STATE OF THE UNION. Ecommerce Page Speed & Web Performance Fall 2013 SHARE THIS WHITEPAPER

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1 Ecommerce Page Speed & Web Performance Fall 2013 SHARE THIS WHITEPAPER

2 Table of Contents Executive Summary... 3 Why Test Leading Ecommerce Sites?... 3 Key Findings... 3 Who Was Fastest?... 4 The 10 Fastest Sites (Time to Interact)... 4 The 10 Fastest Sites (Load Time)... 5 Finding #1: The Trend Toward Bigger, Slower Pages Continues... 5 Why Does Page Size Matter?... 5 Finding #2: Median Time to Interact Is 5.3 Seconds... 6 Why Should Pages Be Interactive in 3 Seconds or Less?... 6 Finding #3: Three Common Design Best Practices Are Failing Users (and Site Owners) Feature Banner Loads Last Feature Banner Loads Last with Call-to-Action at the Bottom Feature Banner Loads Last with No Call-to-Action... 7 Finding #4: Adoption of Performance Best Practices Is Inconsistent... 8 Use a Content Delivery Network... 8 Enable Keep-Alives... 8 Compress Images... 8 Progressive JPEGs... 9 Why Are Some Best Practices Thriving While Others Struggle?... 9 Finding #5: Browser Vendors Are Not Keeping Pace with Page Demands Slow Pages? Don t Blame Your Browser There s No Such Thing As a One-Size-Fits-All Solution Things Site Owners Can Do to Fix Their Performance Pains Consolidate JavaScript and CSS Sprite Images Compress Text and Images Defer Rendering Below the Fold Content Ensure That Feature Images Are Optimized to Load Early and Quickly Rethink the Design and Location of Call-to-Action Links in Feature Graphics Reformat Images Use Progressive JPEGs Minify Code Defer Loading and Executing Non-Essential Scripts Use AJAX for Progressive Enhancement Use a Content Delivery Network Takeaways About Radware Sources Smart Network. Smart Business. 2

3 Executive Summary Within the past two years, web page speed has migrated from the fringe to center stage, emerging as not just a technology trend, but a hot-button business issue. Coverage by The New York Times 1 and CNBC 2 has resulted in web performance becoming a familiar phrase within the online community. Yet the question remains: what impact, if any, has the mainstreamification of web performance had on the websites that many of us use every day. Certainly there are compelling arguments for why companies particularly online retailers should care about serving their pages faster to their users. Numerous studies have found an irrefutable connection between load times and key performance indicators. In one twelve-week study into the impact of page delays on ecommerce metrics, it was found that a mere one-second delay resulted in the following penalties: 3.5% decrease in conversion rate, 2.1% drop in cart size, 9.4% fewer page views, and 8.3% increase in bounce rate. 3 On a more positive note, an internal Walmart.com study found that for every one second of load time improvement, the site experienced up to a 2% increase in conversions. For every 100 milliseconds of improvement, incremental revenues grew by up to 1%. 4 Why Test Leading Ecommerce Sites? Since 2010, we have been measuring and tracking the performance and page composition of leading ecommerce sites. The purpose of this research is to gain ongoing visibility into the real-world performance of leading ecommerce sites to learn how these sites perform for visitors sitting at home using the internet under normal browsing conditions and to provide strategies and best practices that will enable site owners to serve pages faster. The goal of this report is to answer the following questions: Given the assumption that page speed is an increasingly urgent issue for online retailers, has this urgency translated into faster pages over time? How do pages actually render in real-world scenarios? How quickly have retailers moved to adopt core performance best practices, such as using content delivery networks (CDNs)? How do different browsers compare in terms of page rendering speed? Our findings are detailed in this report, and are summarized here: Key Findings 1. The trend toward bigger, slower pages continues. The median page took 8.56 seconds to load for first-time visitors. This represents a 14% slowdown over the median of 7.48 seconds recorded three months ago, in our Summer 2013 report. The median page is currently 1258 KB and contains 92 resources (images, JavaScript, CSS files, etc.). Smart Network. Smart Business. 3

4 2. The median page takes 5.3 seconds to become interactive. This represents an 8% slowdown since Summer 2013, when the median time to interact (TTI) was 4.9 seconds. Ideally, pages should be interactive in 3 seconds or less. 3. Three common design practices are failing users. Most sites made one of three critical mistakes in the design and presentation of their feature content. 4. The adoption of performance best practices is inconsistent, even among leading sites. Among the top 100 sites, adoption of some best practices is nearing the saturation point, whereas others remain neglected. 5. Browser vendors are not keeping pace with page demands. Across all three major browsers, performance is trending downward as browser vendors struggle to keep pace with the demands of today s large, complex, dynamic web pages. Except where otherwise noted, the results discussed in this report are for pages tested in Chrome 29. At the time of conducting this research, Chrome was the most widely used browser in the United States, with a market share of 34%. 5 Who Was Fastest? All page load times are indicated in seconds. The 10 Fastest Sites (Time to Interact) Among the top 100 sites, these were the fastest in terms of their ability to display meaningful, interactive content (e.g., feature banners with functional call-to-action buttons). This metric is otherwise known as time to interact (TTI). We have provided the TTI alongside the full load time in order to give perspective into the distinction between the two, and to illustrate that load time is not always the most meaningful measure of a site s performance. For example, Autotrader.com has a load time of 12.3 seconds, but a TTI of 2.2 seconds; the TTI indicates that this site delivers a satisfying user experience. 1s 2s 3s 4s 5s 6s Abebooks.com Amazon.com CDUniverse.com Autos.yahoo.com Ikea.com BHphotovideo.com iherb.com Carmax.com Autotrader.com Trademe.co.nz 1.2s TTI 2.0s TLT 1.4s TTI 1.4s TTI 1.7s TTI 1.8s TTI 2.8s TLT 3.3s TLT 2.0s TLT 2.1s TTI 2.7s TLT 2.1s TTI 2.1s TTI 2.2s TTI 2.2s TTI 4.1s TLT 4.6s TLT 5.1s TLT 12.3s TLT 9.7s TLT TTI - Time to Interact TLT - Total Load Time Smart Network. Smart Business. 4

5 The 10 Fastest Sites (Load Time) Among the top 100 sites, these were the 10 fastest in terms of the time required for all page elements to load. It is worth noting that 38% of the Alexa Retail 500 took 10 seconds or longer to load. Abebooks.com BHphotovideo.com CDUniverse.com Amazon.co.uk Target.com Ikea.com Nordstrom.com Amazon.com Wiley.com Forever21.com 2.0s 2.0s 2.5s 2.7s 2.8s 3.3s 3.6s 3.9s 4.0s 4.1s Finding #1: The Trend Toward Bigger, Slower Pages Continues. The median page took 8.56 seconds to load for firsttime visitors. This represents a 14% slowdown over the median recorded just three months ago, in our Summer 2013 report. Looking at the current size and composition of the median page, it is easy to note one of the causes of this page slowdown: web pages are getting bigger and more complex. The median page is currently 1258 KB and contains 92 resources (images, JavaScript, CSS files, etc.). This represents 15% growth since Summer 2013, when the median page was 1095 KB and contained 89 resources. 8.56s Now 7.48s Summer s Fall 2012 Why Does Page Size Matter? For most sites, one of the greatest performance drains is the need to complete dozens of network round-trips to retrieve resources such as style sheets, scripts, and images. Each of these resources makes an individual round trip from the user s browser, which requests the file from the host server, which in turn delivers the file to the browser. Each round trip can take between 65 and 145 milliseconds (or longer) for desktop browsers numbers that add up quickly when a typical page contains almost 100 resources Smart Network. Smart Business. 5

6 Finding #2: Median Time to Interact Is 5.3 Seconds. Time to interact (TTI) is the point at which a page displays its primary interactive content (e.g., feature banners with functional call-to-action buttons). TTI is a crucial indicator of a page s ability both to deliver a satisfactory user experience (by delivering content that the user is most likely to care about) and to fulfill the site owner s objective (by allowing the user to engage with the page and perform whatever call to action the site owner has deemed the key action for that page). In measuring the time to interact for the top 100 ecommerce sites, we found the following: 5.3s median TTI The median TTI was 5.3 seconds. This represents an 8% slowdown since Summer 2013, when the median TTI was 4.9 seconds. Only 18% of the top 100 sites had a TTI of 3 seconds or less. 26% of the top 100 sites took 8 or more seconds to become interactive. 8% slowdown since Summer 2013, when the median TTI was 4.9 seconds 20s 26% 15s 10s 5s 18% 0s Only 18% of pages became interactive in 3 seconds or less. 26% took 8 seconds or more to become interactive. Why Should Pages Be Interactive in 3 Seconds or Less? Separate studies have found that: 57% of consumers will abandon a page that takes longer than 3 seconds to load. 6 A site that loads in 3 seconds experiences 22% fewer page views, a 50% higher bounce rate, and 22% fewer conversions than a site that loads in 1 second, while a site that loads in 5 seconds experiences 35% fewer page views, a 105% higher bounce rate, and 38% fewer conversions. 7 Finding #3: Three Common Design Best Practices Are Failing Users (and Site Owners). As part of the testing process, we generated filmstrip views of the entire median page load for each of the top 100 home pages. In addition to measuring the time to interact (TTI) discussed earlier in this report, this frame-by-frame view also enabled a heuristic design evaluation that resulted in the discovery of three pervasive usability issues: 6

7 STATE OF THE UNION 1. Feature Banner Loads Last. This was the most common design failure. Site owners should be aware of the usability consequence of delaying the rendering of feature content: a user who endures an 8-second download delay spends only 1% of their total viewing time looking at the featured space on a page. In contrast, a user who receives instantaneous page rendering spends 20% of their viewing time within the feature area of a page.8 2. Feature Banner Loads Last with Call-to-Action at the Bottom. Placing the call to action (CTA) at the bottom of feature banners is a widely followed design convention, yet it frequently poses a significant performance penalty. In many of the pages we studied, it was noted that the CTA arguably the most critical page element was often the last visible element to render. 3. Feature Banner Loads Last with No Call-to-Action. We also noted instances in which the feature banner required considerable render time, and it was not until the image had fully rendered that it became clear that there was no CTA. This presents a compounded usability issue: first, the slow render time, followed by disruption of the user s expectation that the wait time will result in a clear call to action. Smart Network. Smart Business. 7

8 Finding #4: Adoption of Performance Best Practices Is Inconsistent. Site owners who neglect core performance best practices may be missing out on opportunities to make relatively easy performance gains. Among the top 100 sites, adoption of some best practices is nearing the saturation point, whereas others are still neglected. (Letter grades refer to the Google Page Speed scores for each technique.) Use a Content Delivery Network Using a content delivery network (CDN) can reduce load time by up to 30%. 79% of sites currently use a CDN to cache resources closer to end users, thereby shortening server round trip time. ENABLE KEEP-ALIVES A 93% B 6% C 1% USE A CONTENT DELIVERY NETWORK (CDN) NO 21% YES 79% Enable Keep-Alives Enabling keep-alives is a performance technique that allows site owners to control how many times the TCP (transmission control protocol) connection takes place. TCP connection is the process by which both the user and the server send and receive acknowledgment that a connection has been made and that data can begin to be transferred. Too many TCP connections will slow down a site. Currently, 100% of the sites we tested have keep-alives enabled on their sites, though 7% of these sites did not score an A. Compress Images Images comprise the bulk of a typical page s total size, and much of this bulk is unnecessary caused by poorly optimized or unoptimized images. Image compression is a core performance best practice that allows site owners to reduce this payload; however, of the top 100 sites we tested, 45% failed to compress images, with only 9% scoring an A grade. Smart Network. Smart Business. 8 B 12% C 20% A 9% JPEG COMPRESS IMAGES D 14% F 45%

9 Progressive JPEGs There are two types of JPEGs: baseline and progressive. A baseline JPEG is a full-resolution image that loads in a single top-to-bottom scan. A progressive JPEG is an image that loads in a series of scans, beginning with a low-resolution image and progressing at increasing resolutions until the full resolution is achieved. In many cases, progressive JPEGs improve perceived load time because the user receives visual feedback earlier than with a baseline JPEG. Only 6% of the sites we tested use progressive JPEGs on their pages, with 87% failing to use progressive JPEGs. (7% of sites returned null results.) JPEG 6% - Yes 7% - N/A 87% - No Why Are Some Best Practices Thriving While Others Struggle? It is critical to note that two of the most widely adopted techniques use a CDN and enable keep-alives both fall outside the web developers domain. For most site owners, content delivery is outsourced to third parties, while enabling keep-alives is a server/load balancer configuration task. While best practices such as using a CDN and enabling keep-alives approach the saturation point among leading sites, it is concerning that fundamental techniques such as image compression and progressive JPEGs are not more widely adopted. This poor adoption rate among developers could be attributed to a number of factors: lack of performance education, lack of resources dedicated to ongoing performance optimization, lack of investment in front-end optimization tools that automate the implementation of these practices, and/or lack of developer control over page resources (e.g. due to content management systems). Whatever the cause, the takeaway is that many site owners are missing out on the opportunity to exploit a number of techniques that have the potential to dramatically improve the user experience. Google Page Speed Score Legend Google Page Speed assigns sites a score out of 100 for each best practice it measures. A: B: C: D: F: 0-59 Smart Network. Smart Business. 9

10 Finding #5: Browser Vendors Are Not Keeping Pace with Page Demands. Across all three major browsers, performance is trending downward as browser vendors struggle to keep pace with the demands of today s large, complex, dynamic web pages. Spring 2013 Summer 2013 Fall s 8s 9s FIREFOX 22 Spring s Summer s Fall s INTERNET EXPLORER 10 Spring s Summer s Fall s CHROME 29 Spring s Summer s Fall s Slow Pages? Don t Blame Your Browser. When it comes to performance, browser vendors frequently receive the brunt of users ire; however, it is important to credit browser developers and their ongoing focus on performance as a feature for their role in mitigating the impact of the rampant increase in page size and complexity cited elsewhere in this report. There s No Such Thing As a One-Size-Fits-All Solution. Site owners should be aware that, while modern browsers are more or less equal in terms of their ability to render pages, all browsers are not the same. Each browser has its own unique preferences in terms of how it renders pages: e.g., a page that is optimized for Chrome may not perform as well in Firefox. Site owners should educate themselves about these preferences and develop their pages accordingly. The W3C offers guidelines for optimizing content for different browsers. 9 Note: Our tests simulated load time for a user viewing a single site within the browser. Our tests did not cover other common scenarios that can affect performance, such as the following: 1. Browser performance under stress from having multiple tabs or windows open simultaneously. 2. Browser performance degradation over time (e.g., the longer the browser remains open, its likelihood of crashing). 3. Browser performance when visiting sites that use HTML5 or Flash, or when watching videos. 4. Usability. This comes down to personal preference. For example, while some users may prefer a more minimal look and feel, others might value the functionality of add-on features. Smart Network. Smart Business. 10

11 12 Things Site Owners Can Do to Fix Their Performance Pains There are a number of best practices site owners can implement in order to improve both the real and perceived user experience for online shoppers. 1. Consolidate JavaScript and CSS. Consolidating JavaScript code and CSS styles into common files that can be shared across multiple pages should be a common practice. This technique simplifies code maintenance and improves the efficiency of client-side caching. In JavaScript files, be sure that the same script isn t downloaded multiple times for one page. Redundant script downloads are especially likely when large teams or multiple teams collaborate on page development. 2. Sprite Images. Spriting is a CSS technique for consolidating images. Sprites are simply multiple images combined into a rectilinear grid in one large image. The page fetches the large image all at once as a single CSS background image and then uses CSS background positioning to display the individual component images as needed on the page. This reduces multiple requests to only one, significantly improving performance. 3. Compress Text and Images. Compression technologies such as gzip reduce payloads at the slight cost of adding processing steps to compress on the server and decompress in the browser. These operations are highly optimized, however, and tests show that the overall effect is a net improvement in performance. Text-based responses, including HTML, XML, JSON (JavaScript Object Notation), JavaScript, and CSS, can all be reduced in size by as much as 70%. 4. Defer Rendering Below the Fold Content. Assure that the user sees the page quicker by delaying the loading and rendering of any content that is below the initially visible area, sometimes called below the fold. To eliminate the need to reflow content after the remainder of the page is loaded, replace images initially with placeholder <img> tags that specify the correct height and width. 5. Ensure That Feature Images Are Optimized to Load Early and Quickly. As the filmstrip view below shows, the feature image on the CVS.com home page doesn t render until the 17-second mark. This carousel a JavaScript feature that generates personalized content doesn t begin to load until the 2-second mark, and then demands more than 3 seconds to actually appear in the browser. Smart Network. Smart Business.

12 6. Rethink the Design and Location of Call-to-Action Links in Feature Graphics. While the accepted design convention has been to position CTA buttons at the bottom of feature banners, this convention does not always serve the best interests of users or site owners, as shoppers must wait for the image to fully render before taking their next action on the page. 7. Reformat Images. Inappropriate image formatting is an extremely common performance culprit. An image that is saved to the wrong format can be several times larger than it would be if saved to the optimal format. Images with unnecessarily high resolution waste bandwidth, processing time, and cache space. As a general rule of thumb, these are the optimal formats for common image types: Photos JPEG, PNG-24 Low complexity (few colors) GIF, PNG-8 Low complexity with transparency GIF, PNG-8 High complexity with transparency PNG-24 Line art SVG 8. Use Progressive JPEGs. Progressive JPEGs are not a new innovation. They were widely used in the 1990s, but fell out of favor due to performance issues caused by slow connection speeds and crudely rendered JPEGs; watching a progressive image load pixel by pixel was a painful experience. Now that connection speeds have improved and the way in which progressive JPEGs are created has become more sophisticated, this technique is feasible again and is returning as a newly heralded performance best practice. In one study of the top 2,000 retail sites, progressive JPEGs improved median load time by 15%. 10 (Note: While all popular browsers will render progressive images, Safari, Mobile Safari, Opera and Internet Explorer 8 render them only as baseline JPEGs, meaning there is no performance benefit.) 9. Minify Code. Minification, which is usually applied to scripts and style sheets, eliminates non-essential characters such as spaces, newline characters, and comments. A correctly minified resource is used on the client without any special processing, and file-size reductions average about 20%. Script and style blocks within HTML pages can also be minified. There are many good libraries available to perform minification, often along with services to combine multiple files into one, which additionally reduces requests. Smart Network. Smart Business. 12

13 10. Defer Loading and Executing Non-Essential Scripts. Many script libraries aren t needed until after a page has finished rendering. Downloading and parsing these scripts can safely be deferred until after the onload event. For example, scripts that support interactive user behavior, such as drag and drop, can t possibly be called before the user has even seen the page. The same logic applies to script execution. Defer as much as possible until after onload instead of needlessly holding up the initial rendering of the important visible content on the page. The script to defer could be your own or, often more importantly, scripts from third parties. Poorly optimized scripts for advertisements, social media widgets, or analytics support can block a page from rendering, sometimes adding precious seconds to load times. 11. Use AJAX for Progressive Enhancement. AJAX (Asynchronous JavaScript and XML) is a technique for using the XHR (XMLHttpRequest) object to fetch data from a Web server without refreshing the page where the code is running. AJAX enables a page to display updated data in a section of a page without reconstructing the entire page. This is often used to respond to user interaction, but it can also enable your application to load a bare-bones version of a page quickly, and then to fill in more detailed content while the user is already viewing the page. 12. Use a Content Delivery Network. Content delivery networks (CDNs) can help performance by bringing content geographically closer to users, thereby shortening round trips between the user s browser and the host server. Takeaways 1. Performance is still a critical issue for leading ecommerce sites. The ongoing increase in both time to interact and load time indicates that site owners need to continue their efforts to improve real and perceived load time for their visitors. 2. Site owners are relying on CDNs and ADCs to manage performance optimization. Content delivery networks and application delivery controllers are powerful solutions that offer many optimization benefits; however, in relying on these solutions, site owners are missing out on opportunities to make dramatic acceleration improvements elsewhere. 3. There are significant untapped opportunities to make performance gains. Site owners who want to make further acceleration gains must dig deeper for solutions. There are numerous techniques such as deferral, progressive images, and layout/design fixes that can accelerate the perception of page speed. In addition, there are dozens of advanced techniques including text/image compression, resource consolidation, and browser cache optimization which can simplify and streamline web pages in realtime, customizing them to meet the unique needs of every browser type. 4. Site owners need to study the performance of their pages in real-world scenarios. It is not enough to rely on spreadsheets and aggregate performance metrics to understand how a site performs. To truly know how visitors see a site and to identify usability issues that might otherwise be missed it is crucial to scrutinize how pages perform frame by frame, and over a real-world connection. Smart Network. Smart Business. 13

14 Methodology The tests in this study were conducted using an online tool called WebPagetest an open-source project primarily developed and supported by Google which simulates page load times from a real user s perspective using real browsers. Radware tested the home page of every site in the Alexa Retail 500 nine consecutive times. (The system clears the cache between tests.) The median test result for each home page was recorded and used in our calculations. The tests were conducted on August 29-30, 2013, via the WebPagetest.org server in Dulles, VA, using the following browsers on a DSL connection: Internet Explorer 10 Firefox 22 Chrome 29 In very few cases, WebPagetest rendered a blank page or an error in which none of the page rendered. These instances were represented as null in the test appendix. Also, in very few cases, WebPagetest.org rendered a page in more then 60 seconds (the default timeout for webpagetest.org). In these cases, 60 seconds was used for the result instead of null. To identify the time to interact (TTI) for each page, we generated a timed filmstrip view of the median page load for each site in the Alexa Retail 100. TTI is defined as the moment that the featured page content and primary call-to-action button or menu was rendered in the frame. About Radware Radware (NASDAQ: RDWR), is a global leader of application delivery and application security solutions for virtual and cloud data centers. Its award-winning solutions portfolio delivers full resilience for business-critical applications, maximum IT efficiency, and complete business agility. Radware s solutions empower more than 10,000 enterprise and carrier customers worldwide to adapt to market challenges quickly, maintain business continuity, and achieve maximum productivity while keeping costs down. For more information, please visit Sources 1 Steve Lohr, The New York Times, For Impatient Web Users, an Eye Blink Is Just Too Long to Wait, February 29, CNBC, Retailers Need for Tech Speed, November 21, Strangeloop Networks, Case Study: The impact of HTML delay on mobile business metrics, November Real User Monitoring at Walmart.com, February StatCounter Global Browser Stats, August PhoCusWright, Consumer Response to Travel Site Performance, June Strangeloop Networks, The 90-Minute Optimization Life Cycle, June Jakob Nielsen, Website Response Times, June W3C, Optimizing Content for Different Browsers: The Right Way, May Progressive JPEGs FTW! 2013 Radware, Ltd. All Rights Reserved. Radware and all other Radware product and service names are registered trademarks of Radware in the U.S. and other countries. All other trademarks and names are the property of their respective owners. Smart Network. Smart Business. 14