The rel attribute specifies the relationship between the current document and the linked document. Search engines can use this attribute to get more information about a link.
rel Attribute Values
nofollow | Links to an unendorsed document, like a paid link. (“nofollow” is used by Google, to specify that the Google search spider should not follow that link) |
noreferrer | Requires that the browser should not send an HTTP referer header if the user follows the hyperlink |
noopener | Requires that any browsing context created by following the hyperlink must not have an opener browsing context |
Add the following code into your HTML page between the <head> and </head> tags or before the closing </body> tag
<script>
document.addEventListener('DOMContentLoaded', function () {
var links = document.getElementsByTagName("a");
var i;
for (i = 0; i < links.length; i++) {
if (location.hostname !== links[i].hostname) {
links[i].rel = "nofollow noopener noreferrer";
links[i].target = "_blank";
}
}
});
</script>