high safari cpu usage on macOS Sequoia 15.2

masen, 06 January 2025

After upgrading to macOS 15.2, I noticed that Safari CPU usage was consistently around 100% despite the not having any tabs open or extensions enabled.

To resolve the issue, I removed Favicon Cache directory from ~/Library/Safari.

  1. Make sure Safari is closed
  2. Open ~/Library/Safari
    1. From Terminal, open ~/Library/Safari
    2. From Finder, ⇧⌘G, ~/Library/Safari
  3. Move Favicon Cache to the trash

Investigation

I tried the usual clear browsing data trick and that didn’t seem to have any effect.

Checking the output of fs_usage -w Safari shows a lot of read traffic on a particular F=73 that unfortunately I didn’t catch the open of in all of my samples.

11:29:17.236585  read              F=73   B=0xa8      0.000002   Safari.40840
11:29:17.236587  read              F=73   B=0x8       0.000001   Safari.40840
11:29:17.236589  read              F=73   B=0x78      0.000001   Safari.40840
11:29:17.236594  read              F=73   B=0x8       0.000001   Safari.40840
11:29:17.236596  read              F=73   B=0x78      0.000001   Safari.40840
11:29:17.236599  read              F=73   B=0x8       0.000001   Safari.40840
11:29:17.236601  read              F=73   B=0x88      0.000001   Safari.40840
11:29:17.236606  read              F=73   B=0x8       0.000001   Safari.40840
11:29:17.236608  read              F=73   B=0x88      0.000001   Safari.40840

Eventually found the Stack Overflow Question Safari causes high CPU load for no reason, launchservicesd active and noticed a lot more open calls to the favicon cache database when Safari should have been essentially idle.

Thankfully this is a cache, not a data directory. So removing it as a test was enough to drop Safari back into idle usage with no otherwise ill effect.