This table is a cheat sheet for determining which browser engine a visitor is using, although this can be alterered by the visitor or by antivirus software, etc., so is not going to always be reliable or fool-proof.
Some browsers will report multiple user agents or other browser’s user agents, and so for Firefox, Chrome and Safari we must check that another user agent string is not present, to avoid a false positive.
| BROWSER Engine | Must contain | Must not contain |
|---|---|---|
| Firefox | Firefox | Seamonkey |
| Seamonkey | Seamonkey | |
| Chrome | Chrome | Chromium |
| Chromium | Chromium | |
| Safari | Safari | Chrome or Chromium |
| Opera 15+ (Blink-based engine) | OPR | |
| Opera 12- (Presto-based engine) | Opera | |
| Internet Explorer 10- | MSIE | |
| Internet Explorer 11 | Trident |
Example use in JavaScript:
if ( navigator.userAgent.indexOf("Firefox") !== -1 &&
navigator.userAgent.indexOf("Seamonkey") === -1 )
{
  // We can assume this visitor is using Firefox,
// as it contains the word Firefox but not the word Seamonkey.
}
Example use in PHP:
if( stripos($GLOBALS["useragent"], "Chrome") !== FALSE &&
stripos($GLOBALS["useragent"], "Chromium") === FALSE )
{
  // Here we can assume the browser engine is Chrome, as it
// contains the word Chrome but not the word Chromium.
}