Authors:Peter Higgins, Ben Lowery

You should always try to use feature detection (See general overview Using Capability Detection) whenever possible to write forward-compatible code branches. The dojo/has API is designed to help in this endeavor.

For when feature detection is not an option, Dojo provides user agent sniffing code in the module, dojo/sniff. The sniff module augments the basic set of has() tests (see dojo/has) with additional user agent based tests, so you can use the base has() api to test for browser environment and versions, just like you do for other features. Using this approach in conjunction with an optimizing compiler at build time, it is possible to optimize out unwanted code paths for specific browsers. This reduces the size and increases the performance of your code.


The module can be used in two ways, because the module adds features to dojo/has and returns dojo/has as its return value. Both examples below are functionally equivalent:

require(["dojo/sniff"], function(has){
    // Do something specific for IE.
require(["dojo/has", "dojo/sniff"], function(has){
    // Do something specific for IE.

The module defines the following has-features:

Feature Notes
air Detects Adobe AIR Environments
webkit Detects Webkit based environments 1.3+
mac Detects if the platform is Mac OSX
quirks If the browser is running in “quirks” mode
ios Detects iOS devices
android Detects Android devices
bb Detects BlackBerry devices
chrome Detects Google Chrome 1.3+ browser
safari Detects Safari browser
opera Detects Opera browser
mozilla Detects Mozilla browser
ff Detects Firefox browser.
ie Detects Internet Explorer browser.
wii Detects if running on a Nintendo Wii
svg Detects SVG support

Each feature will only return a truthy value if the specified browser is being used. For example if you are using Internet Explorer has("ie") will only return a truthy value, where as has("chrome") will return false.

The value returned, where appropriate, will provide the version number of the browser, so specific code checks can be done for versions. For example:

require(["dojo/has", "dojo/sniff"], function(has){
  if(has("ie") <= 6){ // only IE6 and below
    // ...

  if(has("ff") < 3){ // only Firefox 2.x and lower
    // ...

  if(has("ie") == 7){ // only IE7
    // ...


Basic browser detection example.

require(["dojo/has", // alias has API to "has"
    "dojo/_base/array", // alias array API to "arrayUtil"
    "dojo/dom", // alias DOM API to "dom"
    "dojo/sniff", // load browser-related has features
    "dojo/domReady!" // wait until DOM is loaded
], function(has, array, dom){

  function makeFancyAnswer(who){
      return "Yes, it's version " + has(who);
      return "No";

  function makeAtLeastAnswer(who, version){
    var answer = (has(who) >= version) ? "Yes" : "No";
    dom.byId("isAtLeast" + who + version).innerHTML = answer;

  array.forEach(["ie", "mozilla", "ff", "opera", "webkit", "chrome"], function(n){
    dom.byId("answerIs" + n).innerHTML = makeFancyAnswer(n);

  makeAtLeastAnswer("ie", 7);
  makeAtLeastAnswer("ff", 3);
  makeAtLeastAnswer("opera", 9);

  <dt>Is this Internet Explorer?</dt>
  <dd id="answerIsie"></dd>
  <dt>Is this Firefox?</dt>
  <dd id="answerIsff"></dd>
  <dt>Is this Mozilla?</dt>
  <dd id="answerIsmozilla"></dd>
  <dt>Is this Opera?</dt>
  <dd id="answerIsopera"></dd>
  <dt>Is this WebKit? (Dojo 1.3)</dt>
  <dd id="answerIswebkit"></dd>
  <dt>Is this Chrome? (Dojo 1.3)</dt>
  <dd id="answerIschrome"></dd>
  <dt>Is this at least IE 7?</dt>
  <dd id="isAtLeastie7"></dd>
  <dt>Is this at least Firefox 3?</dt>
  <dd id="isAtLeastff3"></dd>
  <dt>Is this at least Opera 9?</dt>
  <dd id="isAtLeastopera9"></dd>

See Also

  • dojo/has - The main feature detection module of Dojo.

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