A user-agent string is a piece of information sent by a browser or crawler to a website’s server, identifying what type of client is making the request — such as a specific browser and operating system, or a search engine’s crawler bot like Googlebot.
Analyzing user-agent strings in server logs allows site owners to distinguish genuine search engine crawler traffic from regular human visitors or other automated bots, which is essential for accurate log file analysis.
Some websites use user-agent detection to serve different content to different types of visitors, though this practice (known as cloaking, when done to manipulate search rankings) can carry serious penalty risk if misused.
We analyze user-agent data as part of our Technical SEO log file analysis.