The majority of end user response time occurs on the front end, so website performance monitoring is accordingly focused there. This stands in contrast to Application Performance Monitoring (APM), which traces a transaction’s performance through its back end services.
Let’s take a deeper look at web performance metrics and web performance analytics.
- Metrics: Identify the web performance metric data to be measured
- Analysis: Apply data analysis to transform the metric data into information
Web Performance Metrics
Web performance metrics are generally discussed as web/IT metrics. The technology stack and architecture used to present a site or application to an end user will provide efficacy support for determining which metrics are most important for that specific use case. Web performance metrics typically include page load times, DNS times, server times, response times, file size, and others. When discussed as part of a business use case, such as web performance optimization, the most relevant metrics may include shopping cart size, conversion rates, time on page, and number of page views. Here are the top ten web performance metrics to measure when focusing your overall web optimization efforts.
Top Web Performance Metrics
- DNS Time (or DNS Lookup Time): The amount of time required to resolve the domain name to an IP address. Every request starts in this way.
- Connection Time: The time required to establish the TCP connection with the IP address of the resolved domain name (the connection process is also known as the TCP handshake).
- SSL Handshake Time: The amount of time taken to establish the SSL handshake with the primary URL.
- Wait Time to First Byte (TTFB): The length of time between a client making an HTTP request to when the client receives the first byte of the request’s response.
- Response Time: The duration load time from when a client receives the first byte of the response to when the client receives the last byte of the response.
- First Contentful Paint (FCP): FCP measures the length of time it takes for the browser to render the first bit of content from the document object model (DOM). This is an important metric because it provides the first piece of feedback to the user on how the page is loading.
- Largest Contentful Paint (LCP): LCP is a Google Web Vitals metric, which measures when the largest content element on a page becomes visible.
- First Input Delay (FID): FID measures load responsiveness by assessing the time it takes from when a user first interacts with a page to the time when the browser can begin to process responses for that interaction.
- Total Downloaded Bytes (or Page Size): The total sum of downloaded bytes for all files included on the webpage. This can also be thought of as the total size of the data transferred between the server(s) and the client.
- Document Complete Time: The point in time when the browser onload event fires. This is generally when all static page content has fully loaded.
- Fully Loaded Time: The time it takes for the client to fully render any and all requests; it measures from the start of navigation to the last byte of the last received request, including any lazy-loaded, post-document complete requests.
"Web performance metrics typically include page load times, DNS times, server times, response times, file size, and others. When discussed as part of a business use case, such as web performance optimization, the most relevant metrics may include shopping cart size, conversion rates, time on page, and number of page views."