What is headless vs headful?
Headless and headful describe whether a browser renders a visible window. A headless browser runs without a graphical interface — lighter, and the common default for automation — while a headful browser renders a full UI like a user’s. Some sites behave differently between the two, and a headful session is easier to watch and record.
Why it matters
For authenticated multi-step workflows, fidelity and observability matter more than shaving milliseconds. It also matters for bot detection: a full desktop profile is one of the things the stealth tier changes when a run is being refused.