Glossary
What is a headless browser?
Definition
A headless browser is a browser that runs without a visible interface. Chrome documents a headless mode for servers, containers and CI pipelines, and test tools and bots both use it.
How it works
- A program starts the browser with a headless flag.
- It loads pages, runs scripts and clicks or types through code.
- No person sees the window.
Where it matters
- Headless browsers run page JavaScript, so they can load a CAPTCHA widget.
- CAPTCHAs look for signs of automation, such as a session with no real pointer or key input.
In CaptchaKit
CaptchaKit rejects a game completion that reports no pointer or key interaction as a likely headless client. This is one signal, and a determined attacker can fake input.
Questions
Are headless browsers only for bots?
No. Developers use them for testing and automation.
Can a CAPTCHA detect headless Chrome?
Sometimes, from signals like missing input. A well-built script can hide many of them.
Does headless mean invisible to the CAPTCHA?
No. The page and widget still load and run.
Source
- Chrome for Developers: Chrome Headless mode (checked 2026-10-18)
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