You opened a tab and Safari flashed a little banner: “This webpage is using significant energy” — or, in newer versions, “This webpage is using significant memory.” It usually shows up in the address bar or as a note in the tab, and it feels alarming. The good news: it is a warning, not a failure. Your Mac is fine, and in most cases you can clear it in under a minute.
Here is what the message actually means, why one specific page triggers it, and the fixes in the order that works.
What the warning actually means
Safari watches how much power (energy) and RAM (memory) each open web page uses. When a single page keeps the CPU busy or holds onto a lot of memory — usually from JavaScript that never stops running, a video or animation loop, or a memory leak in the site itself — Safari flags it so you can act before it drains your battery or slows the whole browser down.
- “Significant energy” = that page is keeping the processor working hard, which heats the Mac and eats battery. Common on pages with autoplaying video, live dashboards, crypto/ad scripts, or a game.
- “Significant memory” = that page is holding a large amount of RAM. Common on huge documents (Google Docs/Sheets with hundreds of rows), web apps left open for days, or sites with a memory leak.
Key point: the warning is about one web page, not your Mac. It is Safari being helpful — not a virus, and not a sign your Mac is dying.
The fixes, fastest first
1. Reload the tab
The single most effective fix. A reload throws away whatever runaway script or leaked memory the page built up and starts it clean. Press Cmd + R (or Cmd + Shift + R for a hard reload). Nine times out of ten the banner is gone.
2. Close the tab you are not using
If the flagged page is one you do not need open right now — a background dashboard, a video you paused, a doc you finished — just close it. Web apps you leave open for days (email, chat, spreadsheets) are the usual memory hogs.
3. Find the real culprit in Activity Monitor
Not sure which tab is the problem? Open Activity Monitor (Applications ▸ Utilities), click the Energy or Memory tab, and look for entries that read Safari (the site name) or Safari Web Content near the top. Safari lists each heavy tab as its own process, so you can see exactly which page to close. Related: our full guide to freeing up RAM and fixing memory pressure on a Mac.
4. Turn off (or update) the extension doing it
Ad-blockers, coupon finders, and script injectors run on every page and are a top cause of runaway energy use. In Safari ▸ Settings ▸ Extensions, turn them off one at a time and reload the page. If the warning disappears, that extension was the culprit — update it or leave it off.
5. Pause autoplaying video and animations
A single autoplaying 4K video or an animated ad can trip the energy warning by itself. Mute or pause it, or right-click the tab and choose Mute Tab. You can stop most sites from autoplaying in Safari ▸ Settings ▸ Websites ▸ Auto-Play.
6. Quit and reopen Safari
If several tabs are flagged at once, Safari itself may have accumulated memory over a long session. Quit Safari completely (Cmd + Q) and reopen it. Turn on Safari ▸ Settings ▸ General ▸ “Safari opens with: All windows from last session” first so you do not lose your tabs.
7. Update macOS and Safari
Older Safari versions leak memory that newer ones fixed. Go to System Settings ▸ General ▸ Software Update and install anything pending, then restart.
When it is not the web page — it is the Mac
If the energy or memory warning shows up on ordinary pages — a plain news article, your email — and reloading does nothing, the bottleneck may be your Mac, not the site. That is especially common on 8GB Macs where every heavy tab pushes the system into swap.
Two honest tells:
- The warning appears constantly, on light pages, right after you open Safari.
- Everything else is sluggish too — see our guides on Safari being slow or pages not loading and a MacBook running slow in general.
If your Mac is an Intel model or an 8GB machine that already feels tight, more browser tabs will not stop tripping these warnings — the RAM ceiling is real, and you cannot upgrade memory on an Apple-silicon Mac after purchase. At that point a newer, faster Mac is the actual fix. A clean refurbished M2 MacBook Air is $974.99 and an M1 Pro MacBook Pro is $899.99 at LuxuriousComputers — both handle dozens of heavy tabs without breaking a sweat. Browse the current Apple clearance deals if budget is the deciding factor.
Frequently Asked Questions
Is “this webpage is using significant energy” a virus?
No. It is a normal Safari warning that one web page is using a lot of power or memory. It is not malware and does not mean your Mac is infected. Reload or close that tab and it clears.
Why does one specific website keep triggering it?
That site runs heavy JavaScript, autoplaying media, or has a memory leak that grows the longer the tab stays open. Reloading resets it; if it comes back within minutes, the site itself is the cause — not your Mac.
Does the warning hurt my Mac or battery?
The warning itself does nothing. The page it is flagging does drain battery faster and can warm the Mac. Closing or reloading that tab restores normal battery life immediately.
Will more RAM stop these warnings?
On a memory-pressed Mac, yes — a machine with more RAM absorbs heavy tabs far better. But you cannot add RAM to an Apple-silicon MacBook after buying it, so the practical move is a Mac with more memory to begin with. See the upgrade options above.
How do I find which tab is the problem?
Open Activity Monitor, click the Energy or Memory tab, and look for the top “Safari Web Content” entries — each heavy tab is listed separately, often with the site name, so you can close the exact one.