API Token: What It Is, Types & Security
What Is an API Token?
An API token is a digital credential a client sends with an API request to prove it can access a specific API or endpoint. It carries defined permissions or scopes and usually has an expiration period.
So, what is an API token in practice? It allows users and applications to access protected resources without repeatedly sending usernames and passwords.
What are API tokens used for? They allow applications, containers, AI agents, CI/CD pipelines, and other services to communicate with APIs and access permitted resources without requiring human intervention for every request.
Unlike passwords that may remain valid for long periods, many API tokens have limited lifetimes and specific permissions. This helps organizations control what each token can access and how long it remains valid.
How API Token Authentication Works
API token authentication works by sending a token with an API request so the server can verify whether the client is allowed to access the requested resource. The token is commonly sent in the Authorization header using the Bearer scheme.
For example:
curl https://api.example.com/users \
-H "Authorization: Bearer YOUR_API_TOKEN"
A successful request may return:
HTTP/1.1 200 OK
Content-Type: application/json
{"users": [...]}
When the server receives the request, it extracts the token and validates it according to the API's authentication mechanism. It checks whether the token is valid, whether it has expired, and whether it provides sufficient permissions.
If the checks succeed, the server processes the request and returns the requested resource.
If the token is missing, expired, or invalid, the server commonly returns a 401 Unauthorized response. A 403 Forbidden response generally means the request is understood, but access is not permitted.
This process allows clients to access APIs without repeatedly sending their login credentials.
API token vs API key
API keys and API tokens are both used to control access to APIs, but they differ in how they identify clients, manage permissions, and handle expiration. The choice depends on the API's authentication and authorization requirements.
Effective API key management involves securely storing, monitoring, rotating, and revoking API keys. API token management also requires organizations to control token permissions, expiration, and revocation.
Neither credential is automatically more secure than the other. What matters is how it is issued, protected, and used.
Types of API Tokens
API tokens serve different purposes depending on how access is granted and managed. Common types include JSON Web Tokens (JWTs), OAuth 2.0 access tokens, refresh tokens, and personal access tokens (PATs).
JSON Web Token (JWT)
A JSON Web Token is a structured token format that can carry information about a user, application, or authorization decision. JWTs are commonly issued by authentication or authorization systems.
A signed JWT typically has three parts:
- Header: Identifies the token type and signing algorithm.
- Payload: Contains claims such as identity, permissions, and expiration.
- Signature: Allows the receiving system to verify the token's integrity and authenticity.
JWTs often include an expiration time, but their lifetime depends on how they are configured.
OAuth 2.0 Access Token
An OAuth 2.0 API access token is issued by an authorization server after an application obtains authorization. The client uses this token to access protected resources.
Access is limited by the permissions granted to the token and the resource server's authorization rules. These tokens are commonly short-lived, although their lifetime depends on the authorization server.
Refresh Token
A refresh token allows a client to request a new access token without requiring the user to authenticate again.
Refresh tokens generally remain valid longer than access tokens and therefore need careful protection. With token rotation, the authorization server can issue a new refresh token whenever the existing one is used, reducing the risk of stolen credentials being reused.
Personal Access Token (PAT)
A personal access token is usually created by a user through a platform or service. It provides programmatic access to APIs, command-line tools, or other supported resources.
PATs may have specific permissions or scopes. Their expiration depends on the platform. Some expire after a defined period, while others remain valid until revoked.
Why API Token Security Matters
API authentication tokens function as digital skeleton keys for your infrastructure. When a token leaks or falls into the wrong hands, attackers gain immediate, automated access to data and systems. OWASP's API Security Top Ten identifies broken authentication and token misuse as primary attack surfaces in modern applications.
The risk extends beyond individual breaches. OAuth security specifications document how token threats like disclosure, manufacture, reuse, and phishing lead to improper access across interconnected systems. Organizations that fail to implement token lifecycle controls face lateral movement, data exfiltration, and compliance violations.
Common Use Cases of API Tokens
API tokens allow applications and services to access protected resources without requiring users to authenticate manually for every request. Common use cases include:
- Cloud services and SaaS: Authenticate service accounts, serverless functions, and container workloads.
- CI/CD pipelines: Access deployment services, secrets, and build APIs.
- Third-party integrations: Allow authorized applications to exchange data through APIs.
- Microservices: Authenticate and authorize communication between services.
- Agentic AI systems: Enable AI agents to access external APIs and data sources within their assigned permissions.
Challenges and Risks of API Tokens
Tokens are widely distributed across code repositories, container images, CI/CD logs, and cloud metadata endpoints. This proliferation creates numerous exposure points. OWASP REST Security guidance notes that API keys alone prove insufficient for high-value access without additional controls.
Real incidents illustrate the operational impact. The Sisense breach required customers to rotate all keys, tokens, and integration credentials after attacker access. A CISA bulletin documented Elasticsearch API keys created with service accounts that granted higher privileges than intended, enabling privilege escalation. CISA vulnerability summaries regularly report tokens accidentally included in client JavaScript bundles and public artifacts.
Attack vectors include extraction from source code, token leakage through logs and error messages, misconfigured cloud metadata endpoints, reuse of long-lived tokens across environments, weak JWT signing algorithms, and overly broad service account privileges.
These incidents show why organizations need to know where their API tokens are stored, who can access them, and whether their permissions are appropriate. Understanding how tokens become exposed is an important part of managing these risks.
How API Tokens Leak?
API tokens can be exposed when credentials are stored, shared, or transmitted outside the systems where they are intended to be used. Sometimes, a developer may accidentally include a token in source code. In other cases, tokens may remain accessible through logs, applications, or unused service accounts.
Here are some common ways API tokens can leak:
Committed to code repositories: Developers may include API tokens in source code, configuration files, or environment files and accidentally push them to shared or public repositories. Anyone with access to those files may be able to retrieve the credentials.
Printed into CI or application logs: Tokens may be recorded in application logs, build outputs, or debugging messages. These records can remain accessible long after the original request has been completed.
Embedded in mobile or front-end code: Tokens included in mobile applications or client-side JavaScript bundles may be extracted by users who can inspect the distributed code.
Pasted into third-party tools or AI agent configurations: Developers sometimes provide credentials to external tools, integrations, or AI agents. If those credentials are stored or handled insecurely, they may be exposed. Research into unsecured API keys highlights the security risks associated with credentials used in agentic systems.
Left on long-lived service accounts: Tokens associated with service accounts may remain active even after they are no longer needed. Without expiration policies, regular reviews, or rotation, these credentials can create unnecessary security risks.
Rotation, Scoping and Revocation
API token management involves controlling how tokens are issued, used, stored, rotated, and revoked throughout their lifecycle. Organizations also need to identify tokens that remain active but are no longer required.
Here are five practices that can help manage API tokens securely.
Apply least-privilege scoping: Give each token only the permissions required for its intended task. Avoid using broad-access credentials when more restrictive permissions are available. Review token scopes whenever applications or service requirements change.
Use short expiry periods: Set token lifetimes based on their purpose and level of risk. Short-lived tokens reduce the time a compromised credential can be used, although they do not prevent misuse while the token remains valid.
Rotate tokens regularly: Establish a rotation schedule based on token sensitivity and usage. Automated rotation can help replace credentials without requiring manual intervention every time.
Revoke exposed tokens immediately: If a token is leaked or suspected to be compromised, revoke it as soon as possible. Issue a replacement, review the activity associated with the exposed credential, and identify how the exposure occurred.
Discover unknown tokens: Organizations also need to identify credentials associated with forgotten applications, service accounts, and other non-human identities. Token Security's non-human identity management platform helps organizations discover non-human identities, establish ownership, and identify associated credentials.
Together, these practices help organisations reduce unnecessary token exposure, limit permissions, and maintain greater control over API access.
Related Terms
- Bearer Token
- JSON Web Token (JWT)
- OAuth Access Token
- Service Account Credentials
- Secrets Management
- Machine Identity
Frequently Asked Questions
What does API token mean?
An API token is a digital credential that allows a user, application, or service to access an API. It is sent with an API request so the receiving system can check whether the client has permission to access the requested resource. API tokens may have specific permissions and expiration periods.
How long should an API token last?
An API token should remain valid only for as long as its intended purpose requires. Short-lived tokens are generally preferred for sensitive operations because they limit the time an exposed credential can be misused.
The appropriate lifetime depends on the application, access requirements, and security risks. Where supported, organizations can use refresh tokens to maintain access without relying on long-lived access tokens.
What happens if an API token is leaked?
If an API token is leaked, anyone who obtains it may be able to access the API using its assigned permissions.
The first step is to revoke the compromised token. Next, issue a replacement and review the systems, resources, and data the exposed token could access. Check the relevant logs for unauthorized activity and address the source of the leak to prevent further exposure.
Why are short-lived tokens more secure?
Short-lived tokens reduce the amount of time a stolen or exposed credential can be misused. Even if an attacker obtains a token, it becomes invalid once it expires. This will restrict the window for unauthorized access. Organizations can pair short-lived access tokens with secure refresh tokens. This helps in maintaining continuous access without relying on long-lived credentials.
What to do if an API token is compromised?
If an API token is leaked, revoke it immediately. Rotate it by issuing a replacement. Then audit what systems and data the compromised token could access. Investigate logs for unauthorized activity. Address the exposure path to prevent it from happening again.
What’s the difference between an API key and an API token?
An API key typically identifies the application or project making an API request and is often long-lived. An API token can represent a user, application, or service and may include specific permissions and expiration controls. API keys are useful for straightforward API access. API tokens such as OAuth access tokens and JWTs support more granular authentication and authorization requirements.
How do organizations prevent tokens from leaking into code repositories?
Organizations can use automated secret-scanning tools to detect API tokens and other credentials in code and commits. Secrets managers keep tokens out of source code by injecting them securely at runtime. Pre-commit hooks and CI/CD security checks can also detect and block exposed credentials before they are pushed to shared or production repositories.
