I use MacOS Safari's Responsive Design Mode for web development (Command-Option-R or 'Develop' > 'Enter Responsive Design Mode' in the menu.

I have "accidentally" changed the largest window size to a random size (should be 1920 x 1080) by adjusting the horizontal and vertical handles. I would like to reset to 1920 x 1080, but it is very difficult to do by adjusting the handles because of the responsiveness of the controls; it's hard to stop on a specific dimension. Unfortunately, that is the only way I can see to do it, as I can't find a reset control or option anywhere?

I have searched the menu options and the almighty Google and can't seem to find an answer? I suspect there is .plist I can remove? Could someone point me in the right direction?

2 Answers 2


.This setting is written to Safari's preferences, that are located in ~/Library/Preferences/com.apple.Safari.plist in dictionary by ResponsiveDesignCustomPresetConfigurations key. So if you need to reset all responsive mode settings - just close Safari and delete that dictionary from prefs .plist file with following terminal command:

defaults delete ~/Library/Preferences/com.apple.Safari.plist ResponsiveDesignCustomPresetConfigurations
  • 1
    My-MBP:proj michael$ defaults delete ~/Library/Preferences/com.apple.Safari.plist ResponsiveDesignCustomPresetConfigurations 2018-09-22 16:17:20.229 defaults[9413:941183] Domain (/Users/michael/Library/Preferences/com.apple.Safari.plist) not found. Defaults have not been changed. Commented Sep 22, 2018 at 23:19

The responsive design mode can be reset by removing the ResponsiveDesignCustomPresetConfigurations in com.apple.Safari.plist. The plist file location depends on the versio OS.

macOS 10.15 Catalina (and 10.14)

  • Go to System Preferences → Security and Privacy
  • Enable Full Disk Access for Terminal
  • Run the following command
    defaults delete ~/Library/Containers/com.apple.Safari/Data/Library/Preferences/com.apple.Safari.plist ResponsiveDesignCustomPresetConfigurations

If full disk access is not enabled, the plist file cannot be found, read or written to.

macOS 10.13 and earlier

Editing the file can be done using the plist file in: ~/Library/Preferences/com.apple.Safari.plist

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