Non-Authoritative Information
The request was successful but the enclosed payload has been modified by a transforming proxy.
What it means
The HTTP 203 Non-Authoritative Information status response code indicates that the request was successful but the enclosed payload has been modified from that of the origin server's 200 OK response by a transforming proxy (such as a Content Delivery Network or an edge server).
How it works
- 1The origin server responds with a standard 200 OK.
- 2A proxy sitting between the server and the client modifies the response body (e.g., stripping tracking pixels, compressing images, or injecting headers).
- 3The proxy forwards the modified response to the client, but changes the status code to 203 to inform the client of the modification.
Why you're seeing this
- • A proxy modified the response body.
How to fix it
- • Usually no fix is needed, but if the client strictly relies on exact byte hashes (like Subresource Integrity), the validation will fail.
Framework Implementations
Nginx
# Usually configured in Nginx modules when acting as a transforming proxy, not hardcoded.
Real-Life Scenarios
This is almost exclusively used by proxy servers (like CDNs, security firewalls, or caching layers). Application developers rarely return a 203 manually.
Data Loss Prevention Proxies
A corporate firewall intercepts an internal API response, scrubs sensitive PII (like Social Security Numbers) from the JSON, and returns 203 to indicate the data was safely filtered.
HTTP Transaction
1. Client Request
GET /api/v1/internal-docs HTTP/1.1 Host: api.corporate.com
2. Server Response
HTTP/1.1 203 Non-Authoritative Information
Content-Type: application/json
{
"message": "Sensitive info redacted by IT security proxy"
}SEO Implications
Search engines treat 203 identically to 200 OK. They process the provided content.