Formatters & Code
Cloudflare Pages _headers Validator
Validate Cloudflare Pages _headers syntax locally. Preview URL matches, combined headers, removals and the limits of Function-generated responses.
Header rules & response preview
Configuration review
| Rule line | URL pattern |
|---|
| Header | Value | Declaration lines |
|---|
Findings
Results
What the result means
Paste your _headers content or load the plain-text file from your project. Enter a sample absolute URL and select whether that response is static, generated by a Function or a redirect. The parser checks rule structure, declarations, limits and repeated headers, then matches the URL without requesting it. Review all matching rules and predicted custom headers together rather than assuming the first rule wins. Placeholder substitutions and removals appear in the local preview. Download a findings report for review, then verify the deployed response yourself. This checker cannot observe redirects, application code, default platform headers or browser enforcement of security policies.
Related tools
Guides
Questions
Why does _headers not affect my Pages Function?
Headers for a Function-generated response must be set in that response. Select the Function response mode to keep this distinction visible in the preview.
Does the first matching header rule win?
Matching rules contribute together. The preview lists all matches and combines repeated attached values, with warnings where multiple declarations need review.
Does this validate my deployed security policy?
No. It reviews configuration syntax and predicts selected static header rules. Browser policy enforcement and the actual deployed response need separate verification.