Calculate your Server-Timing Report (STR) score based on component timings.
STR Score: —
Understanding the STR Calculator
The STR (Server-Timing Report) Calculator is a tool designed to help developers and website administrators quantify the performance of their web server and the rendering process of a webpage. It takes various critical timing metrics, typically captured via the browser's Navigation Timing API or the Server Timing header, and combines them into a single, interpretable STR score. A lower score indicates better performance.
Why Measure Server and Page Load Times?
Website performance is crucial for user experience, search engine optimization (SEO), and conversion rates. Slow-loading pages lead to user frustration, higher bounce rates, and can negatively impact search engine rankings. By breaking down the load time into its constituent parts, the STR calculator helps pinpoint bottlenecks.
The Components of the STR Calculator
DNS Lookup Time: The time it takes for the browser to resolve the website's domain name into an IP address.
Connection Time: The time required to establish a TCP connection to the server.
SSL Handshake Time: For HTTPS sites, this is the time taken for the SSL/TLS handshake to complete, securing the connection.
Server Processing Time: The time the server itself takes to generate the requested content before sending the first byte.
Time to First Byte (TTFB): The duration from the start of the request to the moment the first byte of the response is received. This includes DNS, connection, SSL, and server processing.
DOM Interactive Time: The time when the HTML document has been completely loaded and parsed, and the browser can start interacting with the DOM (Document Object Model).
DOM Complete Time: The time when the entire page, including all its resources (images, scripts, CSS), has finished loading and parsing. This is often considered the "fully loaded" time.
How the STR Score is Calculated
The STR score is a weighted sum of the individual timing components. The exact weighting can vary, but a common approach prioritizes the end-user perceived performance. In this calculator, we use a simplified, yet effective, formula that emphasizes the total time to perceived interactivity and completion, while also factoring in initial connection overheads.
The formula implemented is:
STR Score = (DNS Lookup + Connection Time + SSL Handshake Time) * 2 + Server Processing Time + DOM Interactive Time + DOM Complete Time
The multiplication of the initial connection phases by 2 emphasizes that any delay in these early stages can have a disproportionately negative impact on the overall user experience, as they are foundational to everything that follows. Server processing and DOM times are added directly, as they represent the core work done to deliver content and make it usable.
Interpreting Your STR Score
0-800 ms: Excellent performance. Your server and page load are highly optimized.
801-2000 ms: Good performance. Room for minor improvements.
2001-4000 ms: Average performance. Significant optimization opportunities exist.
4000+ ms: Poor performance. Urgent attention is needed to address bottlenecks.
Remember that these are general guidelines. The acceptable STR score can vary depending on your target audience, industry, and the complexity of your website.
Use Cases for the STR Calculator
Diagnosing slow website load times.
Comparing performance before and after optimization efforts.
Monitoring server health and response times.
Identifying which part of the request lifecycle is most time-consuming.
Setting performance benchmarks for development teams.
function calculateSTR() {
var dnsLookup = parseFloat(document.getElementById("dnsLookup").value);
var connectionTime = parseFloat(document.getElementById("connectionTime").value);
var sslTime = parseFloat(document.getElementById("sslTime").value);
var serverProcessingTime = parseFloat(document.getElementById("serverProcessingTime").value);
var firstByteTime = parseFloat(document.getElementById("firstByteTime").value); // Note: TTFB is often calculated as connection + SSL + server processing
var domInteractiveTime = parseFloat(document.getElementById("domInteractiveTime").value);
var domCompleteTime = parseFloat(document.getElementById("domCompleteTime").value);
var scoreValue = document.getElementById("scoreValue");
// Validate inputs: Ensure they are numbers and not negative
if (isNaN(dnsLookup) || dnsLookup < 0 ||
isNaN(connectionTime) || connectionTime < 0 ||
isNaN(sslTime) || sslTime < 0 ||
isNaN(serverProcessingTime) || serverProcessingTime < 0 ||
isNaN(domInteractiveTime) || domInteractiveTime < 0 ||
isNaN(domCompleteTime) || domCompleteTime < 0) {
scoreValue.innerText = "Invalid Input";
scoreValue.parentNode.style.backgroundColor = "#dc3545"; // Red for error
return;
}
// Calculate STR Score using the defined formula
// STR Score = (DNS Lookup + Connection Time + SSL Handshake Time) * 2 + Server Processing Time + DOM Interactive Time + DOM Complete Time
var strScore = (dnsLookup + connectionTime + sslTime) * 2 + serverProcessingTime + domInteractiveTime + domCompleteTime;
// Handle cases where the calculated score might be very low due to zero inputs
if (strScore < 0) {
strScore = 0;
}
scoreValue.innerText = strScore.toFixed(0) + " ms";
scoreValue.parentNode.style.backgroundColor = "var(–success-green)"; // Reset to green on success
}