 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 Firefox data:

  1. Launch Firefox Computer browser.
  2. Access about:preferences#privacy in address bar to open 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 checkbox.
  5. Hit on the Clear button.
    Clear Data window in Firefox browser

Check if it is able to fix the A website is slowing your browser 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 the one-time compromise 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 present 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 Adobe Flash protected mode:

  1. Go to your Desktop screen, 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 fine, and type in ProtectedMode=0 and then save it.
  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

If you are still dependent on Flash contents, then this file might prevent it from loading. So either tweak the ProtectedMode value to 1 or delete the file altogether.

Refresh Firefox’s Processes

For the proper running of this browser, all its related frameworks, processes, and services need to be up and running as well. If there’s an issue with any one of them, then the entire browser might suffer.

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

Here are the steps to refresh the Firefox process:

  1. Launch Firefox Computer.
  2. Open about:config page in the browser address bar.
  3. Click on Accept the Risk and Continue command button to proceed with caution.
    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 as well.
    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 would now have been fixed.

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

Bottom Line: Firefox Website Slowing Browser

So this was all from this guide on how you could fix the A website 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 properly. Upon switching over to the Strict Protection mode, the issue got resolved.

Do let us know in the comments which one spelled out success for you.

Lastly, here are the recommended web browsers for your computer and mobile phone that you should give a try.

WindowsMacOSiOSAndroidLinux
Chrome WindowsChrome MacChrome iOSChrome AndroidFirefox Linux
Firefox WindowsSafari MacSafari iOSEdge AndroidChrome Linux
Edge WindowsFirefox MacEdge iOSSamsung InternetEdge Linux

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