Have you ever heard a term but did not know what it meant? Here's a single source of truth for all site speed terminology. You’ll never be stumped again.
The ability to detect a sustained spike in website performance that’s outside normal expected variation for that page. In other words, it is an unusual delay in page performance.
A method of re-prioritizing and controlling the loading of content, especially 3rd party technologies, on a web page.
The percentage of all visitors to a website that leave after viewing just one page. High bounce rates are a sign that site performance is slow, or content does not match user expectations.
The process of storing website digital assets so that a user can access them quickly. Caching can apply to content that is proactively stored on a CDN or is stored locally on a user’s device after it has been downloaded once.
Website pages used by brands to organize products into logical groupings that make the online shopping experience easier. and more profitable. pages feature of individual products that link to their corresponding product pages organized in grids
The amount of time a user is connected to a website or a computer system.
A network of servers at various points of presence (POPs) around the world. It works by creating and storing cached copies of web content at these POPs, and serving them locally to users upon command. CDNs offer companies greater consistency and uptime by reducing strain on origin servers at times of heavy traffic, and also dramatically reduced geographic latency.
An approach to designing and optimizing web pages to induce certain user behaviors, most notably converting on a task such as making a purchase. Tactics that are commonly part of CRO include fast site performance, A/B testing, the design and placement of buttons, forms and other web elements, and the use of compelling imagery, copy, and calls-to-action.
A group of metrics from Google which aim to “reflect the real-world experience of a critical user-centric outcome.” These metrics include: First Input Delay (FID), Cumulative Layout Shift (CLS), and Largest Contentful Paint (LCP). Core Web Vitals are important as Google will begin using them as search ranking signals in addition to existing elements.
A site performance metric from Google that measures the amount of reflow on a site, with the aim to reduce any unintended clicks of a user. A reflow is a quick shift of the content displayed or layout of a page. For example, when a user is about to click a link and then the header image loads and pushes all the other content down. If a user clicked the link during this reflow, chances are they ended up clicking something else.
The five day period between Thanksgiving Day and Cyber Monday when brands experience high volumes of online holiday shopping traffic and revenue.
The length of time it takes for a DNS record to be returned from a DNS server. Interconnected computers, servers, and mobile devices need to be able to translate email addresses and domain names into meaningful numerical addresses. A DNS look up performs this function.
When the onload event fires in a browser. This typically occurs when all of the static content has loaded on the page and historically has been a good measurement for site performance.
Represents the time from page initialization to the Dom Content Loaded event or for older browsers, such as Internet Explorer, to the time the DOM is interactive.
Any element on a web page that is either personalized to a user, or updated in real time. Dynamic content impacts site performance because it must always be fetched from its origin, rather than cached, making it difficult to optimize.
A site performance metric from Google that measures how much background tasks are causing a user’s first action (clicking a button or typing a character) to be delayed. So, FID is not actually measuring the delay of a user’s first action, but the delay caused before that event. An example is when a browser is very busy Dom building or trying to accomplish a bunch of background tasks. Because if the browser is busy, then a user’s interactivity will be delayed.
Front-end performance refers to how quickly a visitor’s browser can execute and render the application content once it has been downloaded. FEO, then, is a sub-category of the broader web performance optimization field, focusing specifically on techniques related to the content itself, rather than how the content is stored or how it gets from point A to point B. It includes techniques like image compression, script concatenation, minification, image spriting, and more.
The process of reducing the file size of website images without sacrificing quality so that page load times remain low.
A site performance metric from Google that measures when a good portion of the screen is visible to a user. Typically, for eCommerce sites this is when the hero image is displayed or when the carousel image appears.
A technique for loading web content when it is needed rather than all at once.
A coordinated approach employed by retailers to interact with and serve customers across multiple touchpoints, including online, mobile, in-store, and more.
An onload event occurs when a website object has been loaded. It is most often used within the <body> element to execute a script once a web page has completely loaded all content (including images, script files, CSS files, etc.).
In terms of eCommerce, an order is an online request from a consumer to purchase goods or services from a brand's website.
An instance of a page being loaded (or reloaded) in a browser. Page views is a metric defined as the total number of pages viewed on a website, usually measured over the course of a month.
A rating that indicates how an individual 3rd party technology affects page load times. The PIR is calculated by adding the 3rd party's performance violations and the delay page load violations together and then dividing by the number of page views of the site.
A type of web design that seeks to achieve a quality user experience on a screen of any size, with the same URL. This is opposed to the method of identifying a user’s device and redirecting a user to a separate version of the website (and “m.dot” site).
The ability of a website to handle growth and the demands that may accompany it. Scalable systems can quickly be adjusted to meet the needs of a website that experiences a heavy surge in traffic.
A metric that represents the number of single visits to a website. Whether a user lands on a web page and leaves a few seconds later, or spends an hour reading every blog post on the site, it still counts as a single session. A session can include many page views, if a user navigates to other web pages on a website without leaving.
A graphical representation of a page’s load process. It visually displays each asset that composes a web or mobile application, and uses horizontal bars to show how long each asset took to download. At the most basic level, a longer bar is a longer download time, and color codes mark various stages in an individual element’s journey to a end user’s screen.Columns in the chart provide information on WHAT the asset is, WHERE the asset comes from (be it your origin server, or a third party), how HEAVY the asset is (in B, KB, MB), and the STATUS of the asset (if there was an error involved in its delivery or not).
All content that doesn’t update on an automated basis is called static content. On most websites, the basic structure, navigation elements, images, and text are all static, and can thus be stored in a cache, either on a CDN or locally in a user’s browser.
The elapsed time from the moment a user requests a page to the moment all visual elements of the page have been rendered. If sequencing or lazyloading is in place, this will only apply to the elements that are visible “above the fold” in a user’s viewport.
Refers to the time between the browser requesting a page and when it receives the first byte of information from the server. This time includes DNS lookup and establishing the connection using a TCP handshake and SSL handshake if the request is made over https.
A performance metric that measures when a web page’s sub-resources have all been downloaded and the user can interact with the web page.
Measures the delay between the request sent by the browser and the receiving of the last byte of the related response (the last piece of the HTML document).
The elapsed time from the moment a user requests a page to the moment the visual elements of the page start to appear in the browser.
The elapsed time from the moment a user requests a page to the moment the page title appears in the browser tab.
TTL is the length of time before a cache is automatically refreshed, so that it serves content that reflects changes that may have been made since the last time the cache captured data. Pages that have content that almost never changes can be set with a very long “far-future” TTL, so that effectively it will stay cached forever unless it is manually changed. Other app content changes daily or weekly, and can be set with a TTL that reflects its scheduled changes. Other content is subject to change so frequently that it should not be cached at all.
The encompassing term for how a user interacts with a web application. It includes considering everything from the performance of the initial page load, to the design and functionality of the pages, to the processing of transactions. Basically, every aspect of a web app that a user can percieve can be counted as part of a user experience.
In the broadest sense, WPO is the process, methodology, and various techniques to measure, benchmark and improve site performance, where performance refers to the speed at which pages are rendered on the end-user’s browser. More simply put, WPO is the art of tuning a web application for faster and smoother page loads, and an overall improved user experience.
An evaluation from a Site Performance Engineer to gain insight into how an eCommerce site is currently performing and determine the impact of all 3rd party eCommerce technologies on site performance.