Headless browser
A headless browser is a web browser that runs without a visible window. A program controls it, usually through the Chrome DevTools Protocol or WebDriver. The program loads pages, clicks, reads content and takes screenshots. The browser renders pages like a normal browser, but no person watches the screen.
How a headless browser works
A program starts the browser with a headless flag, then sends it commands. Tools such as Puppeteer and Playwright do this with Chromium. The browser loads a page, runs its scripts and returns the results to the program.
Chrome has shipped more than one headless mode. The Chrome documentation explains how the current mode works and how it differs from the older one.
Why it matters for AI agents
Cloud browser agents and scrapers often run headless browsers on servers, because no screen is needed. These sessions usually start with no history, no cookies and no logins, and they run from a data center. Sites can often tell such sessions apart from a person's browser, and bot protection often blocks them. An agent that runs in a headless browser may stop at a check page.
Wield and headless browsers
Wield's recipes do not run in a headless browser. They run in the user's everyday browser through the Wield extension, with the user's own session. The extension supports Chrome, Edge, Brave, Arc, Vivaldi, Opera and Chromium.
In our benchmark, the browser-agent side ran Browser Use 0.13.14 with Claude Sonnet 5.5 in a fresh headless Chromium. This was preliminary data as of 7 November 2026. In our runs, bot protection blocked that cloud browser on sites such as bahn.de, Lieferando and Zalando. The benchmark page has the method and the raw rows.
Related terms
FAQ
Is a headless browser detectable?
Sites can detect some differences between headless and regular browser sessions, and bot protection uses those signals. Wield does not try to hide these differences. When a site shows a check, Wield stops and asks the user to solve it in the user's own tab.
What is the difference between old and new headless mode?
Chrome has offered more than one headless mode. The Chrome documentation describes the current mode and the older one it replaced. Read it before you choose a mode for a test or an automation tool.
Sources
- Chrome Headless modedeveloper.chrome.com