Why Is Safari So Slow on Mac? (And How to Speed It Up)

Safari should be the fastest browser on a Mac. WebKit is highly optimised for Apple Silicon. Battery life is better than Chrome by a meaningful margin. So when Safari feels slow, something specific has gone wrong — and it’s almost always one of about six things.

Here’s how to figure out which one is biting you.

Quick test: is it Safari or your Mac?

Open Activity Monitor (cmd-space → Activity Monitor → return). Memory tab. Look at Memory Pressure at the bottom.

If pressure is yellow or red, the issue isn’t Safari — it’s overall RAM. Every app feels slow when memory is full. Quit other apps, restart heavy ones (Slack, Teams, Discord), and Safari will likely recover.

If pressure is green but Safari is slow, then it’s Safari-specific. Read on.

Suspect 1: Too many tabs

The single most common cause. Each Safari tab is a process or shares one with related tabs. Twenty active tabs eating CPU and memory will make the address bar laggy when you type.

Especially heavy:

• Tabs with autoplay video (YouTube, Twitter, news sites)
• Slack web, Trello, Asana — anything with constant network polling
• Old tabs you haven’t touched but that are still running JavaScript
• Sites with infinite-scroll feeds left scrolled deep

Close tabs you don’t actively need. Use Tab Groups (Window → Tab Groups → Save current tabs as group) to stash them for later without keeping them live.

After closing, watch Activity Monitor. You’ll see “Safari Web Content” processes drop and Safari snap back to fast.

Suspect 2: Misbehaving extension

Open Window → Activity in Safari (cmd-option-A). It shows CPU per page. If you see a number jumping while you’re not interacting with anything, an extension is doing it.

Disable extensions: Safari → Settings → Extensions. Uncheck them all. Reload pages. If Safari’s now fast, re-enable one at a time to find the culprit.

Common offenders:

• Old ad blockers with massive filter lists
• Reader-mode extensions (Safari has Reader built in)
• Tools that watch every page (price trackers, “improve this site” extensions)
• Translation extensions that auto-detect on every load

You can usually drop two or three extensions and never notice their absence.

Suspect 3: A specific website is the problem

One bad tab can drag the whole browser. Window → Activity in Safari shows per-page CPU. Find the page chewing 80%+ CPU and either close it or reload it.

Some sites are known to be heavy:

• Twitter/X with a busy feed
• LinkedIn (feed plus all the social pings)
• News sites with autoplay video and tracking scripts
• Old web apps that have memory leaks

Close that one tab and see if Safari recovers.

Suspect 4: Stale or corrupted cache

A bloated Safari cache can make individual sites slow. Clear it without losing your sign-ins:

1. Safari → Settings → Advanced
2. Tick “Show features for web developers”
3. Now there’s a Develop menu — click Develop → Empty Caches (or cmd-option-E)

Cookies and history stay. Cache is gone. Sites fetch fresh resources on next load.

For one specific site: Safari → Settings → Privacy → Manage Website Data → search the site → Remove. More targeted than nuking everything.

Clear caches across every browser at onceSweep clears Safari, Chrome, Firefox, and Arc caches in a single pass. Free download for Mac →

Suspect 5: Outdated Safari (and macOS)

Safari is part of macOS. To get a current Safari, you need to be on a current macOS. If you’re on macOS Sonoma 14.0 (released 2023) and never updated, you’re missing dozens of WebKit improvements.

System Settings → General → Software Update. If a major version (Sequoia 15) or point release is waiting, take it.

Each macOS release includes meaningful Safari improvements. The performance gap between an outdated and current Safari is real.

Suspect 6: System-level slowdown

Safari is fast in isolation. If your Mac itself is slow, Safari can’t escape that.

Check:

• Storage — Apple menu → About This Mac → More Info → Storage. Below 15% free? Free up space.
• Spotlight — mds_stores or mdworker_shared at the top of Activity Monitor → CPU? Indexing is hammering your disk. Wait it out or rebuild the index.
• Photos — photoanalysisd busy? Photos is doing background analysis. Plug into power so it finishes faster.
• Background syncs — iCloud Drive (bird), Dropbox, Google Drive, OneDrive all syncing at once? Pause them for now.

A system that’s busy in the background can’t give Safari the resources it needs.

Less common: Safari’s privacy database is huge

Safari maintains a database of trackers and known bad domains for its tracking-prevention features. After a year of heavy use, this database can be 100+ MB and slow down navigation slightly.

Reset it: Safari → Settings → Privacy → Manage Website Data → Remove All. You’ll be signed out of sites (cookies go) but the DB is rebuilt fresh.

Less common: corrupted Safari preferences

If Safari is glitchy in addition to slow — windows opening in weird sizes, settings not saving, weird startup behaviour — its preferences might be corrupt. Try:

1. Quit Safari
2. cmd-shift-G in Finder, paste: ~/Library/Preferences/com.apple.Safari.plist
3. Move that file to your Desktop
4. Reopen Safari

It’ll start with default preferences. If that fixes the slowness, you can trash the old plist. If not, drag it back.

Also less common: a hung Safari Networking process

Sometimes the Safari “Networking” process gets stuck. In Activity Monitor, look for “com.apple.WebKit.Networking” — if it’s at 100% CPU constantly, Safari can’t load anything cleanly.

Quit Safari completely (cmd-Q, not just close window). Wait 5 seconds. Reopen. The Networking process restarts fresh.

Hardware: an overheated Mac throttles

If your Mac is hot — fans loud, vents warm — the CPU and GPU are throttling. Safari rendering is GPU-heavy in places, so a throttled Mac means a slow Safari.

Causes:

• Direct sunlight on the laptop
• Soft surface (bed, couch) blocking vents
• Dust clogged in fans (older Macs)
• A runaway process pegging CPU somewhere else

Check the CPU tab in Activity Monitor. If something unrelated is using 200% CPU, fix that first and Safari recovers.

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A practical fix order

When Safari is slow, work through these in this order:

1. Close tabs you don’t need (or save as Tab Group and close)
2. Disable extensions, re-enable one at a time
3. Use Window → Activity to find heavy pages, close them
4. Develop → Empty Caches
5. Update macOS
6. Restart Safari (cmd-Q, reopen)
7. Restart the Mac
8. As a last resort, move ~/Library/Preferences/com.apple.Safari.plist to Desktop and reopen

Most of these take seconds. The whole list is maybe 10 minutes if you go through everything.

What about resetting Safari?

Older versions of Safari had a “Reset Safari” menu option. It’s gone in modern macOS. The equivalent is:

1. Quit Safari
2. Move ~/Library/Containers/com.apple.Safari to your Desktop
3. Reopen Safari

That gives you a fresh Safari (no history, tabs, extensions). If problems are gone, trash the old folder. If not, restore it.

This is the nuclear option. Try everything else first.

Caches across the system

Safari’s not the only thing accumulating cache. macOS itself, every app you’ve ever run, and other browsers all leave caches in ~/Library/Caches/. On a Mac running for over a year, this can be 5-15 GB. Clearing this doesn’t directly speed Safari up, but it does free disk space, reduce indexing pressure, and make the whole system feel faster — which Safari benefits from.

The honest summary

Safari’s almost always fast on a current Mac with a current macOS, until you’ve accumulated tabs, extensions, and a year of cruft. The fix is:

• Tab discipline
• Extension audit
• Cache clear
• Keep the system current

Sweep handles the cache and cruft side automatically: caches across all browsers, log files, and forgotten files in a single scan, with a preview before anything goes. The tab discipline part is on you, but the rest can be a quick recurring cleanup.