---
title: JSON responses and RFC 9457 support for Cloudflare 1xxx errors
description: Cloudflare-generated 1xxx errors now return structured JSON when requested with 'Accept: application/json' or 'Accept: application/problem+json', following RFC 9457 (Problem Details for HTTP APIs).
image: https://developers.cloudflare.com/changelog-preview.png
---

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## JSON responses and RFC 9457 support for Cloudflare 1xxx errors

Mar 11, 2026 

[ Cloudflare Fundamentals ](https://developers.cloudflare.com/fundamentals/) 

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) ↗](https://www.rfc-editor.org/rfc/rfc9457), 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 sent                           | Response format                              |
| --------------------------------------------- | -------------------------------------------- |
| Accept: application/json                      | JSON (application/json content type)         |
| Accept: application/problem+json              | JSON (application/problem+json content type) |
| Accept: application/json, text/markdown;q=0.9 | JSON                                         |
| Accept: text/markdown                         | Markdown                                     |
| Accept: text/markdown, application/json       | Markdown (equal q, first-listed wins)        |
| Accept: \*/\*                                 | HTML (default)                               |

#### Availability

Available now for Cloudflare-generated 1xxx errors.

#### Get started

Terminal window

```

curl -s --compressed -H "Accept: application/json" -A "TestAgent/1.0" -H "Accept-Encoding: gzip, deflate" "<YOUR_DOMAIN>/cdn-cgi/error/1015" | jq .


```

Terminal window

```

curl -s --compressed -H "Accept: application/problem+json" -A "TestAgent/1.0" -H "Accept-Encoding: gzip, deflate" "<YOUR_DOMAIN>/cdn-cgi/error/1015" | jq .


```

References:

* [RFC 9457 — Problem Details for HTTP APIs ↗](https://www.rfc-editor.org/rfc/rfc9457)
* [Cloudflare 1xxx error documentation](https://developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-1xxx-errors/)