- Browser caching
Browser caching (also called HTTP caching) means that a browser stores a copy of a response, such as an image, stylesheet or script, and …
- Cache-Control
Cache-Control is an HTTP header that tells browsers and shared caches such as CDNs whether and for how long they may store a response.
- CDN (content delivery network)
A CDN (content delivery network) is a geographically distributed network of servers that stores copies of a website's files and delivers …
- ETag
An ETag (entity tag) is an HTTP response header that identifies a specific version of a resource.
- HSTS
HSTS (HTTP Strict Transport Security) is a security mechanism that tells browsers to access a host only over HTTPS for a set period.
- .htaccess
.htaccess is a plain-text configuration file for the Apache web server.
- HTTP/2
HTTP/2 is the second major version of the HTTP protocol, standardized in RFC 9113 (the current revision, which replaces RFC 7540).
- HTTP/3
HTTP/3 is the third major version of the HTTP protocol, standardized as RFC 9114 in June 2022.
- HTTP header
An HTTP header is a name-value pair that a client or server sends along with an HTTP request or response to pass extra information, such …
- HTTP Link header
The HTTP Link header is a response header that expresses links between resources, with the same meaning as the HTML <link> element.
- HTTPS
HTTPS (Hypertext Transfer Protocol Secure) is the HTTP protocol sent over an encrypted TLS connection.
- IP address
An IP address is a numeric label that identifies a device or server in a network that uses the Internet Protocol, and it tells other …
- IPv6
IPv6 (Internet Protocol version 6) is the successor of IPv4 and is specified in RFC 8200.
- Last-Modified header
The Last-Modified header is an HTTP response header with the date and time the server believes a resource was last changed.
- Mixed content
Mixed content occurs when a page loaded over HTTPS includes resources, such as images, scripts or stylesheets, that are fetched over …
- Reverse DNS lookup
A reverse DNS lookup (rDNS) is a DNS query that finds the hostname belonging to an IP address.
- Server configuration
Server configuration, in an SEO context, means the settings of a web server such as nginx or Apache that decide how requests are answered.
- Server response time
Server response time is the time a server needs to answer a request.
- SSL/TLS certificate
An SSL/TLS certificate is a digital file that binds a public key to a domain name, so that a browser can check it is talking to the right …
- Vary header
The Vary header is an HTTP response header that lists which request headers influenced the response, so that caches store and serve each …
- Web application firewall
A web application firewall (WAF) inspects the HTTP and HTTPS traffic that reaches a website or web application and blocks suspicious …
- Web hosting and SEO
Web hosting is the infrastructure that serves a website.