Browser sniffing

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Browser sniffing is a technology used to detect which internet browser a user is using . As a rule, a browser sends the so-called user agent string in the HTTP header to identify itself to the server. For various reasons, however, a user can modify the user agent string, for example through the setting general.useragent.overridein Mozilla Firefox (user agent spoofing ).

User agent spoofing can be for a number of reasons, including: B. Elimination of compatibility problems (e.g. pretending a desktop browser because there are problems with the mobile version of a website), protection of anonymity but also to bypass user-agent-based page differences , e.g. different prices in the web shop depending on the one used Device.

Despite the possibility of modifying the user agent string, methods have been developed to still recognize the user agent. This is mainly due to the fact that different browsers have different implementations of the Document Object Model (DOM). About special JavaScript it is possible the DOM attributes, and possibly proprietary extensions, such as the only Internet Explorer existing ActiveX to detect. Other general attributes for recognizing the hardware platform ( smartphone , tablet , desktop PC ...) and operating system can be obtained from the dimensions of the screen and the fonts installed. Other technologies such as Java applets or Adobe Flash can reveal platform-dependent details.

Individual evidence

  1. ↑ How to reset the default user agent on Firefox | Firefox Help. In: support.mozilla.org. Retrieved June 3, 2016 .
  2. ^ Thorin Klosowski: How Web Sites Vary Prices Based on Your Information (and What You Can Do About It). In: Lifehacker. Retrieved June 3, 2016 (American English).
  3. ↑ Browser sniffer - a VERY bad thing to rely on! In: www.howtocreate.co.uk. Retrieved June 3, 2016 .
  4. ↑ Panopticlick | About. In: panopticlick.eff.org. Retrieved June 3, 2016 .
  5. ^ Herbert Braun: Web browser fingerprinting: recognizable even without a cookie. In: heise online. January 16, 2017, accessed December 6, 2017 .
  6. ↑ Am I unique? Retrieved December 6, 2017 .