What is Mutual TLS (mTLS)?
Turkish: Karşılıklı TLS (mTLS)
Mutual TLS verifies both client and server certificates during a TLS connection, reducing trust in network location alone.
What is Mutual TLS (mTLS)?
Mutual TLS turns standard TLS authentication into a two-sided process. In a normal SSL/TLS connection, the client validates the server certificate. With mTLS, the server also validates the client certificate, so identity is based on cryptographic proof rather than the assumption that traffic came from a trusted network.
During an mTLS handshake, both parties exchange certificate chains, verify that they were issued by a trusted CA, and establish an encrypted session only if validation succeeds. Certificate lifecycle, revocation, short-lived certificates, and automated renewal become operationally important parts of the design.
Where Is It Used?
mTLS is common in service-to-service traffic, B2B APIs, financial integrations, device fleets, and Zero Trust network designs. A service mesh can enforce mTLS between services through central policy, reducing the amount of certificate handling that application code needs to own.
mTLS does not automatically replace every password or API key. In many systems it is combined with authorization scopes, policy checks, and observability. Poor root certificate management, expired certificates, and environment mix-ups can cause outages, so production mTLS requires automation, clear ownership, and an auditable certificate inventory.
Related Terms
A service mesh manages traffic between microservices through a proxy layer, adding mTLS, observability, routing, and policy controls.
SSL/TLS (Secure Sockets Layer / Transport Layer Security)SSL/TLS is the protocol family that provides identity checks, key agreement, and encrypted data transfer between clients and servers.
Zero Trust SecurityZero Trust continuously validates each user, device, and request by identity, context, and permission instead of trusting network location.