The reason why your SSL certificate is self-signed is because it has not been issued by a recognized Certificate Authority (CA). A self-signed certificate is essentially one that you generate and sign yourself, without involving a trusted third-party CA.
There are a few reasons why you might choose to use a self-signed certificate. One reason could be that you are setting up a development or testing environment where security is not a primary concern. In such cases, using a self-signed certificate can be a quick and easy way to enable HTTPS without the need to purchase a certificate from a CA.
Another reason could be that you are running a small personal website or blog, where the cost of obtaining a certificate from a CA may not be justifiable. In such cases, a self-signed certificate can still provide encryption for your website, even though it may not be trusted by all browsers.
However, it is important to note that self-signed certificates are not trusted by default by most web browsers and operating systems. When a user visits a website with a self-signed certificate, they will typically see a warning message stating that the connection is not secure or that the certificate is not trusted.
This warning is displayed because the browser does not have any way to verify the authenticity of the self-signed certificate. Without the involvement of a trusted CA, there is no way for the browser to confirm that the website is who it claims to be.
To mitigate this issue, you can manually install the self-signed certificate on the devices that will be accessing your website. This allows the browser to trust the certificate and establish a secure connection without any warning messages. However, this approach is not practical for large-scale deployments or public-facing websites, as it would require installing the certificate on every device that accesses the site.
In contrast, a certificate issued by a trusted CA is automatically trusted by browsers and operating systems. This is because the CA has gone through a verification process to confirm the identity of the website owner and ensure that they are a legitimate entity. When a browser encounters a certificate issued by a trusted CA, it can validate the certificate and establish a secure connection without any warning messages.
The main reason why your SSL certificate is self-signed is because it has not been issued by a trusted CA. Self-signed certificates can be useful in certain situations, such as development or personal websites, but they are not trusted by default by most browsers. If you require a certificate that is trusted by all browsers, you will need to obtain one from a recognized CA.