Who Add "_" Single Underscore Query Parameter?

php javascript ajax apache http

30,264

Solution 1

jQuery adds a parameter like that to get around IE's caching.

edit: it only adds it for get requests, and only if the option cache is false:

cache: false

Solution 2

It could be the JQuery CacheBuster parameter.

Resources :

Solution 3

Probably it's a dummy parameter added by the reverse proxy to force non-cached content to be served.

Solution 4

1283458471913 is a unix timestamp in ms, probably a bot/proxy making sure that they get a fresh page and not a cached version.

Could also be jQuery which would cause this for AJAX request of you have the nocache attribute set to true.

if ( s.cache === false && type == "GET" ) {
    var ts = now();
    // try replacing _= if it is there

    var ret = s.url.replace(/(\?|&)_=.*?(&|$)/, "$1_=" + ts + "$2″);
    // if nothing was replaced, add timestamp to the end

    s.url = ret + ((ret == s.url) ? (s.url.match(/\?/) ? "&" : "?") + "_=" + ts : "");
}

Solution 5

Ajax tools, like jQuery, is able to ask the browser not to cache the requested result, so every request from the loaded web page will travel to web server and get the newest response.

In order to achieve that, set cache flag as false, then an additional query parameter, like _=1234567890, is appended into the request URL. Of course the number is always changing, so the browser thinks it as a brand-new request and won't provide any cached things.

View more solutions

30,264

ZZ Coder

A coder trying to beat a friend on Stackoverflow reputation.

Updated on October 04, 2020

Comments

ZZ Coder over 3 years
I have a PHP server running on Apache, I get lots of request looks like this,
```
10.1.1.211 - - [02/Sep/2010:16:14:31 -0400] "GET /request?_=1283458471913&action=get_list HTTP/1.1" 200 547 0 "http://www.example.com/request" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8 (.NET CLR 3.5.30729)" 28632 15602
```
The _ parameter is mysteriously added to the request. I am trying to find out who is doing that.

There is a NetScaler running in front of Apache.
- RobertPitt almost 14 years
  
  why is the IP 10.1.1.211 that's a local IP provided by a router/modem right?
- jfrobishow almost 14 years
  
  @RobertPitt probably the IP of the NetScaler upstream?
- RobertPitt almost 14 years
  
  oki just wondered, never used NetScaler
ZZ Coder almost 14 years

I do use jQuery but it doesn't appear in every request.
jfrobishow almost 14 years

Are you using some ajax call where you specify the nocache attribute? It will only be added then and only if it's a GET request. See my code below from jQuery if(s.cache === false && type == "GET")
ZZ Coder almost 14 years

I only have this one AJAX call on my page and I do set the nocache attribute. However, some requests don't have the parameter.
theblang over 11 years

This issue in our project at work was caused by $.ajaxSetup({cache:false}) being added to a plugin that was being called.
Kaivosukeltaja about 11 years

Note that the option cache defaults to false if the data type is 'script' or 'jsonp'. api.jquery.com/jQuery.ajax
Tancrede Chazallet about 10 years

Yeah, it just ruined my request to a bank's API which doesn't accept any extra. It was coming from nowhere like "Surprise MotherF#$&@ !" -_-