API Security Testing Tools

Introduction

APIs connect mobile apps, cloud workloads, partner integrations, and internal services. That makes them a favorite target.

Akamai's 2026 survey of 1,840 security decision-makers found that 87% had an API-related incident in the prior 12 months. It's vendor-commissioned, self-reported data, but the direction is clear.

Functional API tests confirm an endpoint returns the right response. They rarely catch authorization failures, exposed data, undocumented endpoints, or business logic abuse.

This guide covers the main tool categories, specific tools worth evaluating, selection criteria, and how to pair automation with expert-led testing.

Key Takeaways

• The right tool depends on your API technology, lifecycle stage, risk profile, and required testing depth.
• API clients, DAST scanners, fuzzers, code analysis, API platforms, and pen tests solve different problems.
• Run continuous automated checks, then add periodic manual testing of authorization and business logic.
• Judge tools on inventory coverage, schema support, alert quality, integrations, and remediation workflow.

What Are API Security Testing Tools and Why Do They Matter?

API security testing tools find weaknesses in API design, implementation, configuration, authentication, authorization, data handling, dependencies, and runtime behavior. Postman describes API security testing as identifying and resolving API vulnerabilities.

That work is distinct from functional testing (does it meet requirements), integration testing (do components work together), and load testing (does it survive peak traffic).

A passing functional test says nothing about whether user A can read user B's data. The OWASP API Security Top 10 (2023) lists the risks that matter most:

• Broken object level authorization (BOLA)
• Broken authentication
• Broken object property level authorization
• Unrestricted resource consumption
• Broken function level authorization
• Unrestricted access to sensitive business flows
• Server-side request forgery (SSRF)
• Security misconfiguration
• Improper inventory management
• Unsafe consumption of APIs

Several of these are separate authorization problems: object access, property access, and function access. Tools that only check whether a token is present miss all three.

Functional collections still help. A Postman collection of authenticated requests can become the backbone of a repeatable security check.

Types of API Security Testing Tools and Capabilities

API Clients and Security Test Collections

Postman and SoapUI let teams build authenticated requests, replay workflows, and script assertions. Postman collections run in CI through Newman or the Postman CLI, using exit codes as pass/fail signals.

SoapUI documents SQL injection, XSS, XML bomb, boundary, and fuzzing scans, though full ReadyAPI security functionality requires a ReadyAPI Test license.

The catch: you write the assertions. These tools don't discover your attack surface on their own.

Schema-Driven Scanners, DAST, and Proxies

DAST is black-box testing of a running application with malicious inputs, no source code needed. API-focused scanners import OpenAPI, SOAP, or GraphQL definitions, then probe live endpoints for injection, misconfiguration, and data exposure.

Common scanners include:

• Burp Suite: Accepts OpenAPI, WSDL, Postman collections, and GraphQL, with limits (Postman input must be v2.1.0; GraphQL scanning requires introspection)
• ZAP: Imports OpenAPI, SOAP, or GraphQL and actively scans endpoints

Fuzzing and Negative Testing

Fuzzers send malformed, boundary, and out-of-sequence inputs. Two MIT-licensed options stand out:

• RESTler (Microsoft): Derives request sequences and producer-consumer dependencies from OpenAPI definitions
• Schemathesis: Generates property-based tests for OpenAPI and GraphQL and chains operations

These tools are strong for input validation, error handling, resource consumption, and surfacing undocumented behavior. Handle with care: RESTler warns that fuzzing can cause outages or corrupt backends.

Code, Runtime, and Dependency Analysis

• SAST analyzes source code, but OWASP notes authentication and access-control problems are hard to automate.
• IAST instruments a running app, so visibility depends on what tests exercise.
• SCA finds vulnerable third-party components.
• RASP protects at runtime, which is not the same as testing.

These supplement API-specific testing. They don't replace it.

Manual Testing and Pen Testing Toolchains

Proxies, clients, and scripts get far more effective in an experienced tester's hands. OWASP guidance covers checks that automation often misses:

• Object-ID manipulation across users
• Low-privilege access to high-privilege functions
• Tenant isolation failures
• Race conditions (for example, concurrent confirmation requests on a payment that should succeed only once)

API Security Testing Tools to Evaluate

General-Purpose Tools

• Postman and SoapUI: repeatable collections, scripted checks, CI execution.
• Burp Suite: request manipulation, authentication testing, API scanning.
• ZAP: proxying and baseline DAST.

ZAP is now independent of OWASP, supported by Checkmarx, and Apache 2.0 licensed. Only the latest full release is supported.

Confirm current features against vendor documentation before buying.

Open-Source Fuzzers

RESTler and Schemathesis suit teams with engineering depth. Expect setup effort, and expect to read raw output rather than polished reports.

Schemathesis adds practical CI-friendly controls:

• Supports rate limits and respects Retry-After after HTTP 429
• Masks tokens in reproduction commands by default
• Exit codes slot into CI

Purpose-Built API Security Platforms

Vendors appear frequently in market coverage, but treat this as a research list, not a ranking. Documentation is uneven. Where a capability isn't stated publicly, ask the vendor.

Platform	Documented highlights
APIsec	OpenAPI/Swagger and GraphQL onboarding; multi-role and tenant validation
Bright Security	DAST for REST, SOAP, GraphQL; business logic stated
Equixly	REST, GraphQL, gRPC; privilege escalation and chained attacks
Akamai (incl. Noname)	Active testing for object access gaps and multistep workflows
Salt Security	Discovery and runtime behavioral detection
Traceable by Harness	REST, GraphQL, SOAP testing; BOLA and business logic
Wallarm	Runtime visibility; AASM adds active vulnerability checks

Ownership has shifted: Akamai completed its Noname acquisition in June 2024, and Traceable merged with Harness in March 2025.

Discovery, Posture, and Runtime Tools

These tool types aren't interchangeable:

• Discovery finds shadow, deprecated, and partner APIs nobody documented
• Posture checks APIs against policy
• Active testing sends traffic to prove exploitability

Salt and Wallarm lean toward discovery and runtime protection, so runtime coverage doesn't prove deep pre-production testing.

Human-Led Testing

Manual API penetration testing validates automated findings and explores what tools can't understand without business context. DeepSeas tests APIs by hand for authentication, authorization, business logic, data exposure, and third-party components. Its testers hold OSCP, OSCE, and OSWP certifications.

How to Choose the Right API Security Testing Tool

Match Coverage to Your API Estate

List every API in scope: public, partner, internal, mobile, microservice, third-party. Check each shortlisted tool against:

• Protocols such as REST, GraphQL, SOAP, gRPC, and WebSockets
• Authentication schemes and deployment environments

Don't assume support. Burp, for instance, rejects Postman file, formdata, and graphql body types, and OpenAPI imports can't contain external references.

Prioritize API-Specific Risk Detection

Ask how the tool tests authorization, not just whether a token exists. Valid credentials can still reach objects and functions they shouldn't. Request evidence for BOLA, property-level and function-level authorization, resource consumption, SSRF, and inventory coverage.

Assess Automation and Safety

Confirm the tool covers:

• CI/CD, gateway, issue-tracker, and SIEM integrations
• Scheduled scans and retesting after fixes
• Large inventories, changing schemas, and rate limits
• Secret storage (Postman Local Vault isn't supported by the CLI or Newman)
• Safe test environments with pre-agreed rules of engagement, as NIST recommends

Evaluate Signal Quality

NIST SP 800-115 says automated findings need validation to isolate false positives. No independent false-positive benchmark exists for these products, so test them yourself.

Ask vendors to show confirmed exploitable behavior, reproducible requests, endpoint-to-owner mapping, and retest verification.

Review Reporting, Pricing, and Ownership

Look for developer-ready findings, executive summaries, audit evidence, role-based access, and data retention. Pricing units vary widely:

• APIsec: per 100 endpoints (path-and-method combinations)
• Equixly: per pen test, or a custom plan with unlimited tests
• Wallarm AASM: free Core and paid Enterprise tiers
• ReadyAPI: requires a Test license for full security features

These units don't compare like-for-like, so get quotes against your actual inventory. Also budget for internal expertise, setup effort, lock-in, and manual testing on top.

How to Implement API Security Testing in Your Program

Establish Inventory, Scope, and Safe Procedures

Build an authoritative inventory that records:

• Owner and environment
• Data sensitivity and authentication method
• Business criticality and dependencies
• Last assessment date

OWASP API9 and NIST SP 800-228 both stress inventory and scheduled discovery.

Then set guardrails:

• Written authorization before testing begins
• Non-production targets where possible
• Protected test credentials
• Rate and payload limits that keep destructive tests off production

Integrate Testing Across the Lifecycle

1. Design and development: spec linting and SAST.
2. Test environments: schema-based scanning and fuzzing.
3. Pre-release: pen testing before high-risk launches.
4. Production: monitoring and recurring assessment.

Make CI gates risk-based. Critical findings block a release; lower-priority issues get tickets. Every finding needs an owner, a deadline, and a retest path.

Combine Automation with Expert Validation

Automation gives repeatable breadth. DeepSeas' offensive security team complements it with manual testing of business logic and authorization.

That work checks cases such as whether changing one identifier returns another customer's records, or whether a workflow can be completed out of order to skip payment or approval. Findings arrive with reproduction steps for developers, a summary for auditors, and retesting to confirm fixes worked.

For compliance, DeepSeas' GRC specialists, including ISO Lead Auditor-certified staff, can tie API findings to risk assessments and audit readiness for SOC 2, ISO 27001, HIPAA, and PCI DSS. That supports your tooling; it doesn't replace it.

Keep a feedback loop running: discover, test, prioritize exploitable risk, remediate, retest, update the inventory, and repeat to catch drift.

Frequently Asked Questions

What is an API security testing tool?

It's software that identifies vulnerabilities in APIs. Depending on the type, it tests code, schemas, live endpoints, dependencies, runtime behavior, or overall API posture.

What tools are used for API security testing?

Main categories are API clients, DAST and proxy tools, fuzzers, SAST/IAST/SCA, API security platforms, and manual pen-testing toolchains. No single ranking fits every environment.

Can Postman be used for API security testing?

Yes, for authenticated requests, collections, regression checks, and scripted tests, including CI runs via Newman. Pair it with scanning, fuzzing, discovery, or manual testing for real coverage.

What is the difference between API security testing and DAST?

DAST is a method: black-box testing of a running application. API security testing is the subject, tailored to schemas, authentication flows, object access, and business logic.

Can automated API security testing replace penetration testing?

No. Automation provides repeatable breadth, but business logic, complex authorization, multi-step workflows, and attack chaining need expert testers. NIST also notes automated findings require validation.

How often should APIs be tested?

Match frequency to release velocity, exposure, data sensitivity, and regulatory duties. PCI DSS requires penetration testing at least every 12 months and after significant changes. Retest after changes to authentication, authorization, or schemas.