Cloudflare uses browser-based challenges across Challenge Pages, Turnstile, JavaScript Detections (JSD) in Bot Management, and Precursor. This page describes the browser environments that support these checks.
Cloudflare challenges support major desktop and mobile browsers.
The following browsers and environments have limited support and may experience issues.
- Browsers or operating systems that are more than five years old or have not received security updates in over two years.
- Custom or heavily modified browser engines and embedded browsers.
The following environments are not supported.
- Internet Explorer browser.
- Command-line tools such as
wget,curl, or others that lack JavaScript execution capabilities required for Cloudflare Challenges. - Automated browsers are not supported for solving production challenges.
- Browser automation frameworks, such as Selenium, Puppeteer, Playwright, and Cypress, are not supported for solving production challenges. For automated Turnstile testing, use Turnstile test keys.
Browser extensions can interfere with challenges in several ways.
- Ad blockers and content blockers may prevent challenge scripts from loading properly or block communication with Cloudflare's validation servers.
- Privacy-focused extensions like script blockers, fingerprinting protection, or canvas blockers can interfere with the challenge verification process.
- Virtual private network (VPN) or proxy extensions might trigger additional security checks or cause IP address inconsistencies.
Device emulation settings can alter browser signals used by challenges. Results from emulated devices may differ from results on physical devices.
- Mobile emulation in desktop browsers does not reproduce every characteristic of a physical mobile device.
- Browser developer tools can apply network, user-agent, viewport, or JavaScript overrides. Disable these overrides when troubleshooting challenge behavior.
Challenges may behave differently depending on embedded browser contexts.
- WebViews in mobile applications may have limited functionality compared to full browsers
- In-app browsers often have restricted JavaScript capabilities
- Email client preview windows typically cannot complete Interactive Challenges
If your visitors consistently experience challenge issues, refer to Challenge solve issues for additional troubleshooting information.