This Webpage Is Using Significant Memory/Energy on Safari, What to Do?

Many Safari-users found that when using Safari on a Mac, "This webpage is using significant memory (or energy). Closing it may improve the responsiveness of your Mac" will suddenly pop up. Some users also reported that this message appeared when they tried to use Safari to open Netflix, Facebook, and websites such as CNN, CBS, MSN and so on. Many a user also encountered the same error when using another browser, Firefox.

Why Does Safari Keep Saying: This webpage is using significant memory (energy)?

Currently, there is no clear reason to explain why this error occurred. But it's related to the update of macOS High Sierra for the problem only came out after users have upgraded the system to macOS High Sierra on their MacBook. The problem hasn't been seen on macOS Sierra, OS X El Capitan or earlier.

In this regard, here are six easy ways for you to figure out how to fix "This webpage is using significant memory(energy）" on Safari.

1. Force Quit Safari

It's a simple way to quit Safari. Open Apple icon, then click Force Quit Application. After that, choose Safari in the app window. At last, click Force Quit button to quit.

2. Turn off Extensions on Safari

If you want to figure out why the error "this webpage is using significant memory/energy" pops up, turning off Safari Extensions is the way to go.

Step 1. Choose Preference from the Safari menu.
Step 2. Select the Extensions icon, then you'll see many extensions from the list. Choose one extension.
Step 3. To turn off that extension, deselect the Enable checkbox.
Step 4. Now, it's time to see whether if the "significant memory/energy" error comes back after turning off an extension. If the answer is yes, clicking Updates to update the extension or you can delete the extension by clicking the Uninstall button.

3. Delete Internet Plug-ins from Safari

Internet plug-ins and other add-ons can also be the reasons why Safari is acting weirdly. So deleting unused plug-ins may help to fix the report of the webpage with significant memory.

Step 1：Quit Safari and Open Library folders

Open Go > Go to Folder from the menu bar. Then type /Library and click Go to open the Library folder.

Step 2: Remove Files from Library Folders

The following Library folders contain files for Safari add-ons. Move the listed files in these folders to the Trash：

• Internet Plug-Ins (Keep in mind that do not remove these files: Default Browser.plugin, nslQTScriptablePlugin.xpt, Quartz Composer.webplugin, or QuickTime Plugin.plugin.)
• Input Methods
• InputManagers
• ScriptingAdditions

Step 3: Put the Files Back to Library Folders

See whether removing the files from these folders resolves the issue. If it works out, quit Safari again. Then gradually put the files back to Library folders until you find the file that is causing the problem.

4. Clear Safari History, Cookies and Cache

At the very beginning, I would like to explain what are cookies. Cookies are files on your Mac which help to keep the information of what you've done on a website. To remove history and cache of Safari, there is a useful app for you to clear cookies, history on Safari at once: FonePaw MacMaster, which can remove data that you don't need completely. The following steps below are to help clear Safari's history and cache on Safari.

Step 1. Download and install FonePaw MacMaster on Mac.
Mac Version Download
Step 2. Select Privacy option.
Step 3. Click Scan. Wait until scanning is done, choose Safari. Tick Cookies, Search History and more, click Clean button so as to clear Safari history.

5. Switch to Google Chrome For Help

If the problem has not been resolved, you can use Google Chrome to replace Safari. The message "this webpage is using significant memory or energy" haven't been found on Google Chrome.

6. Update or Downgrade macOS

The error appears only after upgrading to macOS High Sierra. So you can try upgrading your MacBook or iMac to the latest macOS Mojave version or downgrading High Sierra to an earlier version.

Above is the full guide to figure out how to fix "This webpage is using significant memory(energy）" on Safari.