metlo
Metlo is an open-source API security platform that discovers API endpoints, detects attacks in real time, and blocks malicious traffic. It includes features for sensitive data scanning, attack context analysis, and automated security testing for OWASP Top 10 vulnerabilities.
Key facts
Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.
| Field | Value |
|---|---|
| Repository | metlo-labs/metlo |
| Owner | metlo-labs |
| Primary language | TypeScript |
| License | MIT — OSI-approved |
| Stars | 1.8k |
| Forks | 105 |
| Open issues | 25 |
| Latest release | v0.1.1 (2023-04-14) |
| Last updated | 2025-07-25 |
| Source | https://github.com/metlo-labs/metlo |
What metlo is
TypeScript-based platform that passively monitors API traffic for endpoint discovery and threat detection, with built-in YAML-based security testing framework and CI/CD integration capabilities. Offers both self-hosted deployment (AWS, GCP, Azure, Docker) and cloud-based attack blocking via detection engine.
Get the metlo source
Clone the repository and explore it locally.
git clone https://github.com/metlo-labs/metlo.gitcd metlo# follow the project's README for install & configurationNeed it deployed, integrated, or customized instead? DEV.co ships production installs.
Best use cases
Implementation considerations
- Deployment claimed at <15 minutes; verify network tap/agent placement for your traffic topology to ensure endpoint discovery capture.
- Sensitive data scanning rules and attack detection models are not detailed in README; review documentation to confirm detection accuracy for your API schema.
- CI/CD integration available but details on supported platforms (GitHub Actions, Jenkins, etc.) not provided—requires documentation review.
- Attack blocking feature depends on cloud connectivity; assess latency and bandwidth overhead of agent-to-cloud communication.
- YAML test framework requires manual test authoring for custom business logic; auto-generated tests cover OWASP Top 10 only.
When to avoid it — and what to weigh
- Zero-Trust or Offline-First Environments — Attack blocking requires agents to communicate with cloud detection engine; not suitable for fully air-gapped or offline-only infrastructure.
- Minimal Deployment Resources — Self-hosted setup requires infrastructure for multiple components (agents, dashboard, backend); lighter-weight edge solutions may be preferable.
- Proprietary API Protocols Only — Designed for HTTP/REST APIs; may have limited utility for gRPC, GraphQL, or proprietary binary protocols without custom extensions.
- Requires Immediate Enterprise Features — User management, role-based access, and advanced attack protection are gated behind enterprise license; open-source tier is limited for multi-team environments.
License & commercial use
MIT License (permissive OSI-approved license). Code redistribution, modification, and private use are permitted with preservation of copyright and license notice.
MIT permits commercial use of the open-source code. However, README explicitly states that user management, role-based access, and attack protection features require an enterprise license. Commercial deployment must either avoid those features or obtain enterprise licensing directly from Metlo. Requires review of enterprise terms before production use.
DEV.co evaluation signals
Editorial assessment — not user reviews. Directional, with an explicit confidence level.
| Signal | Assessment |
|---|---|
| Maintenance | Active |
| Documentation | Adequate |
| License clarity | Clear |
| Deployment complexity | Moderate |
| DEV.co fit | Good |
| Assessment confidence | High |
Do not rely on this vendor's claims of security posture. Key considerations: (1) Attack blocking requires agents to send traffic metadata to cloud; review data privacy terms. (2) Detection models based on "patterns of malicious requests"—efficacy depends on model training and is not independently validated in README. (3) Self-hosted deployment means you own vulnerability patching and security hardening. (4) MIT license carries no security audit or warranty. (5) Sensitive data scanning rules and PII detection logic not described—test on sample workloads. Conduct threat modeling for your API portfolio before production deployment.
Alternatives to consider
Kong API Gateway + Plugins
Mature, open-source API gateway with security plugins (rate limiting, auth, WAF integration); larger ecosystem but requires separate security testing tooling.
AWS API Gateway + WAF
Native AWS service with built-in DDoS protection, authentication, and AWS WAF integration; tightly coupled to AWS but minimal operational overhead.
Commercial SaaS for API security scanning and vulnerability management; higher cost but includes vendor-managed threat intelligence and compliance reporting.
Build on metlo with DEV.co software developers
Review the full documentation, test endpoint discovery on a non-production API, and evaluate enterprise licensing needs before committing to production deployment.
Talk to DEV.coRelated on DEV.co
Explore the category and the services that help you build with it.
metlo FAQ
Can I use the open-source version for a production API without enterprise features?
Does Metlo require me to send all API traffic to the cloud?
What happens if my APIs use non-REST protocols (gRPC, GraphQL)?
How are auto-generated security tests different from manual tests?
Custom software development services
DEV.co is a software development agency delivering custom software development services to companies building on open source. Our software developers and web developers design, integrate, and ship production systems — spanning web development, APIs, AI, data, and cloud. If metlo is part of your open-source observability roadmap, our team can implement, customize, migrate, and maintain it.
Assess Metlo for Your API Security Posture
Review the full documentation, test endpoint discovery on a non-production API, and evaluate enterprise licensing needs before committing to production deployment.