User Agent Strings and Detection

In the user agent request header field, Amazon Silk sends one of three user agent strings, depending on the view requested on the device by the customer. If a specific view is not requested, the view defaults to Tablet for Fire tablets, and Mobile for Fire phones. If a site has compatibility issues when rendered in the default view, a different view may be selected by the device. The templates for the Amazon Silk user agents are shown below.

Tablet

Mozilla/5.0 (Linux; Android android-version; product-model Build/product-build) AppleWebKit/webkit-version (KHTML, like Gecko) 
    Silk/browser-version like Chrome/chrome-version Safari/webkit-version

Desktop

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/webkit-version (KHTML, like Gecko) 
    Silk/browser-version like Chrome/chrome-version Safari/webkit-version

Mobile

Mozilla/5.0 (Linux; Android android-version; product-model Build/product-build) AppleWebKit/webkit-version (KHTML, like Gecko) 
    Silk/browser-version like Chrome/chrome-version Mobile Safari/webkit-version

Note

Red and italics indicates variable fields, which are described below.

Template fields

• android-version – The Android platform version (for example, 4.4.3).

• product-model – The value of Build.MODEL (for example, KFTT).

  For a complete list of the product models, see Screen Resolution.

• product-build – The value of Build.ID (for example, IML74K).

• webkit-version – Indicates the version of WebKit used (for example, 535.19). The version can change whenever the Fire device receives a software update.

• browser-version – Indicates the version of the Amazon Silk browser (for example, 44.1.54). The version can change whenever the Fire device receives a software update.

• chrome-version – The version of Google Chrome with which the Amazon Silk browser is compatible.

User Agent String Examples

Examples of the Amazon Silk User Agent String

Tablet

Mozilla/5.0 (Linux; Android 4.4.3; KFTHWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) 
    Silk/44.1.54 like Chrome/44.0.2403.63 Safari/537.36

Desktop

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) 
    Silk/44.1.54 like Chrome/44.0.2403.63 Safari/537.36

Mobile

Mozilla/5.0 (Linux; U; Android 4.4.3; KFTHWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) 
    Silk/44.1.54 like Chrome/44.0.2403.63 Mobile Safari/537.36

UA for Kindle Fire 1st Generation

Note

The UA for the Kindle Fire 1st Generation follows a slightly different syntax.

In the examples below, red and italic text indicates variable fields. The Amazon Silk-Accelerated value can be either true or false, depending upon customer selection.

Desktop/Tablet

Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-us; Silk/1.0.13.81_10003810) AppleWebKit/533.16 (KHTML, like Gecko) Version/5.0 Safari/533.16 Silk-Accelerated=true

Mobile

Mozilla/5.0 (Linux; U; Android 2.3.4; en-us; Silk/1.0.13.81_10003810) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1 Silk-Accelerated=true

User Agent Detection

You can use JavaScript to detect the Amazon Silk user agent across various Kindle Fire device families. Unless you want to provide a unique experience for different Kindle Fire devices, we recommend a general match that will work over time as product models and version numbers change. The following examples illustrate best practices for matching the Amazon Silk user agent across Kindle Fire device types.

Note

You can use user agent detection to target content, but this approach can be problematic. User agent detection requires you to keep track of the browsers your customers use and the features that those browsers support. Those variables will change over time, so user agent detection isn't future proof. User agent detection can be useful if feature detection is expensive or if a particular feature is only partially implemented by a browser. But in most cases, feature detection is the right choice. For more information, see Feature Detection.

Note

The tests below also match the user agent string for the PlayStation Vita browser. If this is a concern, you can exclude that browser using the following condition:

!/Playstation/.test(navigator.userAgent)

To detect Amazon Silk

if (/\bSilk\b/.test(navigator.userAgent)) {
    alert("Silk detected!");
}

To detect the Amazon Silk version

var match = /\bSilk\/([0-9._-]+)\b/.exec(navigator.userAgent);
if (match) {
    alert("Detected Silk version "+match[1]);
}

To detect mobile/desktop preference

var match = /\bSilk\/(.*\bMobile Safari\b)?/.exec(navigator.userAgent);
if (match) {
    alert("Detected Silk in mode "+(match[1] ? "Mobile" : "Default (desktop)"));
}

To detect multiple variables at once

var match = /(?:; ([^;)]+) Build\/.*)?\bSilk\/([0-9._-]+)\b(.*\bMobile Safari\b)?/.exec(navigator.userAgent);
if (match) {
    alert("Detected Silk version "+match[2]+" on device "+(match[1] || "Kindle Fire")+" in mode "+(match[3] ? "Mobile" : "Default (desktop)"));
}