← All Status Codes
304
Not Modified
↪️ Redirection
Info Risk
📖 What Is HTTP 304?
The resource has not been modified since the last request. The client can use its cached version. Saves bandwidth by not retransmitting unchanged resources.
🛡️ Security Implications
Ensure sensitive responses include Cache-Control: no-store to prevent caching. A 304 on authenticated content may leak data if cached by shared proxies.
🔍 Common Causes
Client sent If-Modified-Since or If-None-Match header and the resource has not changed since.
🔧 How to Fix
Set proper Cache-Control headers. Use no-store for sensitive data. Use ETag or Last-Modified for cacheable resources.
🖥️ How to Check
curl -I -o /dev/null -w "%{http_code}" https://example.com