It was deployed alongside the rel="sponsored" attribute as an evolution of the traditional, monolithic nofollow tag.
Why Google Created the UGC Tag
For nearly 15 years, the rel="nofollow" tag was the absolute gold standard for dealing with untrusted links. If a user dropped a spammy link to an unregulated pharmacy in your blog's comment section, your CMS automatically appended nofollow to it. This explicitly commanded Google: "Do not crawl this, do not trust this, and do not pass any PageRank equity to this destination."
However, this created a massive blind spot for Google's algorithm. By entirely blocking equity flow through comment sections, forums, and Q&A sites (like Wikipedia, Reddit, and Quora), Google lost access to a massive trove of link telemetry.
In 2019, Google transitioned nofollow from an "absolute directive" to a "hint." Simultaneously, they introduced rel="ugc" to provide themselves with better systemic context.
If a link is tagged with ugc, Google knows the site owner isn't directly vouching for the link, but Googlebot may still choose to crawl it or pass slight equity if the destination is verified as highly authoritative.
Where You Should Use rel="ugc"
As a webmaster, you should deploy the UGC attribute programmatically on any platform where unvetted users can alter the HTML payload of your domain.
- Blog Comments: Any URL submitted by a reader in a comment form should automatically output
<a href="https://example.com" rel="ugc">. - Forum Posts: Message boards (like phpBB or Discourse) should append this to all user-submitted hyperlinks.
- User Profiles: If you allow users to create an account and link back to their "personal website" in their bio, that link must be heavily restricted to prevent automated spam bot registrations.
Pro-Tip: You Don't Have to Rewrite History When Google introduced the UGC and Sponsored tags, panic erupted in the SEO industry. Site owners thought they had to retroactively scour millions of old forum posts and change
nofollowtougc. You absolutely do not need to do this. Google has explicitly stated that fallbacknofollowtags are perfectly fine. You only need to consider implementingugcfor new code deployments or native CMS updates.
Combining Link Attributes
It is totally acceptable, and often recommended for backwards compatibility with minor search engines (like Bing or Yandex) that might not process the newer tags effectively, to stack relational link attributes.
If a user posts a comment linking to a highly suspicious casino website, your system can safely append both tags:
<a href="http://spam-casino.com" rel="nofollow ugc">
This ensures that the link is classified specifically as user-generated content for Google, while providing an absolute block for legacy crawlers that only understand the historic nofollow directive.