Here’s how:

kick off the iPhoneSettingsmenu.

Scroll to the bottom of the page and selectAdvanced.

Move theWeb Inspectortoggle switch to theOnposition.

An iPhone showing how to turn on the Safari Web Inspector

With Safari open, selectSafarifrom the menu bar and choosePreferences.

Select theShow Develop menu in menu barcheck box and end the configs window.

What Is Web Inspector?

Safari with the Preferences menu item highlighted

Web developers use Web Inspector to modify, debug, and optimize websites on Macs and iOS devices.

With Web Inspector open, developers can inspect the resources on a web page.

Recent versions of iOS use Web Inspector instead.

Safari preferences with the Advanced tab highlighted

With Safari 9 and OS X Mavericks (10.9), Apple introducedResponsive Design Modein Web Inspector.

Safari advanced settings with the “Show Develop Menu” option highlighted

Safari mobile Web Inspector activated from the Develop menu on macOS