Cloudflare-generated 1xxx errors now return structured JSON when clients send Accept: application/json or Accept: application/problem+json. JSON responses follow RFC 9457 (Problem Details for HTTP APIs), so any HTTP client that understands Problem Details can parse the base members without Cloudflare-specific code. Breaking change The Markdown frontmatter field http_status has been renamed to status. Agents consuming Markdown frontmatter should update parsers accordingly. Changes JSON format. Clients sending Accept: application/json or Accept: application/problem+json now receive a structured JSON object with the same operational fields as Markdown frontmatter, plus RFC 9457 standard members. RFC 9457 standard members (JSON only):
type — URI pointing to Cloudflare documentation for the specific error code status — HTTP status code (matching the response status) title — short, human-readable summary detail — human-readable explanation specific to this occurrence instance — Ray ID identifying this specific error occurrence
Field renames:
http_status -> status (JSON and Markdown) what_happened -> detail (JSON only — Markdown prose sections are unchanged)
Content-Type mirroring. Clients sending Accept: application/problem+json receive Content-Type: application/problem+json; charset=utf-8 back; Accept: application/json receives application/json; charset=utf-8. Same body in both cases. Negotiation behavior
Request header sentResponse formatAccept: application/jsonJSON (application/json content type)Accept: application/problem+jsonJSON (application/problem+json content type)Accept: application/json, text/markdown;q=0.9JSONAccept: text/markdownMarkdownAccept: text/markdown, application/jsonMarkdown (equal q, first-listed wins)Accept: */*HTML (default) Availability Available now for Cloudflare-generated 1xxx errors. Get started curl -s --compressed -H "Accept: application/json" -A "TestAgent/1.0" -H "Accept-Encoding: gzip, deflate" "/cdn-cgi/error/1015" | jq . curl -s --compressed -H "Accept: application/problem+json" -A "TestAgent/1.0" -H "Accept-Encoding: gzip, deflate" "/cdn-cgi/error/1015" | jq . References:
RFC 9457 — Problem Details for HTTP APIs Cloudflare 1xxx error documentation
Fetched April 4, 2026