GET请求中的“ _”参数[重复]

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                        <a href="/questions/3687729/who-add-single-underscore-query-parameter" dir="ltr">Who Add “_” Single Underscore Query Parameter?</a>
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                                (4 answers)
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            <div class="grid--cell mb0 mt8">Closed <span title="2014-08-01 21:14:16Z" class="relativetime">5 years ago</span>.</div>
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I have noticed in several websites recently the '_' parameter which appears to be set to a random string. eg:

 stackoverflow.com/?_=12345678

What is the purpose of this parameter and how is the number generated?

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Answer 1

Adding a random numerical param to requests is a common way to defeat browser caching of AJAX result sets.