HTTP 304 Not Modified

What it means

Not Modified describes how the server processed the request and what the client should do next.

Why it happens

Common triggers include protocol conditions, routing decisions, and application behavior.

Common causes

• Resource moved to a different URI
• Canonicalization or routing rule
• Caching or method-preservation choice

How to fix it

• Confirm redirect destination and protocol
• Prevent redirect chains/loops
• Use the correct permanent vs temporary code

Example request/response

GET /example HTTP/1.1
Host: errorlookup.com

HTTP/1.1 304 Not Modified

Browser/dev/server context

Use browser network tools, server logs, and APM traces together when diagnosing HTTP 304.

Related status codes

FAQ

Is HTTP 304 officially assigned?

Yes. This code is assigned in the IANA registry.