I found the /_locales/ directory in the following location: ~/Library/Caches/com.apple.Safari/Extensions/Evernote Web Clipper.safariextension/_locales -- Seems we're discussing two separate error messages in this thread... I'm not a programmer, so I've not a solid understanding of how they are connected: #1: the error related to the language localization (original post by joeworkman) #2: the error related to cross origin requests (added by Tschügge) For me, duplicating the /en/ directory and renaming /en_US/ seems to work as a hack for removing the console log Errors in #1 (thanks Rodrigo Passos!). After creating the /en_US/ directory, I then began receiving console log Warnings from BOTH /en/messages.json and /en_US/messages.json regarding insecure content. These insecure content errors seem to trace back to a file named "port.js" and specifically to Line 152, which seems to be involved in a variable named "c" as defined: var c = new XMLHttpRequest; As jbignert noted, the port.js file is indeed located in the /third_party/ directory... however, the first line of port.js reads: /*! Copyright 2009-2017 Evernote Corporation. All rights reserved. */ FWIW, a second file named jsonrpc.js located in /third_party/ also includes the above copyright notice.