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Web Crawler User-Agent: Genuine or Fake?

posted by martyb on Tuesday July 05 2016, @10:51AM   Printer-friendly
from the what-would-you-do? dept.

isj writes:

Disclaimer: I work on a search engine (findx). I try not to put competitors in a bad light.

Question: Should a web crawler always reveal its true name?

Background: While crawling the web I've found some situations where using a fake user-agent might help. First example is a web site that checks the user-agent in the http-request and returns a "your browser is not supported" - even for robots.txt. Another example is a site that had an explicit whitelist in robots.txt. Strangely, 'curl' was whitelisted but 'wget' was not. I hesitate in using a fake user-agent, e.g. googlebot because it isn't clear what the clueless webmasters' intentions are. It appears that some websites are misconfigured or so google-optimized that other/new search engines may have to resort to faking user-agent.

I'm also puzzled by Qwant because they claim to have their own search index but my personal website (which is clearly indexed when I search in qwant) has never been crawled by a user-agent resembling anything that could lead to qwant. Apparently they don't reveal what their user-agent is: https://blog.qwant.com/qwant-fr/. And there has been some discussion about it: https://www.webmasterworld.com/search_engine_spiders/4743502.htm

This is different from search engines that don't have their own index (eg. DuckDuckGo uses results from Yahoo! and yandex. Startpage uses Google, etc.)

So what do you Soylentils say, is faking the user-agent in webcrawls necessary? Acceptable? A necessary evil?

Original Submission

 
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  • (Score: 0) by Anonymous Coward on Tuesday July 05 2016, @12:33PM

    by Anonymous Coward on Tuesday July 05 2016, @12:33PM (#370023)

    Personally I think if a site is returning different content depending on user agent, it's a good idea to make a survey of which pages are affected by requesting the contents of the entire site with every possible user agent in existence. Because this is obviously slow, it can be done in parallel (different ip addresses come also handy if the number of connections is limited). I also recommend redoing the check periodically to see whether the situation has changed.

    It would be great if browsers had this functionality too. They could do it on the background silently and then the results would be already available when you pull out the developer sidebar.