Site challenge
A site challenge is a check that a website shows to confirm that a visitor is human. Common forms are a CAPTCHA, a puzzle or an "are you human" page. The challenge interrupts automated access, so a program gets a block page instead of the data it asked for.
How site challenges work
A site can run its check in front of its pages or in front of the requests they make. Some checks show a visible test. Others run quietly in the background, such as Cloudflare Turnstile.
A program can tell that it hit a challenge from the response. Typical signals are a 403 or 429 status, a challenge page where data was expected, or a small HTML page with a challenge marker.
Why it matters for AI agents
Challenges are a common reason browser agents fail. An agent cannot prove it is a person, so the honest result is a stop.
Wield and site challenges
When a site shows a check, Wield stops the run with the site_challenge error and asks you to solve the check in your own tab. Wield does not solve bot protection checks, and it does not try to get past them.
In our benchmark, runs of a cloud browser agent were blocked on 10 sites as of 7 November 2026: bahn.de, Lieferando, Zalando, ImmoScout24, Idealo, Eventim, mobile.de, Walmart, Zillow and OpenTable. These results are from our runs, and they are not a claim about every visit. See the benchmark for the method.
Related terms
FAQ
What should an agent do on a challenge?
Stop, and tell the user which site showed the check. The user can solve it in their own browser tab and run the task again. An agent should not try to solve, skip or route around the challenge.
Which sites blocked the cloud browser in your runs?
In our runs, a cloud browser agent was blocked on bahn.de, Lieferando, Zalando, ImmoScout24, Idealo, Eventim, mobile.de, Walmart, Zillow and OpenTable, as of 7 November 2026. The list changes as sites change, so the benchmark holds the current data.
Sources
- CAPTCHA (Wikipedia)en.wikipedia.org
- Cloudflare Turnstiledevelopers.cloudflare.com