Types of links in SEO: dofollow, nofollow, sponsored, and UGC

When a website links to another, the browser renders the hyperlink the same way regardless of which attribute it carries. For Google's crawlers, however, the rel attribute on that link completely changes how the signal is interpreted. Understanding this distinction is a basic requirement for building a linkbuilding strategy that operates within Google's guidelines and correctly assigns value to each link.

What link attributes are and why Google introduced them

Link attributes are values added to the rel attribute of an <a> tag in HTML. Their purpose is to communicate information to search engines about the nature of a link: whether it was editorially placed, whether it is advertising, whether it comes from user-generated content, and so on.

Google introduced the nofollow attribute in 2005 to combat spam in blog comments. In September 2019, it expanded the system with two new attributes — sponsored and ugc — and simultaneously changed how it treats nofollow: it went from being a strict directive (ignore the link entirely) to being a hint that Google may or may not take into account at its own discretion. This change has practical consequences that many sites have yet to incorporate into their workflows.

"Link attributes are now treated as hints that we use to better understand how to handle links within Search." — Google Search Central, September 2019 update.

To understand the real weight of these attributes, it helps to have a clear picture of how authority propagates between pages. The article How PageRank works and its relationship with backlinks provides a technical framework for that mechanism.

The four types of link attributes

Dofollow (link without a restrictive attribute)

The term "dofollow" is technically incorrect: there is no rel="dofollow" attribute in the HTML specification. What the term refers to is simply a link that has not been assigned any restrictive attribute. Its code form is the most basic possible:

<a href="https://ejemplo.com">anchor text</a>

This type of link tells Google that it can crawl the destination and that the linking site editorially endorses that resource. These are the only links that, under normal conditions, transfer PageRank directly. That is why they are the focus of linkbuilding efforts: obtaining a dofollow link from a site with relevant authority remains a significant ranking signal.

However, the absence of an attribute does not guarantee that Google will process the link as a genuine endorsement. If the backlink profile pattern is artificial — for example, hundreds of identical links from sites with no real traffic — Google may choose not to process them regardless of the attribute.

Nofollow

Declared with rel="nofollow". Originally it functioned as a directive: the crawler was not supposed to follow that link or pass PageRank through it. Since the 2019 update, Google treats it as a hint. This means that in certain contexts it may still crawl and even factor in the link, though it is not required to do so.

<a href="https://ejemplo.com" rel="nofollow">anchor text</a>

nofollow remains the most widely used attribute in practice. It is recommended in the following scenarios:

• User comments where the quality of linked destinations cannot be audited.
• Social media profiles and forums where content is generated by third parties.
• Third-party widgets and plugins whose destination cannot be controlled.
• Linking to sites where there are quality or relevance concerns.
• Any situation where the site does not want to editorially endorse the destination.

One aspect that is often overlooked: many high-authority sites apply nofollow by default to all outbound links (Wikipedia being the most well-known example). This does not make a link from Wikipedia worthless; referral traffic and visibility still carry value even if PageRank does not flow directly.

Sponsored

Introduced in 2019, rel="sponsored" explicitly identifies that a link exists as part of a commercial relationship: advertising, sponsored content, paid articles, compensated collaborations, or any exchange of value for a link.

<a href="https://ejemplo.com" rel="sponsored">anchor text</a>

Google applies the same treatment as it does to nofollow — a hint not to pass PageRank — but with greater semantic specificity. The stated purpose is to allow the search engine to better distinguish between genuine editorial endorsement and promoted content, which theoretically enables it to calibrate the trustworthiness of a link more precisely.

Google's webmaster guidelines are explicit: links within paid content must carry rel="sponsored" or rel="nofollow". Publishing a dofollow link in exchange for money or any other consideration (free products, discounts, collaborations) violates Google's quality guidelines and can result in a manual penalty. This rule applies to both the site selling the placement and the site purchasing the link.

In the practice of editorial linkbuilding in LATAM, many news sites and digital media outlets apply nofollow or sponsored to sponsored posts. For a more detailed look at how these arrangements work in the regional market, the article What is linkbuilding and why it matters in SEO covers the full context.

UGC (User Generated Content)

rel="ugc" identifies links coming from user-created content: comments, reviews, forum threads, community replies, posts on open wikis. It was also introduced in 2019.

<a href="https://ejemplo.com" rel="ugc">anchor text</a>

Its primary use is technical and related to link profile hygiene. It allows platforms with user-generated content (Reddit-style forums, comment systems, marketplaces with reviews) to signal to Google that those links do not represent the platform's editorial judgment. Google treats these links similarly to nofollow.

From the perspective of someone building a site's backlink profile, ugc links offer diversification and naturalness value, but they should not be the primary component of a strategy. A profile composed mostly of ugc and nofollow links without editorial dofollow backlinks is a weak profile for competitive ranking purposes.

Combining attributes

Attributes are not mutually exclusive. It is possible — and in some cases recommended — to combine them. Google accepts the following combinations:

• rel="nofollow ugc" — for user-generated content where the classic nofollow is also applied for compatibility with other crawlers.
• rel="nofollow sponsored" — in contexts where the nofollow signal should be maintained while also indicating commercial nature.
• rel="ugc sponsored" — theoretically valid, though uncommon in practice.

For long-term implementations and sites operating across multiple regions in LATAM, it is advisable to document an internal link attribute policy that standardizes when each one applies. This reduces the risk of inconsistencies that could generate contradictory signals for the crawler.

Real impact on rankings: what the available evidence says

The practical question is not which attributes exist, but how much each one matters for rankings. The honest answer is that the impact is not precisely or publicly documented, because Google does not publish granular data on how it processes each link type. What can be stated based on available evidence:

• Dofollow links remain the most valued in linkbuilding strategies because they are the only ones that directly transfer PageRank under the crawler's standard behavior.
• Google has confirmed on multiple occasions — including public Search Central documentation — that nofollow has functioned as a hint since 2019, leaving open the possibility that some nofollow links from relevant sites are processed in some way.
• A natural backlink profile includes a mix of all attribute types. A profile composed exclusively of dofollow links can be a signal of artificiality to Google's systems.
• The sponsored attribute is not a penalty: it is simply contextual information. Properly declaring paid links protects the site from manual actions.

Ahrefs studies on backlink profiles of high-ranking sites consistently show that these sites have mixed attribute distributions, not 100% dofollow portfolios. This is consistent with the idea that profile naturalness matters as much as link volume.

Anchor text management is another factor that interacts directly with link type. A dofollow link with an over-optimized anchor can be more problematic than a well-contextualized nofollow. To see how to calibrate this variable, the article Anchor text: distribution, proportions, and how to avoid over-optimization covers the topic in depth.

Common mistakes in applying link attributes

Not declaring paid links with the correct attribute

The most common — and highest-risk — mistake is publishing sponsored content with dofollow links without disclosing the commercial nature of the relationship. Google is explicit on this point in its quality guidelines for webmasters. Manual penalties for link schemes can affect both the selling site and the buying site.

Treating nofollow as if it had no value whatsoever

Since 2019, assuming that a nofollow link is completely useless for SEO is an oversimplification. Google may process them as hints, and the referral traffic they generate has value independent of the attribute.

Ignoring attribution in user-generated content

Platforms that allow users to publish links without applying ugc or nofollow are sending confusing signals to crawlers and are vulnerable to having their outbound link profile exploited by spammers. Implementing the correct attribute in comment forms, reviews, and forums is a basic technical hygiene task.

Assuming that changing a link attribute takes immediate effect

Changes to link attributes require Google to re-crawl and re-index the page. On sites with a low crawl budget or high content volume, this can take weeks. Planning attribute changes with adequate lead time is part of proper execution.