HSTS stands for "HTTP Strict Transport Security," which is a web security policy that aims to increase the security of HTTPS websites.
When a website is accessed over HTTPS, HSTS ensures that the connection between the browser and the server is encrypted and secure, by instructing the browser to only use HTTPS for future requests to the same domain. This helps prevent downgrade attacks where an attacker tries to force the connection to use HTTP instead of HTTPS, which is an insecure protocol.
HSTS works by sending a special HTTP response header, known as the "Strict-Transport-Security" header, which tells the browser to always use HTTPS for a specified amount of time (usually a few months). This ensures that even if the user types the website URL without the "https://" prefix, the browser will automatically use HTTPS to establish a secure connection.
Implementing HSTS is a recommended practice for any website that uses HTTPS, as it provides an additional layer of security against various types of attacks, including man-in-the-middle attacks, session hijacking, and cookie hijacking.