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UPDATED: 18 Questions (and Answers) About Google, Site Speed, and SEO

June 11, 2014 — by Tammy Everts20

Ever since Google announced that page speed is a factor in its search ranking algorithm back in 2010, there has been rampant speculation as to how Google gathers performance data and how much SEO impact this data has. Google recently announced changes to Googlebot that some people speculate could pave the way for the web crawler to gather more nuanced performance metrics for the sites it crawls — and ultimately make performance a more critical ranking factor.


This seems like a good time to review and update our FAQ on Google, page speed, and search engine optimization.

1. Does the Google search bot track load time?

A lot of people assume that Googlebot measures page load, but no, the bot currently has nothing to do with measuring speed. Its main job is to discover new and updated pages to add to the Google index.

However, Google’s recent announcement might signal a shift. According to this post on the Google Webmaster Central Blog, the increasing complexity of modern web pages spurred the search team “to try to understand pages by executing JavaScript. It’s hard to do that at the scale of the current web, but we decided that it’s worth it. We have been gradually improving how we do this for some time. In the past few months, our indexing system has been rendering a substantial number of web pages more like an average user’s browser with JavaScript turned on.”

The capability for the indexing system to render pages similar to how the browser performs opens up some exciting new possibilities. I’ll be very interested to see what unfolds — and how much Google chooses to reveal.

2. Does Google use its PageSpeed tool to measure page speed for the purposes of search ranking?

Again, no. This is an understandably confusing question for many people, because PageSpeed is the name of a user-driven set of tools that let site owners analyze and optimize the performance of their pages. But these tools do not report back to Google for SEO purposes.

3. What about the Google Analytics Site Speed feature?

Prior to 2011, the answer to the question “Does Google use Google Analytics to help calculate search ranking?” was a resounding “No”.

In 2011, Google added a feature to Google Analytics that measures and reports real-world page speed to Analytics users who turn that feature on. Site Speed lets site owners know which of their pages are fastest and slowest, how page load time varies geographically, and how pages perform for different browsers. The launch of Site Speed led many to speculate that it would somehow be used for SEO purposes.

SEO and web performance: Google Analytics Site Speed is not a factor

You would think that all this data would be useful for factoring page speed into search ranking, but based on their silence on the subject, it would seem that Google still doesn’t use any of the data collected in Google Analytics for this purpose. In my opinion, they should, as it would allow them to sample more modern browsers.

4. Do they use the Speed Index?

No. The Speed Index is calculated by WebPagetest, a synthetic performance measurement tool that delivers results to the person conducting the test. Since Google uses the Google toolbar and onload metrics, and nothing synthetic (I’ll go into this in question 5), Speed Index is not a metric available to them.

While Speed Index isn’t involved in determining search ranking, it’s a great measurement, so I’m going to take this opportunity to digress for a moment and talk about it. Speed Index is a WebPagetest metric that attempts to give a more accurate measure of page load from a real user’s perspective. Below, you can see an example of what the Speed Index represents. I ran the Radware home page through WebPagetest, which gave the page a Speed Index score of 1484. This number roughly maps to 1.5 seconds. WebPagetest also generated a filmstrip view of the page load, and you can see that yes, the primary above-the-fold content begins to render just after 1.5 seconds.

Google, Page Speed and SEO: Speed Index

The Speed Index is a good step forward in performance measurement, because most measurement tools focus on metrics like start render and load time, both of which can paint a misleading picture of the actual user experience. Start render only represents when the first page resources begin to paint in the browser, and load time represents how long it takes for every resource to render, including third-party scripts and below-the-fold content, neither of which are relevant to understanding how the page performs for actual visitors.

5. So how DOES Google gather real-world performance data?

Google uses the Google toolbar to crowdsource data from real users. Here’s how they do it…

If you’ve installed the Google toolbar on your browser and you’ve activated the “PageRank checking” feature, then you’re helping Google measure load times for the purposes of search ranking. The toolbar measures the actual load time of every page you visit and sends the results back to Google. The results are then aggregated and used to determine real-world speed for each page.

Google toolbar

6. What browsers does the Google toolbar use?

The toolbar functionality is, as you would expect, already embedded in Chrome. The Google toolbar is also available as an add-on for Internet Explorer 6+. It used to be available for Firefox 2-4, but Google discontinued Firefox support in 2011.

7. What exactly does the Google toolbar measure?

It measures onLoad time: the time it takes for most, if not all, page resources to render in the browser — from resources you can see, such as text and images, to those you can’t see, such as third-party analytics. (“onLoad time” is also known as “document complete time” or “load time”.)

There’s a big caveat here: While onLoad time is an important measuring stick for performance, it needs to be taken with a grain of salt. It isn’t an indicator of when a page begins to be useful to the end user. A page with a onLoad time of 10 seconds can be almost fully interactive within 2 to 5 seconds. That’s because onLoad time can be inflated by third-party content, such as analytics scripts and tracking beacons, which users can’t even see.

Key takeaway: If your pages take a long time to get to onload, then according to Google they’re slow — even if they feel fast to your visitors. This is why we urge site owners to defer their third-party scripts, whenever possible, to load after the onLoad event.

8. Which pages does Google measure?

Google measures every page visited by users on your site.

9. What? Even pages I’ve marked as non-crawlable?

That’s right. Because the Google toolbar grabs all user-generated data via each participating user’s browser, it allows Google to measure all the pages your users see, not just what you have told Google is crawlable.

10. In terms of site traffic, at what point does the page speed factor kick in? Are we talking hundreds of thousands of page views per month? Millions?

This is a great question. Since I last updated this post, I’ve looked for an answer, but with no luck. It’s probably a good guess that with more page views, Google cares more, or that there’s a critical mass of page views after which speed is fully weighted in rankings, but that number is a mystery.

Something to bear in mind: If you subscribe to the widely held belief that page speed accounts for about 1% of the total algorithm weight, it might explain why sometimes speed doesn’t seem to affect ranking all that much, particularly on sites with relatively few page views.

11. What if my page is personalized and has very different content for authenticated users, but the same URL?

The Google toolbar makes no distinction between personalized content if the URL remains the same. All results are averaged together to determine the final score.

12. How will Google factor page speed into mobile search ranking?

A year ago, Google’s head of webspam, Matt Cutts, announced that Google would be rolling out a version of its site speed ranking factor for mobile sites. Matt did not specify a time frame, but many people feel that it’s been quietly rolling out in the year since Matt first made the announcement — particularly Google’s heavy promotion of its aspirational goal of sub-1-second load times for mobile devices.

Based on what we know about how Google gathers real user data via the Google toolbar for desktop, it’s safe to speculate that it could similarly gather mobile user data via its Google Search app. With upwards of 500 million installs on Android and iOS devices, this is a large enough user group to deliver statistically meaningful results.

13. Will preloading content on a page hurt my ranking?

Preloading is an advanced front-end optimization technique that we use in our FastView solution here at Radware. It lets our customers constantly track and analyze how visitors use their site. Then, using this information, it predicts what pages people are most likely to visit next and then pushes page resources to the visitor’s browser so they’re waiting on standby before the visitor even clicks.

Preloading is great because it gives the illusion of nigh-instantaneous page load, but site owners sometimes ask if it’s a trick that Google will reject and possibly even penalize them for. The short answer is no. As I’ve mentioned above, Google’s score is based on the onLoad time measurement. Preloading doesn’t cheat the system. It simply improves your onload time.

14. Will deferring page resources help my rankings?

Deferral is another excellent optimization technique. It allows you to defer non-essential page resources — such as third-party scripts — so that they load after the onLoad event. Deferral is an honest technique in Google’s books. Anything that helps a page improve its onLoad time will improve that page’s score.

15. Will a faster start render time help my rankings?

Start render time is different from onLoad time. As its name suggests, “start render” indicates when content begins to display in the user’s browser. While it can be measured, start render doesn’t indicate whether the first content to populate the browser is useful or simply ads and widgets. That happens somewhere between start render and onLoad.

Google, Page Speed, and SEO: onLoad

Start render time is a useful measurement because, over time, it gives good insight into the performance health of a page, but for our purposes in this post, start render time is meaningless, because Google focusing exclusively on onLoad time.

16. Are there any mobile-specific tactics I can use to help mobile search ranking for my site?

Last year Google also announced that they plan to roll out several ranking changes in the near future that address sites that are misconfigured for smartphone users. The announcement mentioned two common mobile configuration mistakes that site owners should be mindful of:

  • Faulty redirects — When a page redirects a user to a generic mobile-optimized page, rather than a mobile-optimized version of the specific page they were searching for.
  • Smartphone-only error — When mobile users are served an error page from search, instead of the page they were looking for.

After addressing these two issues, you can explore Google’s comprehensive list of recommendations for webmasters who want to optimize for mobile.

17. My site is already pretty fast. Is there a cutoff point at which making it faster won’t affect its SEO rank?

Pages that are already fast probably won’t experience a difference. If you’re taking your load time from 10 seconds down to 3 seconds, that’s a significant improvement that will likely help you. If you’re taking load times from 3 seconds to 1 second, you probably won’t see any real results.

You also have to consider how fast your pages are compared to the pages you’re competing against. If improving your load time makes you significantly faster than your competitors, you may notice a difference. If you were already faster than your competitors, not so much.

18. How much should I care about page speed?

The impact of page speed on SEO can range from negligible to very noticeable, depending on the site. I’ve read arguments that making pages faster did little to nothing to improve search ranking, and I’ve read case studies from companies that say they’ve made their pages faster and grown organic traffic anywhere between 20 percent and 40 percent.

I stand by what I’ve always said: regardless of how great a ranking factor site speed is, you should care about how fast your pages are. SEO is just one benefit of serving faster pages. Our customers also report dramatic increases in metrics like revenue, conversions, page views, customer retention, and application adoption.

In other words, if you care about the entire end-to-end user experience — from your visitors being able to find your site quickly to being able to navigate and complete whatever tasks they need to complete — then you should care about speed.

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Tammy Everts

As a former senior researcher, writer, and solution evangelist for Radware, Tammy Everts spent years researching the technical, business, and human factor sides of web/application performance. Before joining Radware, Tammy shared her research findings through countless blog posts, presentations, case studies, whitepapers, articles, reports, and infographics for Strangeloop Networks.

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