A certificate inventory is a complete record of digital certificates, including who owns them, where they are used, and when they expire. In practice, it is a living asset register for TLS, code-signing, authentication, and other trust certificates. It helps security teams answer a basic question: what credentials exist in the environment, and who is responsible for them?
It matters because certificates are often copied across systems, embedded in automation, or left behind after a project ends. Missing inventory creates blind spots during renewal, revocation, migration, and incident response. Defenders use inventories to spot expiring certificates, detect unknown trust chains, and retire credentials safely. Attackers can benefit from the same gaps: a forgotten or orphaned certificate may remain valid long after its owner is gone, allowing unauthorized trust, impersonation, or persistence. Good certificate inventory turns trust management from guesswork into a controlled security process.