Should you really mark all comment links with rel=UGC?

Why does Google emphasize rel=UGC for comments?

Google wants to distinguish editorialized links (those you choose and approve) from links that anyone can post on your site. Comments, forums, and user profiles are areas where link spam can proliferate without you having consistent manual control.

The rel=UGC (User Generated Content) attribute signals to the engine that these links come from a third party and should not be interpreted as a recommendation from you. Historically, rel=nofollow served this purpose — but since September 2019, Google introduced rel=ugc and rel=sponsored to refine link semantics. The nofollow attribute remains functional, but UGC is now the official tag for user content.

What are the risks if we don't mark these links?

If you allow dofollow links in comments, Google may consider that you are participating in an artificial linking scheme, especially if these links point to dubious sites or if the volume is significant. The consequences? A manual action for outgoing link spam, or even a general loss of trust in the site.

Even if you moderate comments, the volume might make manual verification unrealistic. Hence Google's recommendation: automate the addition of rel=UGC by default on all links posted by users. No manual moderation needed, no risk of oversight.

Does this guideline apply only to blog comments?

No. Google refers to user-generated content in a broad sense. This includes forums, Q&A sections, customer reviews, user profiles, collaborative directories, community wikis — in short, any area where a third party can insert a link.

The logic remains the same: if you don't control each link editorially, mark it with rel=UGC. It doesn't matter the CMS or platform: WordPress, Drupal, phpBB forums, custom sites — the rule applies everywhere. If your platform does not automatically handle this attribute, you will need to modify the code or install a plugin that does.

• rel=UGC is the official tag for any user-posted content (comments, forums, reviews)
• rel=nofollow remains functional if your CMS does not yet support UGC, but UGC is preferred for semantic clarity
• No risk of penalty if you follow this guideline — it's a protection, not a restriction
• Automate the addition of the attribute to avoid any forgetfulness or manual errors
• Check your existing UGC areas: comments, forums, profiles, reviews — and add rel=UGC wherever it's relevant

Is this guideline consistent with observed practices in the field?

Yes, and it aligns with a best SEO practice established for over 10 years. Even before the introduction of rel=UGC, serious sites were already using rel=nofollow on comments to avoid spam. The novelty here is that Google is formalizing a dedicated tag and insisting on its use.

In practice, sites that do not mark their UGC links do indeed receive manual actions if they accumulate outgoing link spam. Google Search Console regularly flags this type of alert. Conversely, there is no documented case of penalty for overusing rel=UGC — it's a defensive measure, not a restriction.

What nuances should be applied to this recommendation?

First point: rel=UGC does not mean the link is ignored. Contrary to what many still believe, Google has confirmed that nofollow, UGC, and sponsored are now treated as hints, not absolute directives. In other words, Google may choose to follow or not follow the link, to count it or not in PageRank — but it is no longer a strict block as it was before September 2019.

Second nuance: if you manually moderate each comment and validate links one by one, you might technically decide not to mark some links with UGC. But in practice, this is rarely realistic — and the risk of oversight is too high. Even with manual moderation, the safest approach remains to automate rel=UGC by default.

In what cases does this rule not apply?

If you have a closed system where only validated authors can post (for example, a multi-author blog with restricted access), then these links are not considered user-generated content — they are editorialized. No need for rel=UGC in this case.

Similarly, if you manage a highly-moderated forum where each link is manually checked before publication and you take ownership of the recommendation, you may choose not to mark these links. But let's be honest: that's rare and time-consuming. In 99% of cases, automating rel=UGC is the right approach to avoid any risk and any debate with Google.

What should you concretely do on your site?

First step: check if your CMS already automatically manages rel=UGC. WordPress, for instance, has been adding rel=nofollow by default to comments for years but does not automatically switch to UGC. Drupal, Joomla, and most modern forums (Discourse, recent phpBB) offer options to enable UGC.

If your platform doesn’t natively support rel=UGC, two solutions: install a plugin or modify the code. For WordPress, plugins like "Comment Link Attributes" or "UGC Link Attribute" allow you to force the addition of rel=UGC on all comment links. For a custom site, simply modify the function that displays comments to add the attribute via str_replace or directly in the HTML rendering.

What errors should be avoided during implementation?

A classic mistake: forgetting old UGC areas. If you've launched a forum five years ago, user profiles with biographies, or a Q&A section, check that all this content is well marked. A quick audit with Screaming Frog or a regex search in the database allows you to spot unmarked dofollow links.

Another error: combining rel=nofollow and rel=UGC on the same link. This is not catastrophic but unnecessary — UGC suffices. If your CMS adds both by default, don't panic: Google understands and takes into account the most specific attribute. But ideally, clean it up to keep clean code.

How to check that your site complies?

Inspect a few recent comments on your site, view the source code (right click > Inspect), and look for <a> tags. You should see rel="ugc" or at minimum rel="nofollow" on all links posted by users.

If you have a significant volume of comments, a filtered Screaming Frog crawl on the comment URLs allows you to quickly detect any suspicious dofollow links. You can also use Google Search Console: if you receive an alert for outgoing link spam, it is often linked to unmarked comments.

• Check that your CMS automatically adds rel=UGC (or nofollow) to comments
• Install a plugin or modify the code if necessary to enforce the attribute
• Audit old UGC areas (forums, profiles, reviews) and retroactively add rel=UGC if needed
• Test with a test comment: post a link, check the source code, verify the presence of the attribute
• Avoid combining rel=nofollow and rel=UGC — choose UGC preferably
• Monitor Google Search Console for any alerts of outgoing link spam