A self-signed certificate is a digital certificate that is signed by the same entity that created it, rather than by a trusted Certificate Authority (CA). In the context of TLS, this certificate is used to establish an encrypted connection between a client and a server, but it lacks validation from a trusted third-party CA.

While a self-signed certificate can encrypt traffic and ensure that the communication remains private, it does not provide any guarantee that the server is who it claims to be. Without a CA's endorsement, a self-signed certificate is not inherently trusted by clients (such as web browsers). This means that the client cannot automatically verify the identity of the server, and the client will often display warnings when encountering a self-signed certificate. Therefore, industry standards always recommend, when possible, to replace self-signed certificates with CA signed certificates.