TL;DR, What is Nuclei?
Nuclei is a fast, open-source vulnerability scanner built for modern DevSecOps. While traditional scanners often struggle with false positives and slow, rigid methods, Nuclei solves these problems with a flexible, template-driven architecture. Using simple YAML files, Nuclei performs direct behavioral checks and validation logic to confirm exploitability, which reduces false positives.
The scanner provides accurate coverage across web applications, network services, and cloud infrastructure, helping your team scale vulnerability assessments without losing accuracy. Developed by ProjectDiscovery, Nuclei gets its strength from a community-driven template ecosystem, with over 11,000 contributions from researchers worldwide to ensure quick coverage of new threats.
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At-A-Glance
GitHub: https://github.com/projectdiscovery/nuclei
License: MIT
Primary Language: Go
Stars: 25k ⭐
Last Release: August 2025
Topics/Tags: security-scanner, vulnerability-assesment, cve-scanner, dast
Common use cases
Developers embed Nuclei into automated CI/CD pipelines to run security regression tests on new code. Doing so helps ensure that releases don't introduce known vulnerabilities into staging or production environments.
Security researchers use Nuclei to quickly list and test large attack surfaces for common vulnerabilities. They also create custom templates to scale unique findings across thousands of targets.
Security operations teams deploy Nuclei to continuously scan externally exposed assets and cloud infrastructure. A continuous scan helps ensure compliance with security policies and finds misconfigurations before an attacker can exploit them.
Incident response teams use Nuclei with custom or community templates to quickly assess the organization's exposure, which helps prioritize patching and manage risk.
Analysts use Nuclei's matching capabilities to validate findings from other scanners. Nuclei's validation helps filter out false positives and confirm exploitability, allowing teams to focus on actionable threats.
How does Nuclei work?
Nuclei operates on a straightforward principle. You provide targets, like URLs or hosts, and select specific YAML templates that define security checks. The core Nuclei engine then handles the entire process. For each target-template pair, the engine crafts the necessary requests (HTTP, DNS, etc.), sends them to the target, and analyzes the response to find potential vulnerabilities before exporting the findings.
Template-Driven Logic: The Template Engine at the core of Nuclei depends on simple YAML files. Those templates contain all the logic for crafting requests and defining the exact criteria for a successful match, such as specific status codes, regex patterns, or content length.
Matching: Once a response comes in, the Matcher System performs a detailed analysis using a variety of techniques—from simple text matching to XPath queries and binary data validation.
Parallel Execution: Nuclei is built for speed. The Go-based engine manages concurrent scanning across many targets at once, while respecting the rate limits you set to avoid overwhelming target systems. This design works well for both smaller, and large-scale scan operations.
Core Capabilities:
1. Nuclei uses a human-readable YAML template system that standardizes vulnerability detection logic. The accessible format helps speed up development and community contributions. A repository of over 11,000 ready-to-use templates, with automatic updates ensuring coverage for the latest CVEs and misconfigurations, make Nuclei a very powerful community-driven framework for security checks.
2. Nuclei supports a wide range of protocols beyond the scope of typical web scanners, including HTTP/S, DNS, TCP, TLS, and headless browser automation. This support allows your security team to assess web applications, network services, APIs, and cloud infrastructure with a single tool across different technology stacks.
3. The tool features a matching engine that reduces false positives. The engine uses boolean logic (AND/OR) to combine multiple matchers—such as status codes, headers, and body content—to validate vulnerabilities with precision. The matching process helps ensure reported findings represent real, exploitable conditions.
4. Built in Go, Nuclei is designed for speed and efficiency. It uses concurrency to scan thousands of targets at once. The engine includes configurable rate limiting, intelligent retries, and optimized network handling, allowing it to perform large-scale assessments of enterprise infrastructure in minutes.
5. Nuclei integrates into modern workflows like CI/CD pipelines and security orchestration platforms. It supports multiple output formats like JSON and SARIF for compatibility with other tools. Features like webhook notifications and API-driven automation make the tool a good fit for DevSecOps practices and large security programs.
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Limitations
1. The scanner's effectiveness depends on the quality and accuracy of its templates. Nuclei can miss vulnerabilities if a relevant template doesn't exist or is flawed.
2. While basic templates are simple, writing complex, multi-stage logic for custom applications requires a deep understanding of Nuclei’s syntax and the target technology, which can present a steep learning curve for new users.
3. Nuclei's concurrent scanning engine can generate intense traffic. If you don't configure it with appropriate rate limits, the traffic could disrupt sensitive applications or trigger network defenses.
4. As an automated tool, Nuclei is good at finding known patterns but cannot discover complex business logic flaws or new vulnerabilities that require human creativity and context.
5. To perform authenticated scans or assess internal assets, you need to configure Nuclei with secure credential management and network access. This process can be complex and may introduce operational risks if mismanaged.
While Nuclei excels at fast, template-based vulnerability scanning, prioritizing its findings can be a challenge. That’s where you can pair Nuclei with Wiz. Wiz ingests your scan data and adds critical cloud context, showing you which vulnerabilities expose sensitive data or are actually exploitable through a real attack path. This helps you focus on fixing the risks that truly matter.
Getting Started:
Step 1: Make sure you have Go 1.23+ installed on your machine.
Step 2: Install Nuclei by running:
go install -v github.com/projectdiscovery/nuclei/v3/cmd/nuclei@latestStep 3: Add the Go bin directory to your PATH if you need to, so you can run Nuclei from any location.
Step 4: Check the installation and see the available options:
nuclei -hStep 5: To run your first scan, try:
nuclei -target https://example.com