{"json_modified": "2016-08-31T04:13:17.396054", "uuid": "9e64c589-3aad-4e45-a595-15caefecdf8b", "title": "304 Not Modified", "url": "/en-US/docs/Web/HTTP/Status/304", "tags": ["Reference", "HTTP", "Status code", "Redirection"], "translations": [], "modified": "2016-08-31T04:13:17", "label": "304 Not Modified", "localization_tags": [], "locale": "en-US", "id": 192705, "last_edit": "2016-08-31T04:13:11", "summary": "The HTTP <code><strong>304</strong></code><strong><code> Not Modified</code></strong> client redirection response code indicates that there is no need to retransmit the requested resources. It is an implicit redirection to a cached resource. This happens when the request method is <a class=\"glossaryLink\" href=\"/en-US/docs/Glossary/safe\" title=\"safe: An HTTP method is safe if it doesn't alter the state of the server. In other words, a method is safe if it leads to a read-only operation. Several common HTTP methods are safe: GET, HEAD, or OPTIONS. All safe methods are also idempotent as well as some, but not all, unsafe methods like PUT, or DELETE.\">safe</a>, like a <a href=\"/en-US/docs/Web/HTTP/Methods/GET\" title=\"The GET method requests a representation of the specified resource. Requests using GET should only retrieve data.\"><code>GET</code></a> or a <a href=\"/en-US/docs/Web/HTTP/Methods/HEAD\" title=\"The HTTP HEAD method requests the headers that are returned if the specified resource would be requested with an HTTP GET method. Such a request can be done before deciding to download a large resource to save bandwidth, for example.\"><code>HEAD</code></a> request, or when the request is conditional and uses a <a href=\"/en-US/docs/Web/HTTP/Headers/If-None-Match\" title=\"The If-None-Match HTTP request header makes the request conditional. For GET and HEAD methods, the server will send back the requested resource, with a 200 status, only if doesn't have a ETag matching the given one. For other methods, the request will be processed only if the eventually existing resource's ETag doesn't match any of the values listed.\"><code>If-None-Match</code></a> or a <a href=\"/en-US/docs/Web/HTTP/Headers/If-Modified-Since\" title=\"The If-Modified-Since request HTTP header makes the request conditional: the server will send back the requested resource, with a 200 status, only if it has been last modified after the given date. If the request has not been modified since, the response will be a 304 without any body; the Last-Modified header will contain the date of last modification. Unlike If-Unmodified-Since, If-Modified-Since can only be used with a GET or HEAD.\"><code>If-Modified-Since</code></a> header.", "sections": [{"id": "Quick_Links", "title": null}, {"id": "Status", "title": "Status"}, {"id": "Specifications", "title": "Specifications"}, {"id": "Browser_compatibility", "title": "Browser compatibility"}, {"id": "See_also", "title": "See also"}], "slug": "Web/HTTP/Status/304", "review_tags": []}