Search for a text string within files

At times you see that a particular image or so is not found when loading a web page and you are at a loss where the call came from. At least I had that today when I noticed that a menu image was called. The command to search for that is actually really straight forward:

grep -rnw 'directory' -e "string pattern"
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e.g. grep -rnw ‘public/’ -e mobile-menu.png