Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsAPI security is the practice of protecting application programming interfaces, the logic behind their endpoints, and the data those endpoints expose. It combines controls that establish who is calling an API with checks on what that caller may do, what inputs the API accepts, and how the service behaves under load or attack.
Why API security matters
An API lets software exchange data and request actions. That access can expose sensitive information or business operations, so protecting an API requires more than checking whether a request includes a valid credential. A caller might be authenticated but still try to read another user’s record, invoke an administrative function, or make a costly operation run repeatedly.
OWASP describes API security as strategies and solutions for understanding and mitigating the vulnerabilities and risks specific to APIs. NIST likewise treats API protection as a set of capabilities that includes inventory, authentication, rate limiting, and data analysis.
What are the main API security risks?
The OWASP API Security Top 10 (2023) names ten risk categories. The list is a practical taxonomy, not a claim that every API has all ten weaknesses.
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|---|---|
| API1:2023 Broken Object Level Authorization | A caller can access an object, such as a record identified by an ID, without permission for that specific object. |
| API2:2023 Broken Authentication | Weaknesses in authentication let an attacker impersonate users or otherwise misuse identity controls. |
| API3:2023 Broken Object Property Level Authorization | A caller can read or change object properties they should not be allowed to access. |
| API4:2023 Unrestricted Resource Consumption | Requests can consume excessive computing, storage, or other resources because limits are inadequate. |
| API5:2023 Broken Function Level Authorization | A caller can use functions or operations outside their permitted role. |
| API6:2023 Unrestricted Access to Sensitive Business Flows | Important workflows can be automated or abused in ways the service does not adequately control. |
| API7:2023 Server Side Request Forgery | An API can be manipulated into making server-side requests to unintended destinations. |
| API8:2023 Security Misconfiguration | Insecure settings or deployment choices expose the API to avoidable risk. |
| API9:2023 Improper Inventory Management | Unknown, outdated, or poorly tracked API endpoints create blind spots in security and maintenance. |
| API10:2023 Unsafe Consumption of APIs | An API trusts or processes data from another API without sufficient safeguards. |
Authorization must be checked at the right level
Authorization is a central API security concern. A token can establish a caller’s identity without proving the caller is entitled to access every object or perform every function. OWASP advises: “Object level authorization checks should be considered in every function that accesses a data source using an ID from the user.” In practice, services need checks tied to the requested object and action, not only a broad role or successful login.
How do you secure an API?
API security is a lifecycle responsibility: identify and reduce risks during development, then enforce and monitor controls while the API is running. NIST SP 800-228, published in June 2025, describes capabilities including API inventory, authentication, rate limiting, and data analysis. NIST’s March 13, 2026 update recommends identifying risks in development and runtime and adopting basic and advanced controls incrementally through a risk-based approach.
- Maintain an API inventory. Track endpoints and versions so teams know what is deployed, who owns it, and whether older interfaces remain exposed.
- Authenticate callers. Verify the identity of users, applications, or services before granting access. Authentication establishes identity; it does not replace authorization.
- Authorize every requested action and object. Check whether the caller may perform the specific function and access the specific record or properties involved.
- Validate inputs and constrain their size. Validate query and body parameters, and set maximum lengths for strings, arrays, and request payloads. This reduces malformed-input and resource-exhaustion risks.
- Set resource and rate limits. Limit call frequency and resource use according to the API’s workload and risk. OWASP recommends telling clients the limit and reset time when a limit is exceeded.
- Monitor and respond. Record security-relevant activity, analyze API behavior, detect attacks, and define how the service or operators respond to suspicious activity.
- Build for availability and resilience. Consider throttling, load balancing, health checks, and circuit breakers where the architecture requires them.
These controls should be selected for the API’s data sensitivity, business flows, traffic profile, and deployment model. A public, high-volume endpoint and an internal service carrying sensitive records do not necessarily need identical enforcement.
What does an API gateway do for security?
An API gateway is a common place to enforce controls that apply across multiple APIs. Depending on its capabilities and architecture, it can support authentication and access control, service discovery, load balancing, caching, monitoring, security logging, attack detection and response, health checks, and circuit breakers. NIST SP 800-204 identifies these among gateway and microservices security features.
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NIST notes that API protection products are typically packaged with API gateways, but controls can be centralized or distributed. A gateway can apply shared policies and provide a consistent enforcement point; it should not be assumed to replace endpoint-specific authorization, input validation, or protections inside services. Decide where each control belongs based on the architecture and the risk being addressed.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to compare API security approaches
When evaluating a platform or design, compare the coverage and placement of its controls rather than relying on the label “API security.” NIST notes that “API protection” and “API endpoint protection” are nebulous terms for a set of capabilities, not one universally defined feature.
Quick Recap
- Lifecycle coverage: Does the approach help identify risks during development as well as enforce protections at runtime?
- Control coverage: Does it address authentication, object- and function-level authorization, validation, inventory, rate limiting, monitoring, and response?
- Enforcement location: Which protections belong in the gateway, service code, identity provider, service mesh, or a combination of these?
- Operational depth: Does it provide useful logging, alerting, attack detection, incident response support, and resilience features?
- Fit: Are the controls appropriate for the API’s sensitive data, business workflows, traffic pattern, and deployment model?
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