Getting started with Web Performance Assessment

Yottaa's Web Performance Assessment provides people that are interested in their website's performance a complete picture, based on:
1) Yottaa Score
2) Four different factors that make up a website's performance

Yottaa Score is the numeric score we assign a web page in assessing its user experience. The score ranges from 0 to 100, with a higher score meaning a better (faster) page loading experience.

Yottaa Score takes into consideration each of the key timing metrics of page loading, as well as the "speed" with which the page loading process progresses from one key milestone to the next. It's all about the end user's perspective. The key timing metrics are:

• Time to Title
• Time to First Paint (also referred to as "Time to Start Render")
• Time to Display
• Time to Interact

Traditionally, most people have used "Time to Interact" as the primary metric for judging how fast a web page loads. In fact, a lot of web performance monitoring tools still rely on it. However, the web has evolved and no single timing metric alone is sufficient for judging whether a web page loads fast or not. For example:

                           Time to First Paint       Time to Interact
 Web page A:                    8 second                   10 second
 Web page B:                    2 second                   12 second

Web page A has a shorter Time to Interact than web page B. But visitors to web page A are staring at a blank screen for 8 seconds. That is eternity in today's web environment. Obviously web page B in the above example has a much better user experience.

What is a good Yottaa Score? If your site gets a score of 70 or above, it is good.

Four Factors for Website Speed

1.) Global Reachability - This tells you how quickly a vistor to your website can resolve your hostname using DNS and download the initial HTML file from your servers. We currently measure Global Reachability from 5 data centers around the world. At each data center, our monitoring agents will initiate recursive DNS lookups and HTTP requests, then collect and store all the timing information for the requests and responses.

2.) User Experience - Using a real web browser, a monitoring agent in each data center will load the URL that was entered into Yottaa and collect the timing information for all the assets that the web browser loads to display your webpage. Yottaa turns all the timing information into four high-level metrics you can use to assess the User Experience of your webpage.

• Time to Title - Timing information on how quickly the title to the web browser changes. For a web visitor, it is the second indication that your website is working. (The "connecting" status indicator in the status bar area of most browsers is the first, but the title is the first concrete and reassuring sign that a page will be loaded.)
• Time to First Paint - The time at which the browser paints your webpage for the first time. The quicker the browser paints the first pixel, the better. Users expect to see your webpage appear quickly, so the longer you delay the webpage from rendering to the screen the more likely they will be to leave.
• Time to Display - This is the time at which the DOMDocumentComplete event is fired by the web browser. It provides a good proxy for when the page is visibly rendered so the user can begin viewing or reading it, though it's not really finished yet.
• Time to Interact - This is the time at which the onload event is fired by the web browser. Developers use this event to inject user behavior into the webpage to provide advanced user experience capabilities to the page. A webpage that uses a lot of JavaScript to enhance the page after it loads will typically leverage asynchronous techniques to avoid delaying this key metric more than necessary.

3.) Complextity - Using the information captured from the web browser, Yottaa breaks down the assets within your webpage by their type (e.g. JavaScript, CSS, and images). This provides you additional insight into your web page: 1.) Number of requests per asset type and 2.) the combined size of each type of asset.

4.) YSlow -Yottaa provides you a list of YSlow recommendations, which are specific performance optimization techniques for you to apply to your page in order to improve the user experience.