navigator Object

`navigator` Object Properties

The navigator object, part of the Browser Object Model, contains a variety of information about the browser / device / user agent.
Not all browsers will recognize or properly support all of the properties of the navigator object, in part because the object was not part of a standard for a long time and each browser has tended to have some properties that are unique to it.
The table of navigator properties references the most commonly used ones; there are additional properties that are browser-specific which are omitted.
View a list of all your browser's navigator properties / values; a for-in loop is used to extract and display this information.
Historically, the primary use of these properties was to detect the browser being used, although it can also help answer other questions (such as whether cookies are enabled) and more recently it is used as part of the Geolocation API.

Property	Description	Your Value
cookieEnabled	Returns `true` if cookie support is enabled. Returns `false` if cookie support is disabled. If your browser lacks support this will be `null` or `undefined`.
geolocation	Ties into a Geolocation API, which has various methods called: `navigator.geolocation.getCurrentPosition()` `navigator.geolocation.watchPosition()` `navigator.geolocation.clearWatch()`	N/A
language	The language setting for your browser, if supported. 'en' is English.
onLine	Returns `true` if the browser/device is online. Returns `false` if the browser/device is offline. If your browser lacks support this will be `null` or `undefined`.
serviceWorker	This allows you to access service workers, which are web workers that operate outside of the main JavaScript thread and can process tasks in parallel with other operations happening in the main thread.	N/A
userAgent	The user agent string for your browser; this is also sent to the web server with each file request as part of the headers. This property offers unique data for identifying different browsers. The primary drawback is that its value can be changed, so you should not rely on it for critical tasks.

Considerations in Browser Detection

Browser detects should only be used as a last resort.
- Object detection is preferable, but sometimes browsers "support" the same object but handle it differently so simply detecting the object is insufficient.
- Sample object detection:
```
if (document.querySelector) {
  // code involving document.querySelector
}
```
- Or the issue requiring browser-specific changes has nothing to do with object detection (such as navigation menus being off by a few pixels on Mac browsers, compared to Windows browsers).
- If there is some other way to isolate a browser that is also preferable to browser detection. Some options:
  - CSS media query parameters particular to a given browser/device
  - @supports CSS at-rule
- These are better than browser detection because the user cannot turn them off or change them; the browser either matches the criteria or it does not.
No browser detection script will cover every user agent.
- New browsers are introduced.
- Existing browsers get updated and change their navigator details.
- There are always obscure browsers being used.
- As a result, you are continually updating your browser detection script and it is not always easy to go back and fix existing websites (you may not even realize they are "broken" for quite a while, unless a user reaches out to tell you).
There is always the risk of improperly detecting a browser.
- This is termed a false positive.
- The practice of websites using browser detection has made this problem more common, as it creates a need to change the user agent (and this can be changed via a browser plugin or in browser settings).
Server-side detection is more reliable than client-side detection, but is still far from perfect or reliable.
- The client-side language (JavaScript) can be disabled, thus wiping out the detection.
- Server-side detection occurs regardless (it cannot be disabled by the user). However, changes to the user agent string can still defeat this detection.
Browser detection can be impacted by third parties or have unanticipated effects on other parties.
- Proxy servers sometimes scramble the user agent string, rendering the detection code useless.
- Poorly written server-side browser detection could read a search engine spider's user agent string, not recognize it, and redirect the spider to an alternate version of the website or give them an error message. This behavior would potentially deal a serious blow to search engine ranking, because the indexing is derailed.

navigator Object

navigator Object Properties

Considerations in Browser Detection

`navigator` Object Properties