UA Freeze / User-Agent reduction: how to detect Chrome's frozen user-agent string

Code Samples
This page contains code samples illustrating how you can recognize "frozen" User-Agent strings. You can easily adapt these code samples to implement HTTP redirects to pages that explain the problem or offer alternatives to the fully-fledged service that non-frozen User Agents are getting.

You can freely use and adapt the code snippets provided below to determine whether the web browser has implemented the Chrome strategy to "freeze the UA string" (i.e. provide a generic and virtually insignificant version of the UA string).

Python 3

#!/usr/bin/env python3
# License: Public Domain

roots = [
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (X11; CrOS x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/"
]


def isFrozen(ua):
    '''Look for evidence of a frozen user-agent string'''
    
    if not ".0.0.0" in ua:
        return False

    if not any(map(ua.__contains__, roots)):
        return False

    if not "Safari/537.36" in ua:
        return False

    return True

def is_it_cold(ua):

    if isFrozen(ua):
        print("FROZEN!")
    else:
        print("NOT Frozen")


#some frozen UAs first
uas = ["Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (X11; CrOS x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Mobile Safari/537.36"
        ]

#couple of old warm UA strings
uas.append("Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2; .NET4.0C; MSOffice 12)")
uas.append("Mozilla/5.0 (Linux; U; Android 2.3.5; en-us; MB855 Build/4.5.1A-1_SUN-254_13) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1")    

for u in uas:
    print("Inspecting "+u)
    is_it_cold(u)
    print()

JavaScript


<script>
// Licence: Public domain

var roots = [
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (X11; CrOS x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/",
    "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/"
]

function isFrozen(ua) {
    // Look for evidence of a frozen user-agent string
    
    if (!ua.includes(".0.0.0")) {
        return false
    }

    // ECMAScript 5, see here for alternatives
    // https://stackoverflow.com/questions/5582574/how-to-check-if-a-string-contains-text-from-an-array-of-substrings-in-javascript
    if (!roots.some(substring=>ua.includes(substring))) {
        return false;
    }

    if (!ua.includes("Safari/537.36")) {
        return false
    }
    return true
}

function is_it_cold(ua) {

    if (isFrozen(ua)) {
        return "FROZEN!";
    } else {
        return "NOT Frozen";
    }
}

// some frozen UAs first, last two are warm (i.e. not frozen)
var uas = ["Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (X11; CrOS x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Safari/537.36",
        "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/999.0.0.0 Mobile Safari/537.36",
        "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2; .NET4.0C; MSOffice 12)",
        "Mozilla/5.0 (Linux; U; Android 2.3.5; en-us; MB855 Build/4.5.1A-1_SUN-254_13) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1"
        ];

uas.forEach((u, i) => console.log("Inspecting "+u+"\n"+is_it_cold(u)));
</script>