Invalid traffic & fraud
Headless browser
A headless browser is a web browser that runs without a visible window, controlled by code; widely used for testing and scraping, and by bots to fake human visits and ad views.
A headless browser is a real browser engine, often Chrome or Firefox, running invisibly on a machine with no screen. Developers drive it with automation tools to test websites, take screenshots or collect data. Because it renders pages exactly like a normal browser, including running ad code, it is also a favourite tool for bot operators generating fake impressions.
Automated browsers expose clues. The W3C WebDriver standard defines a flag (navigator.webdriver) that signals automation, and headless environments historically differed from real ones in missing plugins, unusual screen sizes, absent fonts, no GPU or odd rendering results. Chrome's newer headless mode is much closer to the normal browser, and bot builders patch many tells, so detection has become an arms race.
Verification vendors therefore combine checks: JavaScript environment probes, graphics and audio rendering device fingerprinting, consistency between the claimed user agent and real capabilities, plus behavioral analysis of interaction. Declared automation from known tools is GIVT; disguised headless bots imitating people are SIVT.
Think of it like this
A headless browser is like a player piano: the keys move and the music plays perfectly, but nobody is sitting on the bench.
An example
A publisher's analytics show 25,000 sessions with a desktop Chrome user agent, a 800x600 screen, no installed fonts beyond defaults and a software graphics renderer: a signature of headless automation on a server.
Related terms
Bot traffic
Bot traffic is visits, ad impressions or clicks generated by automated software rather than people, ranging from honest search crawlers to fraudulent bots built to look human.
Device fingerprinting
Device fingerprinting is identifying or characterising a device from the combination of its technical attributes, such as browser, fonts, screen, graphics and network traits, instead of a stored cookie or ID.
User agent
A user agent is the text string a browser or app sends with each request describing its browser, version, operating system and device, used for compatibility, analytics and fraud detection.
Behavioral analysis
Behavioral analysis in fraud detection is examining how a visitor interacts, such as mouse movements, taps, scrolling, typing rhythm and session timing, to tell real humans from bots and scripted activity.
SIVT (sophisticated invalid traffic)
SIVT (sophisticated invalid traffic) is invalid traffic designed to look human or legitimate, which can only be found through advanced analytics, multi-point corroboration and often human review.
Sources: W3C WebDriver specification, Chrome for Developers: Chrome headless mode, MRC Invalid Traffic Detection and Filtration Guidelines Addendum (2020 update)