304 Not Modified

A 304 Not Modified is a type of HTTP status code that tells a browser or search engine: “The content you’re looking for hasn’t changed since the last time you accessed it.” Instead of downloading the same data again, the browser is instructed to load the page or file from its local cache.

This status code is used in the background during everyday web browsing and plays a vital role in improving website speed, performance, and server efficiency.

How it works

When you visit a website, your browser saves certain files like HTML, images, and stylesheets in a local cache. The next time you visit the same page, your browser checks with the web server to see if those files have changed. It does this using a special request called a conditional GET request, often based on headers like If-Modified-Since or ETag.

If the server sees that the content has not changed, it responds with a 304 Not Modified status. That means:

• No need to download the content again.
• The browser can load the version it already has stored locally.
• The page loads faster for the user.
• Less bandwidth is used on the server.

Why is 304 important for SEO and performance?

While 304 responses don’t directly affect SEO rankings, they do play an important role in page speed and user experience, both of which are key ranking factors. Here’s why it matters:

• Faster loading times: Reusing cached resources means faster page loads, which helps reduce bounce rates and increase engagement.
• Efficient crawling: For large websites, 304 responses help search engine bots like Googlebot crawl more efficiently by focusing only on updated pages.
• Lower server load: Since no data is transferred when a 304 is sent, this reduces strain on your server, especially under high traffic.

When do you see a 304 Not Modified?

Users rarely see a 304 directly, since it happens between the browser and server. However, developers and SEO professionals may notice them in tools like:

• Browser developer tools (Network tab)
• SEO crawlers like Screaming Frog or Sitebulb
• Server logs and performance monitoring dashboards

If you see lots of 304 responses in your logs, that’s usually a good sign — it means your caching policies are working well.

How to implement caching with 304 responses

To take advantage of 304 Not Modified, your server needs to support HTTP caching using headers like:

• Last-Modified
• ETag

These headers tell the browser when content was last changed. When a request is made, the server checks these headers and decides whether to return a 200 OK (with full content) or a 304 Not Modified.

In summary, a 304 Not Modified status is a powerful tool for improving website speed and reducing unnecessary server load. While it doesn’t directly impact SEO rankings, it plays a behind-the-scenes role in helping your website perform better — which search engines love.