Detect if user is using webview for android/iOS or a regular browser

Detecting browser for iOS devices is different from the Android one. For iOS devices you can do it by checking user agent using JavaScript:

var userAgent = window.navigator.userAgent.toLowerCase(),
    safari = /safari/.test( userAgent ),
    ios = /iphone|ipod|ipad/.test( userAgent );

if( ios ) {
    if ( safari ) {
        //browser
    } else if ( !safari ) {
        //webview
    };
} else {
    //not iOS
};

For Android devices, you need to do it through server side coding to check for a request header.

PHP:

if ($_SERVER['HTTP_X_REQUESTED_WITH'] == "your.app.id") {
    //webview
} else {
    //browser
}

JSP:

if ("your.app.id".equals(req.getHeader("X-Requested-With")) ){
    //webview
} else {
    //browser
}

Ref:detect ipad/iphone webview via javascript

Note: This solution is PHP-based. HTTP headers can be faked so this is not the nicest solution but you can have a start with this.

//For iOS

if ((strpos($_SERVER['HTTP_USER_AGENT'], 'Mobile/') !== false) && (strpos($_SERVER['HTTP_USER_AGENT'], 'Safari/') == false) {
    echo 'WebView';
} else{
    echo 'Not WebView';
}

//For Android

if ($_SERVER['HTTP_X_REQUESTED_WITH'] == "com.company.app") {
    echo 'WebView';
} else{
    echo 'Not WebView';
}

This is the extended version of rhavendc's answer. It can be used for showing app install banner when a website is visited from browser, and hiding the banner when a website is opened in a webview.

$iPhoneBrowser  = stripos($_SERVER['HTTP_USER_AGENT'], "iPhone");
$iPadBrowser    = stripos($_SERVER['HTTP_USER_AGENT'], "iPad");
$AndroidBrowser = stripos($_SERVER['HTTP_USER_AGENT'], "Android");
$AndroidApp = $_SERVER['HTTP_X_REQUESTED_WITH'] == "com.company.app";
$iOSApp = (strpos($_SERVER['HTTP_USER_AGENT'], 'Mobile/') !== false) && (strpos($_SERVER['HTTP_USER_AGENT'], 'Safari/') == false);

if ($AndroidApp) {
    echo "This is Android application, DONT SHOW BANNER";
}
else if ($AndroidBrowser) {
    echo "This is Android browser, show Android app banner";
}
else if ($iOSApp) {
    echo "This is iOS application, DONT SHOW BANNER";
}
else if($iPhoneBrowser || $iPadBrowser) {
    echo "This is iOS browser, show iOS app banner";
}

For me this code worked:

var standalone = window.navigator.standalone,
  userAgent = window.navigator.userAgent.toLowerCase(),
  safari = /safari/.test(userAgent),
  ios = /iphone|ipod|ipad/.test(userAgent);

if (ios) {
  if (!standalone && safari) {
    // Safari
  } else if (!standalone && !safari) {
    // iOS webview
  };
} else {
  if (userAgent.includes('wv')) {
    // Android webview
  } else {
    // Chrome
  }
};