APIs are the unsung heroes of modern apps—but they also open doors to attackers. Whether you’re building web apps, mobile backends, or cloud-native services, securing your APIs is non-negotiable.

According to Gartner, 90% of web-enabled apps now have a larger attack surface in their APIs than their UIs. Yet, many APIs still lack basic protections like HTTPS, authentication checks, or proper input validation.

In this article, we’ll cover the top 8 API penetration testing tools every dev or security engineer should know—and how to choose the right one for your stack.

🚨 Why Are APIs So Vulnerable?

APIs connect users to critical data and backend systems. That makes them a high-value target. Common threats include:

  • Broken authentication
  • Injection attacks (SQL, command, etc.)
  • Misconfigured headers or CORS
  • Unsecured endpoints and excessive data exposure

Attackers no longer go through the UI—they head straight for the API. For example, in 2021, Freepik suffered an SQL injection via API that exposed 8.3 million accounts.

If you’re not actively testing your APIs, you’re flying blind.

🛠️ 8 Best API Pentesting Tools in 2025

1. ZeroThreat – AI-Enhanced, Cloud-Based API Pentesting
ZeroThreat is a next-gen pentesting tool for APIs. It runs over 40,000 automated test cases, maps endpoints, and identifies vulnerabilities using AI-generated reports. It supports both modern and legacy APIs with a Zero Trust architecture.

Why Use It:

  • Cloud-native & lightweight
  • CI/CD integration with instant feedback
  • Supports complex auth: JWT, OAuth, MFA
  • 98.9% accuracy with minimal false positives

✅ Ideal for fast-moving teams that need actionable security insights without the noise.

2. Postman Security – Built-in Security for API Developers
Postman isn’t just for testing functionality—it now supports security validations using Spectral and can be used with proxies like Burp or ZAP for dynamic testing.

Features:

  • Static checks for OWASP API Top 10
  • CI/CD pipeline support
  • API monitoring and automated security alerts
  • Easy integration into your existing workflow

✅ Great for dev-first security practices.

3. FireTail – Sensitive Data & PII Protection
FireTail is focused on detecting sensitive data in APIs. It validates API responses, scrubs PII, and integrates with tools like Slack, Jira, and Splunk.

Features:

  • Detects and cleans exposed personal data
  • Policy enforcement for API security
  • Real-time alerting with custom triggers

✅ Best for orgs handling regulated or sensitive data.

4. OWASP ZAP – Open-Source Scanning That Works
ZAP (Zed Attack Proxy) is a classic open-source DAST tool with API support. It works with OpenAPI/Swagger definitions, and offers active/passive scans.

Features:

  • API scanning with authentication
  • Works with SOAP, REST, and GraphQL
  • Integrates into DevSecOps pipelines
  • Fully scriptable for advanced users

✅ Ideal for teams looking for a free, flexible solution.

5. Burp Suite – Powerful Manual API Testing
Burp Suite is an industry standard for manual security testing. While not API-specific, it excels at intercepting and modifying API traffic in real time.

Features:

  • Repeater & Intruder tools for exploit testing
  • Automated scanning with pro version
  • Advanced authentication handling
  • CI/CD plugin support

✅ Perfect for deep, manual assessments of API endpoints.

6. Wallarm – Modern API Threat Protection
Wallarm blends dynamic scanning with runtime protection. It auto-generates OpenAPI specs from traffic, detects bot attacks, and protects against L7 DDoS and credential stuffing.

Features:

  • Secure legacy and modern APIs
  • Real-time threat blocking
  • Supports GraphQL, gRPC, REST
  • GitLab, Jenkins, Selenium integration

✅ Built for DevSecOps teams in large orgs or hybrid cloud setups.

7. 42Crunch – Security from Design to Production
42Crunch is all about "shift-left" API security. It performs static analysis on OpenAPI specs and dynamic testing with randomized inputs.

Features:

  • OpenAPI conformance scanning
  • 300+ security checks
  • CI/CD pipeline integration
  • Real-time scoring and actionable reports

✅ Excellent for teams designing APIs from the ground up.

8. API Secure by Data Theorem – End-to-End Security for Modern Apps
Data Theorem’s API Secure tool scans for vulnerabilities across cloud-native, mobile, and serverless APIs. It auto-discovers APIs and maps threats to compliance standards.

Features:

  • Auth, encryption, availability, and audit checks
  • Shadow API discovery
  • Auto-remediation and real-time alerts
  • Multi-cloud and on-prem support

✅ Great for enterprise environments needing visibility and compliance.

🔎 How to Choose the Right Tool

Before jumping in, consider the following:

  • What types of APIs do you use? (REST, GraphQL, SOAP?)
  • Do you need CI/CD integration?
  • Are you focused on speed, depth, or both?
  • How important is regulatory compliance?
  • Are you testing authenticated flows? (JWT, OAuth, MFA)

Most teams benefit from combining automated tools for baseline testing and manual tools like Burp or ZAP for deep dives.

🔐 Final Thoughts

API attacks are rising—and traditional security tools often miss the mark. Using dedicated API pentesting tools helps uncover blind spots early, reduce attack surface, and ensure secure delivery pipelines.

Whether you're building your first microservice or securing a platform used by millions, investing in the right tool can save you from your next major breach.

🛡️ Start scanning now—before someone else does it for you.