Google Chrome currently requires several tags to make an (HTML5) document opt out of translation. Before doing this, you should be sure that you know your audience's language, as otherwise it will prevent foreign sites from properly translating your site.
The relevant tags are:
<meta charset="UTF-8" />
<meta name="google" content="notranslate" />
<meta http-equiv="Content-Language" content="en_US" />
And here is a full example:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="google" content="notranslate" />
<meta http-equiv="Content-Language" content="en_US" />
</head>
<body>
Dies ist ein Test Deutsch
</body>
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