As we wind down towards the end of 2018, many webmasters will be glad to see the back of the last 12 months given how busy Google has been making minor tweaks one moment then massive updates the next.

But which are this biggest most and most important Google algorithm changes from the last year? Let’s take a look.

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Mobile-First Index rollout – 26th March 2018

The long-awaited move to Mobile First Indexing was first announced by Google in November 2016, but it wasn’t until March of 2018 before the seismic change was rolled out:

Search engine land mobile first headline

What is Mobile First Indexing?

Google said that the steady shift in user behaviour, more searchers on mobile than desktop, has been the main catalyst for the change.

They explained that “crawling, indexing, and ranking systems have typically used the desktop version of a page’s content”. However, more users on mobile meant the previous way of evaluating the web “may cause issues for mobile searchers when that version is vastly different from the mobile version”

As a result, “mobile-first indexing means that we’ll use the mobile version of the page for indexing and ranking, to better help our – primarily mobile – users find what they’re looking for.”

Source – Rolling out mobile-first indexing

This huge change in how the web was being understood by Google cannot be overstated. Webmasters with unresponsive websites or poorly optimised mobile versions were hit hard.

Related: Mobile-First Index: What It Is & How Not To Be Affected

Mobile Speed Update – 9th July 2018

On the 9th of July, Google confirmed: “The Speed Update is now rolling out for all users”.

search engine roundtable mobile speed update

What is the Google Speed Update?

Google said the speed update “will only affect pages that deliver the slowest experience to users and will only affect a small percentage of queries.”

Source – Using page speed in mobile search ranking

With the move to a Mobile First Index back in March, it made a lot of sense for Google to now switch their focus to the mobile user experience, of which speed is a major factor.

For example, Think with Google revealed that 53% of mobile users will leave a page if it takes 3 seconds or more to load. In a Mobile First Indexing world, a slow website is no longer acceptable, and Google made that clear with this update.

Related: Why Is Pagespeed Important?

‘Medic’ Core Update – 1st August 2018

On 1st August, the Google Search Liaison Twitter account announced a “broad core algorithm update.”:

Google Search Liaison broad algorithm update tweet

What is the Medic Update?

Many believe this update relates to Google’s refocus on E-A-T (expertise, authority and trust) and YMYL (Your Money or Your Life) from within their Quality Rater Guidelines, which were updated a few days before the Medic update went live.

Related: A Guide to the Google E-A-T & YMYL Update

Who was affected?

This update seemed to severely affect sites in the health and wellness sectors:

Google Medic Update news headline

However, other potentially life-affecting verticals were also in the firing line, as seen below:

Verticals affected in the medic update

Source – Google’s August 1st Core Update: Week 1

Google has devalued several websites they feel are not the experts in life-altering areas. They never want to serve incorrect results with bad advice on important issues like finance and health.

This update had the biggest effect on visibility in 2018, with established websites like suffering huge ranking and traffic losses since August:

Affect of medic update on visibility graph

There have been a handful of smaller refreshes since the Medic update which have looked to scale back the initial August impact. These along with other less severe algorithm changes will be discussed next.

Other 2018 Google Updates

Google ‘Birthday Update’ – 27th September 2018

Nearly two months after the Medic Update, the algorithm tracking tools were experiencing higher than normal levels of activity.

There was substance to these fluctuations when a refresh was pushed out around Google’s 20th birthday:

Google birthday update headline in search engine land

This algorithm tweak was confirmed by Google’s own Danny Sullivan:

Danny Sullivan's tweet about the google birthday update

Source – Google Birthday Update

Many believe the birthday update altered the visibility of websites that were too harshly affected, either positively or negatively, following the August change.

A handful of reverberations was also felt in early October, which were likely additional tweaks to the Medic update:

Search engine roundtable october google update

Search engine roundtable october updates continued

Unnamed Core Updates – 17th April & 23rd May


Search engine tracking tools picked up heavy algorithm movement in the middle of April for several days.

Google would later confirm the fluctuations felt as a “core” update which they “routinely do throughout the year”. No name was given to this first Spring refresh:

Google algorithm update april headline


Google search liaison algorithm update april


A second unnamed update was felt in May, as yet again the industry tracking tools experienced higher than normal activity. Google never confirmed this update, but MozCast in particular saw unusually high temperatures over a 3-day period:

Algorithm temperature updates

SERP volatility after google algorithm update april

SERP fluctuation graph

Source – Is Another Google Update Happening In May?


2018 has been one of the most active algorithm years in recent memory.

With the move to Mobile First Indexing and the visibility swiping Medic Update, the last 12 months have left webmasters breathless.

It looks like the days of one major update every couple of years is now gone, with Google instead pushing out big core algorithm updates much more regularly.

If you have been affected by the 2018 algorithm changes or are unsure where to go next with your website in 2019, talk to us today!