# Nofollow vs dofollow links: every type of link, explained

> Nofollow, dofollow, sponsored, UGC: what each link type and rel attribute really does in 2026, what Google says, what experiments show, the penalties, and how one site applies it.

Source: https://contenttosocial.com/guides/nofollow-links  
Updated 2026-10-01 · 22 min read

A link is a path, a vote and a label at once. **Internal links** join your own pages, **outbound links** point to other sites, and **backlinks** are other sites pointing to yours. The `rel` attribute qualifies a link: without it, you vouch for the destination; `nofollow`, `sponsored` and `ugc` tell Google you don’t. “Dofollow” is not an attribute: it is just a normal link.

Here is what each kind and each attribute really does in 2026, from Google’s own documents and engineers, from controlled experiments and from a court record, with the penalties, the law on paid links, and how this site makes those choices in its code.

### A link, taken apart

```html
<a href="https://example.com" rel="sponsored" target="_blank">the anchor text</a>
```

1. **The destination**: The address Google can crawl. Without a real `href`, there is no link for it.
2. **The relation**: What you vouch for. Nothing means yes; `nofollow`, `sponsored` or `ugc` mean no.
3. **The new tab**: A comfort for readers. Browsers now add `noopener` on their own.
4. **The anchor text**: The words Google reads as the destination’s label.

Only the relation changes how Google counts the link. The rest decides whether it can, and what it learns.

- **2005**: Year nofollow was born
- **32.3%**: Pages with a nofollow link
- **0.5%**: Pages using sponsored or ugc
- **43 · 6**: Median internal · external links per page
- **66.5%**: Links lost since 2013

## Three directions, four relations.

Every link has a direction, depending on where it starts and where it lands, and a relation, the `rel` attribute, which says whether its author vouches for it. Most confusion comes from mixing the two: “backlink” is a direction, “nofollow” a relation. A backlink can be nofollow; an internal link should almost never be.

- **Internal links** (Your page → your page): They build the paths through your site: menus, breadcrumbs, links in the text. They decide which pages Google finds, how often it comes back, and how importance spreads. You control all of them.
- **Outbound links** (Your page → another site): Also called external links. They cite, credit or sell. Each one says, through its `rel`, whether you vouch for the destination. They don’t cost you rankings.
- **Backlinks** (Another site → your page): Also called inbound links. The ones search engines learned to count first, and the ones people try to buy. You control none of them, which is exactly why they are worth something.

## Less than in 2005, more than Google likes to say.

Google was built on links. The PageRank patent, filed in January 1998, treated each link as a vote, weighted by the importance of the page casting it; the paper that presented Google the same year also credited a link’s anchor text to the page it points to. Twenty-eight years later, both ideas still run.

Google’s engineers have spent years lowering expectations. Gary Illyes said in 2023 that links were no longer a top-three ranking factor, and in 2024 that Google needs “very few links to rank pages”. Its spam policy page once called links “an important factor”, then “a factor”, then dropped the sentence in September 2024.

Then came a court record. In the 2025 remedies phase of the US antitrust case against Google, notes from a call with a Google engineer described anchors (“a source page pointing to a target page”) as one of three core signals of topicality, and PageRank as a signal of distance from known good sources that feeds a quality score. Links still matter; each one simply matters less, and what counts is where it comes from.

Two details from Google’s own podcast undo common beliefs. The PageRank Google computes is not the 0-to-10 score its old toolbar showed: Gary Illyes describes an integer from 0 to “65,000-something”, and says of the toolbar number: “That’s never what we’ve been using.” And Google has no domain score: Domain Rating and Domain Authority are tools’ estimates. “It’s not our domain score. We don’t have that,” Danny Sullivan says.

> “We need very few links to rank pages.”
>
> — Gary Illyes, Analyst, Google Search. [SERP Conf 2024](https://www.youtube.com/watch?v=DJVaGCZLmt8)

- **0.255**: Correlation between the number of referring domains and ranking, the strongest link measure in a study of 1 million keywords. Real, and modest. (Ahrefs, January 2025)
- **2,997**: Pages, out of about 20 million with no links from other sites, that get more than 1,000 search visits a month. Almost all sit on strong sites, on easy queries. (Ahrefs, December 2023)
- **94%**: Google AI Overviews that cite at least one page from the top 20 results. Ranking, which links help, still feeds the AI answers. (seoClarity, October 2025)

## What each rel value really says.

The `rel` attribute describes your relation to the page you link to. Google reads four answers. You can combine them with spaces (`rel="ugc nofollow"`), and since September 2019 Google treats all three qualifiers as hints rather than orders: it may still use such a link to discover a page. Its documentation today still says these links “will generally not be followed”: assume they pass nothing.

| rel |  | What it says | What Google does | When to use it |
| --- | --- | --- | --- | --- |
| `(none)` | A normal link | “I vouch for this page.” What people call a “dofollow” link: there is no such attribute. | Follows it, counts it toward PageRank and reads its anchor text as a label for the destination. | Your own pages, and every source you cite and stand by. |
| `nofollow` | No endorsement | “I don’t vouch for this page.” Born in January 2005, with Yahoo and MSN, against blog comment spam. | A hint since 2019 for ranking, since March 2020 for crawling. Generally not followed, not credited. | Links you can’t vouch for and that are neither paid nor user-posted. Never your own pages. |
| `sponsored` | Paid or gifted | “This link exists because of money, a gift or a deal.” Added in September 2019; `nofollow` remains acceptable. | The same treatment as nofollow. The only case where the wrong attribute is a problem: an unmarked paid link. | Ads, paid placements, affiliate links, links in exchange for a product or a discount. |
| `ugc` | Posted by users | “A visitor put this link here, not us.” Added in September 2019. | The same treatment as nofollow. Google suggests lifting it for members with a record of good contributions. | Comments, forum posts, reviews, profiles. |

### noopener and noreferrer are not SEO

`noopener` stops the page you open from controlling yours through `window.opener`. Since Safari 12.1 (2019), Firefox 79 (2020) and Chrome 88 (2021), browsers apply it by themselves to every `target="_blank"` link. `noreferrer` goes further: it also hides where the visitor came from, so the site you link to sees a “direct” visit.

Neither changes how Google counts a link. When Google made nofollow a hint, Gary Illyes said it was catching up: the other big search engines already treated it that way. Note too that `sponsored` and `ugc` aren’t in the HTML standard: they are search-engine conventions, and almost nobody uses them, with each on 0.5% of pages against 32.3% for `nofollow` (HTTP Archive, 2025).

> “I would be very surprised if there was any big social media site out there with dofollow links that we haven’t already marked as nofollow internally for ourselves.”
>
> — Gary Illyes, Google Search, on links from social platforms. [Search Off the Record, episode 23](https://search-off-the-record.libsyn.com/website/seo-starter-guide-whats-all-the-drama)

## Internal links: the paths you control.

Internal links are the one lever you fully control. They tell Google which pages exist (a page no other page links to, an orphan, may never be found), how important each is, and what it is about through the words of the anchor. Google’s own advice is short: every page you care about needs a link from at least one other page of your site, and there is “no magical ideal number of links”.

Two technical rules matter more than any strategy. Google only follows real `<a href>` elements: a `<span>` with a click handler, a `javascript:` address or a router call without `href` is invisible. And `nofollow` on your own pages saves nothing: since about 2008, the share of importance given to a nofollowed link simply disappears, which is why Matt Cutts told site owners in 2009 never to use it inside their site. In 2020, 35.3% of the top 110,000 sites still did.

When one page links twice to the same address, Google may keep only the first anchor (tests by Zyppy, 2023): a menu link earlier in the code can win over the descriptive one in your text.

> “In general, whenever you’re linking around within your site: don’t use nofollow.”
>
> — Matt Cutts, Then head of web spam, Google. [PageRank sculpting, June 2009](https://www.mattcutts.com/blog/pagerank-sculpting/)

- **+7%**: Organic traffic after adding links to nearby location pages, in a controlled split test on about 8,000 pages. (SearchPilot)
- **+11%**: From showing four related articles instead of two at the end of each page, at 90% confidence. (SearchPilot)
- **≈ 5×**: Traffic for pages with at least one exact-match internal anchor, over 23 million internal links on 1,800 sites (a correlation). (Zyppy, 2022)

## Outbound links: cite, and say what you vouch for.

Linking out doesn’t cost you rankings, and Google’s documentation says citing your sources can help establish trust. John Mueller has also said outbound links are not a ranking factor as such. The only experiment usually quoted for the opposite, Reboot Online’s, used ten new domains and invented keywords: suggestive, too small to settle anything.

The real decision is the `rel`. Google asks for `nofollow` only “when you don’t trust the source, and not for every external link”. Blanket nofollow, the policy many publishers adopted (Forbes and Inc. switched every external link in 2017), is what made Google turn nofollow into a hint: it was losing information. Nicholas Carr called Wikipedia’s 2007 switch a black hole that soaks up links and never gives any back.

### Leave the link normal

- A source you read and stand by.
- A tool, study or person you recommend.
- Your own other sites, if they are genuinely related.

### Qualify the link

- `sponsored`: anything paid, gifted, discounted or affiliate.
- `ugc`: anything a visitor posted.
- `nofollow`: anything you can’t vouch for.
- `noreferrer`: only if the destination mustn’t know you sent the visit.

### Paid links need two labels: one for Google, one for people

`rel="sponsored"` satisfies Google; it doesn’t satisfy the law. In the United States, the FTC’s Endorsement Guides ask for a disclosure that is hard to miss, next to the link: “paid link” works, a hyperlinked disclosure or a note on the home page doesn’t.

In France, the June 2023 law on influencers, amended in November 2024, requires a clear, legible mention of commercial intent, such as « Publicité » or « Collaboration commerciale », and the Consumer Code treats paid editorial content and paid rankings as misleading practices when undisclosed. Online, penalties reach five years and €750,000.

## Backlinks: earned, not bought.

A backlink is worth something because you didn’t place it. That is also why people try to manufacture them, and why Google’s spam policy defines link spam as links created “primarily for the purpose of manipulating search rankings”. Since Penguin 4.0 in 2016, Google mostly ignores such links instead of punishing the site; links bought from a network are nullified as soon as they are seen, without notice. The buyer can’t tell what they paid for.

What earns links is something worth citing. Studies by Moz and BuzzSumo found that original research and opinion earn the most, and that most published posts, around three quarters, earn none at all. A nofollowed mention on a big site can still bring followed links: when other journalists pick up the story, some link with no attribute.

### What Google lists as link spam

- Buying or selling links that pass ranking credit, including a free product in exchange for a link.
- Excessive link exchanges and partner pages.
- Optimised anchors in guest posts, articles and press releases.
- Keyword-rich, hidden or low-quality links in widgets spread across sites.
- Links required by terms of service, with no way to qualify them.
- Widely distributed links in the footers or templates of many sites.
- Low-quality directory, bookmark and forum signature links.

### The disavow tool is for emergencies

Google says most sites will never need it: it is for a considerable number of spammy links that caused, or will likely cause, a manual action. John Mueller called the idea of “toxic links” something made up by SEO tools. One practitioner disavowed his entire link profile twice: in 2013 the site sank; in 2024, nothing happened in seven weeks.

### And AI search?

AI answers run on search: they send “a whole bunch of searches for you”, in Danny Sullivan’s words, and cite pages from the results, so whatever helps a page rank helps it get cited. In Ahrefs’ study of 75,000 brands, mentions correlate most with visibility in AI Overviews (0.664), raw backlinks much less (0.218), but links that name the brand come second (0.527). Google warns that seeking inauthentic mentions isn’t as helpful as it seems, and since May 2026 its spam policies explicitly cover manipulating generative AI answers. Agents that act on a page rather than cite it are another story, told in our [WebMCP guide](https://contenttosocial.com/guides/webmcp).

### When it went wrong

- **2011, J.C. Penney.** The New York Times found 2,015 pages linking with “dresses” and similar anchors. Google acted by hand; Penney fired its SEO firm. Outsourcing the work doesn’t outsource the risk.
- **2011, Overstock.** Discounts for students and staff in exchange for links from university sites. About two months penalised. Discounts count as payment.
- **2012, Google Chrome.** An agency paid bloggers for posts with a followed link to Chrome’s download page. Google demoted its own page for 60 days.
- **2013, Interflora.** About 150 advertorials in UK regional newspapers. Interflora vanished from Google UK, and the newspapers lost PageRank too: selling gets punished as well.

> “Disavowing random links that look weird or that some tool has flagged, is not a good use of your time. It changes nothing.”
>
> — John Mueller, Search Advocate, Google. [SEO office hours, November 2022](https://www.youtube.com/watch?v=TepFVYrBVg0)

## From a vote to a hint.

Twenty-eight years of the same idea, and of people gaming it.

- **1998, PageRank.** Larry Page files the patent on January 9. The paper presenting Google, in April, counts each link as a vote and credits its anchor text to the target page.
- **Jan 18, 2005, nofollow is born.** Google, with Yahoo and MSN, introduces `rel="nofollow"` to take the reward out of blog comment spam.
- **Jan 2007, Wikipedia closes the tap.** English Wikipedia makes every external link in its articles nofollow.
- **Jun 2009, Sculpting ends.** Matt Cutts reveals that, since about a year earlier, nofollowed links no longer pass their share of PageRank to the others: nofollowing internal links no longer “sculpts” anything.
- **2011–2013, Public penalties.** J.C. Penney, Overstock, Interflora and Rap Genius lose their rankings over bought or traded links; Google demotes its own Chrome page in 2012.
- **2012, Penguin and disavow.** Penguin (April 24) targets link spam, affecting about 3.1% of English queries. The disavow tool follows on October 16.
- **2016, Devalue, don’t demote.** The public toolbar PageRank score is retired. Penguin 4.0 (September 23) runs in real time and discounts bad links rather than demoting whole sites.
- **Sep 10, 2019, sponsored, ugc, and hints.** Google adds `sponsored` and `ugc` and turns all three values into hints for ranking, then for crawling from March 1, 2020.
- **Dec 2022, SpamBrain.** The last update dedicated to links uses SpamBrain to spot both sites buying links and sites selling them.
- **2023–2024, Links matter less.** Gary Illyes: links aren’t top three (2023), Google needs very few (2024). The spam policy drops “an important factor”. Leaked documentation shows link fields such as `pagerankNs` and anchor spam scores, without their weights.
- **2025–2026, Confirmed, and extended to AI.** The US antitrust record confirms PageRank and anchors still feed ranking. In May 2026, spam policies cover generative AI answers; from August 30, site reputation abuse no longer brings manual actions inside the EEA.

## What most articles get wrong.

- ~~“Add rel="dofollow" to your links.”~~ The value doesn’t exist. A link without `rel` is followed.
- ~~“Nofollow keeps your PageRank at home.”~~ Since about 2008 the nofollowed share simply evaporates.
- ~~“Nofollow keeps a page out of Google.”~~ Only `noindex` does, on a page Google may crawl.
- ~~“Nofollow is wrong for paid links.”~~ Still acceptable; `sponsored` is only preferred.
- ~~“noopener and noreferrer help SEO.”~~ Security and privacy only; `noreferrer` hides you from the destination’s analytics.
- ~~“sponsored and ugc are HTML standards.”~~ They are search-engine conventions, on 0.5% of pages.
- ~~“Disavow toxic links every quarter.”~~ Only for a manual action, or a real risk of one.
- ~~“rel="sponsored" is my legal disclosure.”~~ People need a visible label next to the link.
- ~~“Domain Authority is Google’s score.”~~ It is a tool’s estimate. Google says it has no domain score.
- ~~“301 redirects lose PageRank.”~~ Google says no PageRank is lost, with a 301 or a 302.
- ~~“A sitemap replaces links.”~~ It only says a page exists; a link also says who vouches for it.
- ~~“Links are dead” or “links are top three”.~~ Both wrong: fewer links count, and they still do.

## How this site links.

Contenttosocial publishes three kinds of pages that link a lot: a ranking of SEO agencies, a catalogue of social post templates and these guides. Every link on them carries a decision. Here are ours, straight from the code.

### Seven links, seven decisions

- **Their Google reviews** (`nofollow noopener`): A convenience for the reader, not a recommendation.
- **“Ask ChatGPT, Claude, Perplexity, Gemini” buttons** (`nofollow noopener`): Each opens an agent with a prompt in its address: endless one-off URLs nobody should crawl or credit.
- **The sources of these guides** (`(none)`): Editorial citations we read and stand by: Google’s documentation, papers, talks. Exactly what a normal link is for.
- **Menus, footer, breadcrumbs** (`(none)`): The footer lists every templates page, the header leads to every guide, and every page carries a breadcrumb with its structured data. Nothing that matters sits more than three clicks from home.
- **Pages waiting for launch** (`noindex, follow`): Kept out of Google’s index with a robots tag, not with nofollow, while their links are still followed so no page becomes an orphan.
- **The badge agencies may add to their site** (`one visible link`): Optional and never a condition of being listed; one visible link back to the page the award refers to, nothing hidden.
- **Every navigation link** (`<a href>`): Next.js `<Link>` renders a real anchor with its address, so crawlers follow the same paths as people.

### What it taught us

1. **Decide per destination, not per site.** The same site can deserve a normal link on one page and a nofollow on another: the relation is about the link and its context, not the domain.
2. **Hide pages with robots, not with links.** `noindex, follow` keeps a page out of results without cutting the paths through it.
3. **Leave referrers alone.** Dropping `noreferrer` costs nothing and lets the sites you send visits to see them. They may link back.
4. **A link in an iframe isn’t a link on the host page.** Google credits it to the iframe’s own page. Anything you embed elsewhere needs its link in the host’s HTML.

### What we don’t know yet

How many backlinks the ranking will earn, and which ones Google will count. We will watch Search Console knowing its links report is a sample: tables stop at 1,000 rows, and it doesn’t say which links are nofollow.

See the choices live: [SEO agency ranking](https://contenttosocial.com/seo-agencies), [Free templates](https://contenttosocial.com/templates), [All guides](https://contenttosocial.com/guides).

## Twelve rules that hold up.

From Google’s documentation, the experiments and our own code.

1. **No orphans.** Link every page you care about from at least one other page of your site.
2. **Real links only.** `<a href>` with an address. No click handlers, `javascript:` or router calls without `href`.
3. **Say where it goes.** Descriptive, concise anchors. No “click here”, no stuffing, no chains of adjacent links.
4. **Never nofollow yourself.** To keep a page out of Google, use `noindex`; to keep crawlers away, robots.txt.
5. **Cite with normal links.** Nofollow only what you can’t vouch for, not every external link.
6. **Label every paid link twice.** `sponsored` (or `nofollow`) for Google, and a visible “paid link” or « Publicité » for people.
7. **Qualify user links.** `ugc` on comments and forums; consider lifting it for trusted contributors.
8. **Never buy, swap or require.** No paid followed links, no link exchanges at scale, no links demanded by terms or badges.
9. **Keep widget links honest.** One visible link, named after a brand or a page, never keyword-stuffed, never mandatory.
10. **Don’t hide your referrals.** `target="_blank"` already implies `noopener`; skip `noreferrer` unless you need it.
11. **Fix what rots.** Two links in three published since 2013 are gone. Check yours.
12. **Leave disavow alone.** Unless you have a manual action, or real reason to expect one.

## Frequently asked questions

### What does a nofollow link mean?

A link with `rel="nofollow"`: its author tells search engines they don’t vouch for the page it points to. Google treats it as a hint and generally doesn’t follow it or credit it toward ranking.

### What is a dofollow link?

A normal link, with no `rel` qualifier. “Dofollow” isn’t an attribute; `rel="dofollow"` does nothing. Search engines follow and credit links by default.

### Do nofollow links help SEO?

Not directly, by default: they generally pass no ranking credit. They can still bring visitors, get a page discovered, build a brand, and lead to followed links when others pick up the story.

### How can I tell if a link is follow or nofollow?

Look at the link’s HTML (right-click, Inspect): if its `rel` contains `nofollow`, `sponsored` or `ugc`, it is qualified; otherwise it is a normal, followed link. Search Console’s links report doesn’t tell you.

### What is the difference between nofollow, sponsored and ugc?

The reason. `sponsored` marks paid or gifted links, `ugc` links posted by users, `nofollow` anything else you don’t vouch for. Google treats the three the same way; only an unmarked paid link is a problem.

### Should internal links be nofollow?

No. It saves nothing, since the nofollowed share of importance just disappears, and it can hide pages from Google. Use `noindex` or robots.txt for pages you want out.

### Are backlinks good or bad?

Earned ones help, especially from relevant, trusted sites. Bought or manufactured ones are mostly ignored since 2016, and can bring a manual action. You don’t need many: Google says it needs very few links to rank a page.

### Is rel="sponsored" enough to disclose a paid link?

For Google, yes (or `nofollow`). For the law, no: the FTC in the US and French law require a visible mention for readers, such as “paid link” or « Publicité », next to the link.

### Do noopener and noreferrer affect SEO?

No. `noopener` is security, which browsers now apply to every `target="_blank"` link by themselves; `noreferrer` hides the origin of the visit from the destination’s analytics.

## Where this comes from

Quotes are verbatim from the documents and recordings below, trimmed for length; quotes from conference talks come from automatic captions. Figures name who measured them, and correlations are labelled as such.

- [Qualify your outbound links to Google](https://developers.google.com/search/docs/crawling-indexing/qualify-outbound-links) — Google Search Central, 2025-12-10
- [Link best practices for Google](https://developers.google.com/search/docs/crawling-indexing/links-crawlable) — Google Search Central, 2025-12-10
- [Spam policies: link spam](https://developers.google.com/search/docs/essentials/spam-policies#link-spam) — Google Search Central, 2026-08-28
- [Evolving nofollow: new ways to identify the nature of links](https://developers.google.com/search/blog/2019/09/evolving-nofollow-new-ways-to-identify) — Google Search Central blog, 2019-09-10
- [Preventing comment spam (the birth of nofollow)](https://googleblog.blogspot.com/2005/01/preventing-comment-spam.html) — Google blog, 2005-01-18
- [Penguin is now part of our core algorithm](https://developers.google.com/search/blog/2016/09/penguin-is-now-part-of-our-core) — Google Search Central blog, 2016-09-23
- [Disavow links to your site](https://support.google.com/webmasters/answer/2648487) — Google Search Console Help, 2026
- [Updating the site reputation policy in the EEA](https://developers.google.com/search/blog/2026/08/update-site-reputation-policy) — Google Search Central blog, 2026-08
- [Link types](https://html.spec.whatwg.org/multipage/links.html) — WHATWG HTML Standard, 2026
- [rel=noopener](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes/rel/noopener) — MDN Web Docs, 2026
- [Web Almanac 2025: SEO](https://almanac.httparchive.org/en/2025/seo) — HTTP Archive, 2025
- [US v. Google: remedies opinion](https://storage.courtlistener.com/recap/gov.uscourts.dcd.223205/gov.uscourts.dcd.223205.1436.0.pdf) — US District Court for D.C., 2025
- [PageRank sculpting](https://www.mattcutts.com/blog/pagerank-sculpting/) — Matt Cutts, 2009-06-15
- [The decay and fall of guest blogging](https://www.mattcutts.com/blog/guest-blogging/) — Matt Cutts, 2014-01-20
- [Nofollow as a hint, sponsored and ugc](https://www.youtube.com/watch?v=78GFh553Vbc) — Google Search News, John Mueller, 2019-09
- [Search Off the Record, episode 1: nofollow](https://www.youtube.com/watch?v=3Ofp48EJxrU) — Google, with Gary Illyes, John Mueller, Martin Splitt, 2020
- [Search Off the Record, episode 8: rendering, signals and PageRank](https://search-off-the-record.libsyn.com/website/what-do-rendering-signal-collection-and-seos-devs-have-to-do-with-each-other) — Google, with Gary Illyes and Martin Splitt, 2020-10-22
- [Search Off the Record, episode 20: tackling web spam](https://search-off-the-record.libsyn.com/website/tackling-web-spam-search-quality-and-more) — Google, with Duy Nguyen, 2021-07-06
- [Search Off the Record, episode 23: the SEO Starter Guide](https://search-off-the-record.libsyn.com/website/seo-starter-guide-whats-all-the-drama) — Google, with Gary Illyes and John Mueller, 2021-09-09
- [Search Off the Record, episode 51: redirects](https://search-off-the-record.libsyn.com/website/lets-talk-redirects) — Google, with Martin Splitt and John Mueller, 2022-11-17
- [Search Off the Record, episode 102: SEO, AIO and GEO](https://search-off-the-record.libsyn.com/website/seo-aio-geo-your-site-third-party-support-to-optimize-for-llms) — Google, with John Mueller and Danny Sullivan, 2026-01-08
- [Gary Illyes Q&A](https://www.youtube.com/watch?v=DJVaGCZLmt8) — SERP Conf 2024, 2024
- [SEO office hours (disavow)](https://www.youtube.com/watch?v=TepFVYrBVg0) — Google Search Central, 2022-11
- [PageRank sculpting at SMX Advanced](https://www.youtube.com/watch?v=cl0MBeKDXLY) — Matt Cutts with Danny Sullivan, 2009-06
- [Penguin 4.0 keynote](https://www.youtube.com/watch?v=jGPkN4nKDyk) — Gary Illyes, PubCon Las Vegas, 2016-10
- [Nofollow, ugc and sponsored: the data](https://ahrefs.com/blog/nofollow-ugc-sponsored/) — Ahrefs, 2020
- [Search traffic study: pages without backlinks](https://ahrefs.com/blog/search-traffic-study/) — Ahrefs, 2023-12
- [Link rot study](https://ahrefs.com/blog/link-rot-study/) — Ahrefs, 2024-02
- [AI Overview brand visibility correlations](https://ahrefs.com/blog/ai-overview-brand-correlation/) — Ahrefs, 2025-05
- [AI Overviews and rankings overlap](https://www.seoclarity.net/research/aio-rankings-overlap) — seoClarity, 2025-10
- [When online content disappears](https://www.pewresearch.org/data-labs/2024/05/17/when-online-content-disappears/) — Pew Research Center, 2024-05-17
- [Internal links: a study of 23 million links](https://zyppy.com/seo/internal-links/seo-study/) — Zyppy, 2022
- [Selective link priority](https://zyppy.com/seo/selective-link-priority/) — Zyppy, 2023
- [Disavowing every link, again](https://zyppy.com/seo/google-disavow-experiment/) — Zyppy, 2024
- [Split test: nearby location links](https://www.searchpilot.com/resources/case-studies/seo-split-test-lessons-nearby-location-links) — SearchPilot, 2021
- [Long-term outgoing link experiment](https://www.rebootonline.com/blog/long-term-outgoing-link-experiment/) — Reboot Online, 2016
- [Google penalises its own Chrome page](https://techcrunch.com/2012/01/04/google-chrome-pagerank/) — TechCrunch, 2012-01-04
- [Content, shares and links: 1 million articles](https://moz.com/blog/content-shares-and-links-insights-from-analyzing-1-million-articles) — Moz and BuzzSumo, 2015
- [FTC’s Endorsement Guides](https://www.ftc.gov/business-guidance/resources/ftcs-endorsement-guides) — US Federal Trade Commission, 2023
- [Loi n° 2023-451 (influence commerciale), article 5-2](https://www.legifrance.gouv.fr/loda/article_lc/LEGIARTI000050457275) — Légifrance, 2024-11