macOS 10.13
Editing overview
Web Inspector allows you not only to filter resources but also to edit and save changes to resource files. Editing allows you to preview web content output with adjustments to HTML, CSS, and JavaScript code.
Elements tab: You can edit an HTML element and edit CSS rules, both with CSS blocks and visually.
Resources tab: You can edit CSS rules in stylesheet files and edit JavaScript in script files.
Note: To save any CSS or JavaScript changes made in Web Inspector to file, press Command-S.
See alsoEdit an HTML element