Is it good practice to add rel="nofollow" to user supplied links such as in a question and answer site even if the link in question is relevant and of a high quality.

I will use Stack Exchange as an example here. Spammy links being added are generally caught and removed in short order by the extensive community moderation of all SE sites but links provided by users are still tagged for nofollow. Now the point of nofollow is to prevent pagerank from passing from the linking site to the linked to site, but if the linked to page is context appropriate and of a high value wouldn't it be better to allow the passing of pagerank?

Basically I am trying to work out here if a site should nofollow all user supplied links regardless of the quality and if so why?

  • How much time it will take to become a quality user? How much spammer will attract to site, if they know after XXXX points, our links will be dofollow. I can still see blackhat markets for reditt and quora. Here the links are turn into dofollow automatically, if the answer is high quality and have X number of upvotes. I am here just because the site have really super value. If SE do something about dofollow links, then I will say more n more marketing guys will use this site for promotion. And it's very hard to do moderation when answer is written in professional ways.
    – Goyllo
    Apr 25, 2017 at 5:34
  • Okay so the SE approach is to treat all links as nofollow to begin with but upgrade them to dofollow based on quality and the number of votes, didn't realise that. So if a site where to use a voting mechanism similar to SE to evaluate the quality of comments and answers it could be safe in that regard to remove the nofollow attribute from links in high voted posting. Apr 25, 2017 at 6:17
  • 1
    Yes, then it is safe. But SE consider up-votes only if it given by reputed member. Otherwise new member will create fake profile and up-votes their own answer to turn link into dofollow. You need to do some analysis to know how SE/SO handle links. It's really impressive.
    – Goyllo
    Apr 25, 2017 at 8:17
  • Might have to meta it and ask for the broad strokes Apr 25, 2017 at 10:35

2 Answers 2


if the linked to page is context appropriate and of a high value wouldn't it be better to allow the passing of pagerank?

Quite probably yes. But unfortunately, in the real world, for arbitrary user submitted content on a high traffic website, this is near impossible to guarantee. Trying to manually moderate the outbound links in such fine detail would be too time-consuming with little gain IMO.

Even if the linked content is "high value", it could be self-promoting or have some affiliation (which might even be disclosed in the post itself). All of which is near impossible to moderate with any degree of automation.

If it is known that "some" links are do-follow then it will increase the incentive to try to game the system and make it even harder to moderate.


Here are some options that make you situation safe with google and other search engines:

  1. If you have no script programming experience (For example, if you build websites using point-and-click operations in the wordpress interface instead of writing code in PHP to produce webpages), then your best bet is to make every user-submitted link have the no-follow attribute, and then manually have your moderators change the quality links so they no longer have the no-follow attribute.


  1. Create server code that scans the text contents of the webpages the submitted URL's point to and then have it check the retrieved text against your regulations and search engines regulations to determine if it is acceptable. If it is not, then either add the no-follow attribute to the link, or if the link is terrible, you could reject the link (have it not displayed).

For example, if your site is about fruits and a user submits a URL to a bicycle shop, then your script would add a no-follow attribute to the URL because the text in the URL never mentions fruits. just bikes. You can also setup your script to include filters so that if a user submits a URL about adult material, you can easily reject it, just because a word found in the webpage of the submitted URL matches a forbidden word (example: sex).

Do understand that if you don't use the no-follow attribute, then the links are assumed to be "follow"-able. This means google and other search engines assume they have permission to access the links that aren't marked "no-follow". For this reason, I'd recommend one of my two approaches, because if you allow link-following by default and you have no programming experience, but instead moderators, then guests could submit unacceptable material (for example, a link to sex material), and next thing you know, search engines could crawl that and possibly lower your ranking in search engines, just because your moderators won't have a chance to remove the bad link in time.

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