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Detecting robots and webcrawlers by User-Agent string

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The web is full of robots. If you manually collect pageview statistics, they'll definitely be full of requests made by webcrawlers. This post explains a simple but effective approach for detecting webcrawlers by User-Agent string.

The function below will detect many types of robots:

function is_robot(string $userAgent)
    if (! $userAgent) {
        return true;
    $userAgent = mb_strtolower($userAgent);
    foreach ([
        'bot', 'crawl', 'slurp', 'spider', 'facebook', 'mediapartners', 'ohdear', 'guzzlehttp',
        'anthill', 'apis-google', 'iframely', 'node-fetch', 'turnitin', 'pocketparser', 'java/1',
        'go-http-client', 'curl/',    
    ] as $word) {
        if (str_contains($userAgent, $word)) {
            return true;
    return false;

The code above won't detect all robots, but it will detect most of them.

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