Glossary · Scraping & automation
User agent
The string a client sends to identify its browser and operating system, one of the simplest signals a site checks against your IP.
A user agent is a line of text your client sends with every request, naming the browser and operating system it claims to be. Sites read it to decide what to serve, a mobile layout, a supported-browser warning, and automated clients read as automated when the string is missing, generic or obviously a library default.
On its own it proves nothing, because it is trivially editable, which cuts both ways: a scraper can present a convincing browser user agent, and a site knows it can. The signal only becomes useful in combination, checked for consistency against the rest of what the request reveals.
That consistency is the real lesson. A residential IP paired with a default Python user agent is a contradiction a site can spot, and coherence across the address, the user agent and the wider fingerprint matters more than any one of them being perfect.
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