Timings for HTTP requests

Usage no npm install needed!

<script type="module">
  import abellsmytheRequestTime from 'https://cdn.skypack.dev/@abellsmythe/request-time';



Timings for HTTP requests

Understanding and measuring HTTP timings helps us to discover performance. bottlenecks in client to server or server to server communication.

Request Timing

Timings explained

  • DNS Lookup: Time spent performing the DNS lookup. DNS lookup resolves domain names to IP addresses. Every new domain requires a full round trip to do the DNS lookup.

    • There is no DNS lookup when the destination is already an IP address.

  • TCP Connection: Time it took to establish TCP connection between a source host and destination host. Connections must be properly established in a multi-step handshake process. TCP connection is managed by an operating system, if the underlying TCP connection cannot be established, the OS-wide TCP connection timeout will overrule the timeout config of our application.

  • TLS handshake: Time spent completing a TLS handshake. During the handshake process endpoints exchange authentication and keys to establish or resume secure sessions.

    • There is no TLS handshake with a not HTTPS request.

  • Time to First Byte (TTFB): Time spent waiting for the initial response. This time captures the latency of a round trip to the server in addition to the time spent waiting for the server to process the request and deliver the response.

  • Content Transfer: Time spent receiving the response data. The size of the response data and the available network bandwidth determinates its duration.



npm install @abellsmythe/request-time


'use strict';

const https = require('https');
const timer = require('@abellsmythe/request-time').default;

const request = https.get('https://google.com');
const timings = timer(request);

request.on('response', response => {
    response.on('data', () => {
        // Do something
    response.on('end', () => {
    start: 20019170.414002,
    socket: 20019171.943738,
    dnsLookup: 20019182.811348,
    connect: 20019194.637675,
    tlsHandshake: 20019245.32874,
    upload: 20019246.615841,
    response: 20019284.613933,
    end: 20019288.80115,
    error: undefined,
        wait: 1.5297359973192215,
        dns: 10.86761000007391,
        tcp: 11.826326999813318,
        request: 51.9781660027802,
        firstByte: 37.998091999441385,
        download: 4.187217000871897,
        total: 118.38714800029993



Returns: Object

  • start - Time when the request started.
  • socket - Time when a socket was assigned to the request.
  • dnsLookup - Time when the DNS lookup finished.
  • tlsHandshake - Time when the secure connection is done.
  • connect - Time when the socket successfully connected.
  • upload - Time when the request finished uploading.
  • response - Time when the request fired the response event.
  • end - Time when the response fired the end event.
  • error - Time when the request fired the error event.
  • phases
    • wait - timings.socket - timings.start
    • dns - timings.dnsLookup - timings.socket
    • tcp - timings.connect - timings.dnsLookup
    • request - timings.upload - timings.connect
    • firstByte - timings.response - timings.upload
    • download - timings.end - timings.response
    • total - timings.end - timings.start or timings.error - timings.start

If something is not measured yet, it will be undefined.

Note: The time is a number representing the milliseconds without elapsing since the UNIX epoch.

Note: request-time uses process.hrtime() from node as it's not a subject of clock drift