opentrap is a free, open-source intercepting proxy positioned as an alternative to Burp Suite, aimed at authorized web application security testing and bug bounty work.

The commercial dominance of PortSwigger Burp Suite in the intercepting-proxy niche has long been a friction point for independent testers and students, and opentrap enters that gap as a self-described free, open-source alternative. The repository positions itself squarely against Burp Suite and, by association, OWASP ZAP, using topics like burp-alternative, intercepting-proxy, and dast to make its intent unambiguous. At roughly 185 stars it is an early-stage project, but one whose framing — AGPL-3.0 licensed, Java-based, community-oriented — signals an ambition to become a serious option rather than a weekend demo.

An intercepting proxy is conceptually simple: it sits between the operator's browser and the target application, terminating and re-originating HTTP and HTTPS connections so every request and response can be paused, inspected, and edited in flight. The hard engineering lives in TLS interception — generating a per-host certificate authority the browser must trust, minting leaf certificates on the fly, and cleanly handling HTTP/2, WebSocket upgrades, and connection reuse. That opentrap is written in Java is a reasonable choice here, since the JVM ecosystem offers mature TLS stacks and HTTP parsing libraries, the same foundation that made OWASP ZAP practical to build and maintain for years.

The topic list the maintainers chose reads like a checklist of the workflow such a tool must support: application-security, appsec, bug-bounty, penetration-testing, web-application-security, and vulnerability-scanner. The presence of vulnerability-scanner and dast alongside http-proxy suggests the project intends to grow beyond passive interception into active analysis — the pattern where a proxy gains a scanner module, repeater-style request replay, and automated crawl-and-audit capability. This is the same trajectory Burp Suite and OWASP ZAP both followed, and it is the natural roadmap for any tool in this category.

One of the most consequential facts about opentrap is its license. AGPL-3.0 is a strong copyleft license that requires anyone offering the software as a network service to publish their modifications, which in practice means cloud vendors cannot quietly fork it into a proprietary SAST/DAST product without releasing source. For an individual operator running it locally during an authorized engagement this is a non-issue, but it tells you the maintainers are deliberately protecting the commons nature of the project, in contrast to the freemium model of the tool it challenges.

For authorized professionals, the practical question is where opentrap fits relative to the incumbents. OWASP ZAP is the established open-source answer, feature-rich but with a UI and architecture that many testers find heavyweight; Burp Suite remains the industry default but gates its most useful features behind a paid license. A new entrant justified its existence by being leaner than ZAP, more open than Burp, and friendlier to plugin or extension development. The topics owasp and owasp-zap in the repo metadata suggest the authors see themselves in dialogue with the OWASP ecosystem rather than ignoring it, which is a healthy sign for standards alignment.

Because the project's README content is minimal at the time of this writing, an evaluation should be grounded in what can be verified directly from the repository. The Java language tag, the main default branch, and the organized topic taxonomy indicate an actively curated project rather than an abandoned dump. Before adopting it in a client-facing engagement, an operator should clone the repository, review the dependency list for outdated or vulnerable libraries — a chronic problem in Java security tooling — and validate its behavior against a lab target such as a deliberately vulnerable test application rather than anything production.

Educational analysis for authorized security professionals. Use only in controlled, authorized environments.

Related coverage

• 3os.org as a shared knowledge base for devops, pentest and sysadmin work


• airecon for autonomous LLM-driven reconnaissance and pentest pipelines


• Dojo-101 for offline-first cybersecurity training and reference