All the Google Algorithm Updates That Mattered in 2021

Google algorithm updates were the big SEO trend of 2021 with one of the busiest update roadmaps we’ve seen in recent years. Aside from the pre-announced page experience update and the usual core updates expected every year, Google hit us with a string of surprises and the summer period, in particular, was one of the most volatile we’ve seen.

In this article, we take a look at all of the algorithm updates that mattered in 2021, summarise the key takeaways from each of them and analyse what they mean for search marketing in 2022.

2021 was a busy year for algorithm updates

As we explain in our recent biggest SEO challenges article, Google hit us with a lot of algorithm updates this year and the summer period was particularly intense. At one point we had three updates in the space of one month and half a dozen over a three-month period, rolling out almost back-to-back.

As always, some updates make more of an impact than others and there are always winners and losers from one update to the next.

However, when you look at the collective impact of this year’s heavy update schedule, it’s had a significant impact on ranking volatility. Back in October, Head of Communications at Semrush, Mordy Oberstein, published data from the Semrush Sensor tool showing how volatility in the SERPs has increased this year.

The frequency of updates this year has also made it difficult to analyse each one in isolation. Normally, we have weeks or months to attribute ranking changes to major algorithm updates and identify which signals are affected by each one.

This year, the busy update schedule and the back-to-back rollout during the summer, in particular, made it harder to attribute changes to specific updates.

With that in mind, let’s take a look at all of the algorithm updates from 2021 and explain what we know (and don’t know) about them.

The complete list of 2021 Google algorithm updates

This year, we’ve had 10 algorithm updates announced and/or confirmed by Google. Every year, there are an unknown number of unconfirmed updates, most of which have a moderate impact on rankings or such a small impact they’re barely distinguishable from regular movement in the SERPs.

However, this year, three unconfirmed updates each had a major impact on results so we’re including all 10 confirmed updates and the three unconfirmed that shook things up this year:

  1. Passage indexing (Feb 10): Google starts ranking passages from web pages for very specific queries, affecting 7% of searches worldwide.
  2. *Featured Snippet drop (19 Feb): A 40% drop in Featured Snippet impressions with YMYL pages being hit hardest.
  3. *Featured snippet recovery (12 Mar): A complete (or close to it) recovery from the Featured Snippet drop three weeks earlier.
  4. Product reviews update (8 Apr): Google rewards in-depth product reviews while thin or overly promotional reviews (affiliate links) suffered.
  5. June 2021 Core Update (2 Jun): Google announces the first core update of 2021 and pre-announces a second update for the next month.
  6. Spam updates (23 Jun & 28 Jun): Google releases two spam updates less than a week apart.
  7. Page experience update (25 Jun): After several delays, Google officially rolls out the page experience update.
  8. MUM (Jun): Google implements its new Multitask Unified Model (MUM) technology at an unspecified date in June.
  9. July 2021 Core Update (1 Jul): The follow-up to the June 2021 Core Update.
  10. Link spam update (28 Jul): Google rolls out a broad link spam update across languages over a four-week period.
  11. Page title rewrites (16 Aug): SEOs report a dramatic increase in Google rewriting page titles in the SERPs, later confirmed as an update by Google’s Danny Sullivan.
  12. *Unconfirmed update (2 Oct): Heavy movement in the SERPs for several days but no word from Google on any algorithm updates.
  13. Spam update (3 Nov): Google announces its fourth spam update of the year, which rolls out over 7-8 days.

Now, let’s take a look at each of these updates and what has changed for search marketers this year.

#1: Passage indexing – 10 February

The first algorithm update of 2021 landed on 10 February, commonly referred to as passage indexing although passage ranking is probably a more suitable description. The update didn’t have a major impact on ranking positions and it was more of a new feature introduction than the kind of algorithm update we’re used to seeing from Google.

That said, the new feature does change how Google’s algorithm indexes and ranks content.

Passage ranking is an AI-powered update designed to help Google return the best result for “very specific” searches. Essentially, the update allows Google to rank a passage that specifically addresses the user’s search query, even if the page itself is optimised for a different keyword.

For example, let’s say you have an in-depth blog post covering a broad topic, such as buying a second-hand car. Your primary keywords will be things like “buying a second-hand car,” “how to buy a second-hand car” and “what to check when buying a second-hand car”.

Your page title, headings and content will be optimised for keywords like this but your guide may include a section on the common financing options available to people buying used vehicles from a dealer.

Now, someone searching for information on the differences between Hire Purchase (HP) and Personal Contract Purchase (PCP) financing options may see your buying guide because Google understands the intent of their specific query and your comparison provides the best answer to their question, even if other posts are better optimised for the query.

Here’s what Google has to say about the update:

“Very specific searches can be the hardest to get right, since sometimes the single sentence that answers your question might be buried deep in a web page. We’ve recently made a breakthrough in ranking and are now able to better understand the relevancy of specific passages. By understanding passages in addition to the relevancy of the overall page, we can find that needle-in-a-haystack information you’re looking for.”

Google says passage indexing (or ranking) will affect seven percent of search queries across all languages as it rolls out gradually. This began in the US for English results on 10 February and continues to roll out globally.

#2: Featured Snippet drop – 19 February

On 19 February, MozCast reported a 40% decline in visibility for Featured Snippets, which plummeted to their lowest point since 2015. In many cases, Featured Snippets disappeared altogether and the impact was especially hard on health and finance queries.

Moz’s Dr. Peter J. Meyers published a blog post covering Featured Snippet visibility from February 10-23 with no signs of recovery.

featured-snippets-search-visibility-drop All the Google Algorithm Updates That Mattered in 2021


Delving into the data, Meyers saw that health queries experienced the biggest decline with a -68% drop in Featured Snippets while finance came in at a close second with a -60% decline.

featured-snippets-losers All the Google Algorithm Updates That Mattered in 2021


It turned out the biggest drops were seen for short queries, particularly single-word queries, and pages considered as YMYL were hit hardest (this explains the heavy hit on health and finance).

The key takeaway? Make sure you’re up-to-date with the latest on E-A-T and YMYL and update your content to meet Google’s expectations, especially if your pages qualify as YMYL.

#3: Featured Snippet recovery – 12 March

Precisely three weeks after 40% of featured snippets mysteriously disappeared from Google Search, they miraculously reappeared on 12 March with the same ranking positions as before.

To this day, Google has given no explanation for the disappearance or reappearance of Featured Snippets nor confirmed whether the episode was the result of an algorithm update gone wrong, a bug or anything else.

The closest thing we got to an explanation was general commentary from Google’s John Mueller who was careful enough not to reference the sudden drop and reappearance in February and March:

“I don’t know. …The featured snippets and rich results in general, those kinds of things can fluctuate over time.

And I know the teams are always working on those features and trying to fine-tune the triggering.

So when we would show them or when we wouldn’t show them, sometimes the triggering changes over time that we just kind of reduce the threshold overall or that we change the focus a little bit and say like less here and more here. Sometimes that happens across geographies or languages.

But these kinds of changes from our side are essentially normal organic changes in search, how they can always happen.”

That’s a typically diplomatic response from John Mueller but the Featured Snippet disappearing trick was anything but “normal organic changes”.

#4: Product reviews update – 8 April

On 8 April, Google announced an update specifically targeting product review content. After a testing, experimentation and review process, Google determined that a lot of review content doesn’t deliver information that truly helps people make purchase decisions.

Here’s what Google said in its announcement.

“From this, we know people appreciate product reviews that share in-depth research, rather than thin content that simply summarizes a bunch of products. That’s why we’re sharing an improvement to our ranking systems, which we call the product reviews update, that’s designed to better reward such content.

This update is going out today and only involves English language reviews for now. We believe this will further help those producing rich content in the product reviews area.”

To bring review content up to its new expectations, Google provided a list of questions you should ask before publishing and updating any reviews on your website.

Do your reviews:

  • Express expert knowledge about products where appropriate?
  • Show what the product is like physically, or how it is used, with unique content beyond what’s provided by the manufacturer?
  • Provide quantitative measurements about how a product measures up in various categories of performance?
  • Explain what sets a product apart from its competitors?
  • Cover comparable products to consider, or explain which products might be best for certain uses or circumstances?
  • Discuss the benefits and drawbacks of a particular product, based on research into it?
  • Describe how a product has evolved from previous models or releases to provide improvements, address issues, or otherwise help users in making a purchase decision?
  • Identify key decision-making factors for the product’s category and how the product performs in those areas? For example, a car review might determine that fuel economy, safety, and handling are key decision-making factors and rate performance in those areas.
  • Describe key choices in how a product has been designed and their effect on the users beyond what the manufacturer says?

Google clarified that the product reviews update was not a core algorithm update but it did state that Google’s usual advice for core updates did apply. We can’t confirm what Google meant by that but we expect it relates to content quality and the increased importance of E-A-T and YMYL.

For example, product reviews should be written by someone with proven experience and expertise on the product categories in question with their author bio and relevant links included in every post. For example, laptop reviews should be written by experienced tech reviewers who know their stuff, can go into detail and genuinely help people choose one device over the other options available to them.

Mordy Oberstein published a great writeup of the update’s winners and losers on Search Engine Journal, showcasing how the update was more complex than simply targeting thin content or affiliate links.

The big winners were pages that include buyer’s guides, comparison tables and calculations to help shoppers choose the ideal product for their needs. Affiliate content disguised as product reviews has suffered the most and Google is a lot more capable of detecting this type of content now.

#5: June 2021 Core Update – 2 June

On 2 June, Google took the surprising step of announcing not one, but two core algorithm updates – one rolling out later in the day and another in the following month. The reason for the double update was simple enough: “Some of our planned improvements for the June 2021 update aren’t quite ready, so we’re moving ahead with the parts that are, then we will follow with the rest with the July 2021 update”.

Once again, websites with thin content lost out from the first update and YMYL pages suffered more than most – not for the first time in recent years. That being said, some of the winners from the June 2021 Core Update were losers from previous core updates and this was another reminder that updates themselves are experimental and Google is willing to correct itself when it takes things too far.

The June 2021 Core Update also kicked off the busy summer of updates – some of which we knew about, many we didn’t.

#6: Spam updates – 23 June & 28 June

The next summer surprise from Google was a spam update announced on 23 June via Twitter. Once again, Google told us that another spam update would follow, this time during the next week.

Google pointed towards an updated list of webmaster guidelines ahead of the first update, including general guidelines and quality guidelines for website owners.

Above all, you should avoid all of the following:

  • Automatically generated content
  • Participating in link schemes
  • Creating pages with little or no original content
  • Cloaking
  • Sneaky redirects
  • Hidden text or links
  • Doorway pages
  • Scraped content
  • Participating in affiliate programs without adding sufficient value
  • Loading pages with irrelevant keywords
  • Creating pages with malicious behaviour, such as phishing or installing viruses, trojans, or other badware
  • Abusing structured data markup
  • Sending automated queries to Google

You should also monitor your website for hacking and take steps to prevent and remove user-generated spam on your site. This will become increasingly important as attacks against websites and spam techniques continue to become more sophisticated.

#7: Page experience update – 25 June

Google announced the page experience signal in June 2020, giving us plenty of time to prepare for the update on 25 June, 2021. The update combined several existing signals related to user experience with the newer Core Web Vitals signals that measure loading times, the responsiveness of interactive elements and the visual stability of pages.

google-page-experience-signals All the Google Algorithm Updates That Mattered in 2021

The cumulative page experience signal combines these independent signals into a single measurement for Google’s algorithm, allowing it to grade the overall quality of user experiences on individual pages.

Currently, there are three Core Web Vitals included in the page experience signal although Google says it may expand upon these over time:

  1. Loading: This simply refers to loading times although Google is changing the way it measures this with a new standard called Largest Contentful Paint (LCP).
  2. Interactivity: Measures the responsiveness of interactive elements on your page (links, buttons, etc.) after users click them, using a new standard called First Input Delay (FID).
  3. Visual Stability: Detects the movement of elements after they’ve loaded on the page and any instability this causes, using a new standard called Cumulative Layout Shift (CLS).

Google initially suggested the impact of the page experience update could be mild, stating that quality is the determining factor in rankings. It said the page experience signal could help differentiate between two pages of similar quality.

It turns out, Google may have done a better job of playing down the update than it intended and Danny Sullivan later insisted that it could have a bigger impact over time, even if the overnight effects were small.

Of course, ranking signals aren’t the only reason you need to provide a positive user experience and the Core Web Vitals aspect of the page experience update shows Google is taking UX more seriously.

Take a look at our guide on optimising for Core Web Vitals and the page experience signal for more information.

Currently, the page experience signal only applies to mobile pages but Google’s Jeffrey Jose says it will be applied to the desktop ranking system in February 2022.

#8: Multitask Unified Model (MUM) – June

Google rolled out its Multitask Unified Model (MUM) on an unspecified date in June 2021 and the busy summer of updates makes it difficult to pinpoint a date. Technically, the passage indexing update rolled out in February is a part of MUM so this could be counted as an extension or the completion of a much larger update or the start of an update that could take months or years to make its full impact.

google-mum-technology All the Google Algorithm Updates That Mattered in 2021

MUM replaces BERT and Google says the new technology is 1,000x more powerful than its predecessor, allowing the search engine to understand complex queries to a greater degree. MUM also allows Google to multitask more effectively, pulling in content from multiple languages and translating it into the source language of the original query.

Much like BERT, it could take several years for the new technology to mature and have a major impact on the SERPs but Google is already teasing a new search experience, powered by the AI technology for 2022.

#9: July 2021 Core Update – 1 July

Google didn’t hang around with the July 2021 Core Update, rolling it out on the first day of the month. The follow-up to the June 2021 Core Update had a smaller overall impact but it hit harder and faster than the gradual rollout of the first update, peaking on 1 July and showing intense fluctuations in the following days.

Semrush-report-google-july-core-update-effect All the Google Algorithm Updates That Mattered in 2021

The Semrush Sensor tool showed volatility was 42% more dramatic than the first core update of the summer.[1]

As with all core updates, it’s difficult to pinpoint the signals being affected and Google pushes the message that you can’t optimise for core algorithm updates. If you experience a decline in traffic from one core update, you’ll also often experience some kind of recovery during the next one or, in the worst cases a double hit if you’ve got serious issues with your pages.

You can read Google’s take on this Search Central blog post.

#10: Link spam update – 26 July

On July 26, Google announced a link spam update that would roll out over the coming two weeks but, ultimately, took a full month to finish rolling out. Search Quality Analyst at Google, Duy Nguyen, said that although “link spam has been greatly reduced over the past two decades, thanks to our constant improvements in our ranking systems and spam detection systems.”

“This algorithm update… is even more effective at identifying and nullifying link spam more broadly, across multiple languages. Sites taking part in link spam will see changes in Search as those links are re-assessed by our algorithms.” – Duy Nguyen, Search Quality Analyst at Google

The update didn’t penalise sites for spammy links but nullified any ranking benefits so sites with major issues in their link profiles could experience ranking hits that felt a lot like a penalty.

If your site experienced a heavy hit during this period, the only course of action you could take is to analyse your link profile and identify drops in traffic with suspect inbound or outbound links.

To prevent any nasty surprises with updates like this (or link penalties), run regular link audits to identify low-quality or potentially harmful links in your profile. Remove anything that looks suspicious and follow Google’s guidelines to protect yourself from future link spam updates.

#11: Page title rewrites – 16 August

In mid-August, SEOs started reporting a significant increase in Google rewriting page titles in the SERPs. While Google often adapts page titles to make them more relevant to user queries, the frequency and extent of changes being reported in the second half of August were extreme – and, at times, erroneous.

On 24 August, Google confirmed an algorithm update that adapted the search engines process for generating web page titles in SERP results.

“Last week, we introduced a new system of generating titles for web pages. Before this, titles might change based on the query issued. This generally will no longer happen with our new system. This is because we think our new system is producing titles that work better for documents overall, to describe what they are about, regardless of the particular query.” – Danny Sullivan, Search Liaison at Google

Regardless, the chatter from SEOs on social media suggested most were unhappy about losing further control over how their page titles show in search. On 27 September, Google updated its announcement of the update, thanking SEOs for the feedback and confirming that further changes had been made to the new system.

As a result, the frequency and degree of changes to page titles calmed from their peak in mind-August but Google still has more power over your page titles than before the update. Google insists that a “focus on good HTML title tags” is still important and published new guidelines for website owners on the Search Central website.

#12: Unconfirmed update – 2 October

Over the weekend of 2-3 October, SEOs and reporting tools signalled major volatility in the SERPs with the kind of fluctuations you would normally expect from a core update. With no announcement from Google and no confirmation after widespread reports of volatility, this one has to go down as an unconfirmed update.

These happen all the time but they’re not always significant and rarely comparable to core algorithm updates.

One explanation is that the volatility could have been a correction from one of this year’s core updates or some of the feature testing Google has performed throughout the year. Aside from that, we can only speculate, especially with the frequency of updates during the summer months making it more difficult to analyse movement in the SERPs.

#13: November 2021 spam update – 3 November

On November 3, Google announced another spam update, the fourth one rolled out this year.

While this update was significant, it only affected websites clearly involved in spam or compromised by hacks. As long as you’re following Google’s webmaster guidelines and running the essential security measures, you shouldn’t run into any problems with updates like these.

That being said, it’s worth noting that Google has taken a big stand against spam with four updates this year.

What does all this mean for SEO?

This big question heading into 2022 is whether the busy schedule of updates this year was a one-off or the new normal for SEOs. We know that Google delayed at least one algorithm update in 2020 due to the pandemic so perhaps this year’s hectic schedule was simply the result of several updates being squeezed into 2021.

That said, we also know Google has teased significant changes to the search experience for 2022 and these changes are powered by its new Multitask Unified Model (MUM) technology, which is expected to expand in a similar fashion to BERT before it.

The good news is, we don’t have any major pre-announced updates for next year, as we’ve had in the past with the page experience, mobile-friendly and other updates. However, there is another “but” in the sense that the page experience signal will be applied to desktop ranking in February 2022.

As we discussed earlier, Danny Sullivan has also hinted that the page experience update could have an increased impact over time so we may start to see more influence in 2022.

The big issue for search marketers is that it’s been even more difficult to analyse updates in 2021 due to the busy schedule and overlap of updates this year, especially during the summer months where updates were sandwiched by others.

Here’s a summary of what we do know from the updates in 2021:

  • Passage indexing/ranking means passages can rank for queries from pages that are optimised for other keywords.
  • Product review content should help users choose the right product for their needs, based on specs, price and other comparisons.
  • Page experience could gradually have a stronger impact than we’ve seen so far.
  • Google is rewriting page titles more often and to a greater extent.
  • MUM will make a stronger impact on the search experience and the SERPs over the coming years.
  • YMYL pages suffered more than most during updates in 2021 often experiencing the strongest drops but also partial recoveries, suggesting Google hasn’t finished adapting its algorithm for these pages.


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