Client ID And Secret

A Client ID and Secret are application credentials used to identify and authenticate an API integration. Together they establish the client’s trust relationship with the service, but they do not replace proper authorization controls. Because they are sensitive credentials, they must be stored securely and rotated when exposure is suspected.

Expanded Definition

client id and secrets are the basic credential pair most commonly used by applications, services, and automated workflows to prove an integration’s identity to an API or authorization server. The client ID is typically public and acts as a lookup identifier, while the client secret is confidential and must be treated like any other sensitive secret. Together, they support client authentication, but they do not grant permissions on their own and they do not remove the need for scopes, policy checks, or token-based authorization.

Definitions vary across vendors in how tightly they separate “authentication” from “registration,” but the security expectation is consistent: the secret must remain private, be rotated, and be protected in a secrets manager or equivalent control. In identity-heavy environments, these credentials are part of the broader Non-Human Identity surface described in the OWASP Non-Human Identity Top 10, especially where machine-to-machine trust is long-lived or widely distributed. The most common misapplication is treating the client secret as an authorization mechanism, which occurs when teams assume possession of the secret alone is enough to permit access to sensitive APIs.

Examples and Use Cases

Implementing client ID and secret rigorously often introduces lifecycle overhead, requiring organisations to balance integration simplicity against secret handling, rotation, and exposure response.

• A SaaS application uses a client ID and secret to obtain access tokens from an authorization server before calling a protected API.
• A backend job in a CI/CD pipeline authenticates to a deployment platform with a stored secret, then exchanges it for short-lived credentials.
• An internal service uses the credential pair to register with an identity provider, but access is still constrained by token scopes and policy decisions.
• A security team stores the secret in a managed vault rather than in source code, environment files, or chat systems, reducing accidental disclosure risk.
• An incident response workflow rotates the secret immediately after suspected exposure, then reviews logs for unauthorized token issuance and unusual API calls.

For machine-to-machine systems, the operational model is closely related to NHI governance: the OWASP Non-Human Identity Top 10 highlights why these credentials need inventory, ownership, and continuous oversight. In practice, the secret often becomes one piece of a broader trust chain that includes token exchange, workload identity, and downstream access control.

Why It Matters for Security Teams

Client IDs and secrets matter because they are frequently the first credential pair introduced into application ecosystems, and also the easiest to mishandle at scale. Once leaked, they can enable unauthorized token requests, service impersonation, credential stuffing against APIs, or silent abuse that looks like normal integration traffic. Security teams need to understand that the problem is not simply “a secret exists,” but that the secret represents a persistent trust relationship that must be governed like an identity asset.

This is where identity security, NHI management, and API protection converge. A secure design usually pairs the credential with narrowly scoped authorization, monitoring, and rotation policies, while reducing blast radius through shorter-lived tokens and stronger workload identity patterns. Guidance in frameworks such as NIST SP 800-63 reinforces the need to distinguish identity proofing and authenticator strength from downstream access decisions, while OWASP Non-Human Identity Top 10 captures the governance gap around non-human credentials. Organizations typically encounter the true cost of client secrets only after a repository leak or production token abuse, at which point rotation, revocation, and dependency tracing become operationally unavoidable to address.

Related resources from NHI Mgmt Group

• How should security teams implement Client ID Metadata Documents?
• When should organisations choose private_key_jwt over a client secret?
• Why does PKCE matter if a client already has a secret?
• How should security teams replace shared-secret OAuth client authentication in production?