Nuclei — Vulnerability ScannerNuclei Guide - step-by-step reference to install and use Nuclei, the fast ProjectDiscovery vulnerability scanner. Educational purposes only, online free.FAQ

What is Nuclei?

Nuclei is a fast, open-source vulnerability scanner from ProjectDiscovery. It sends requests to a target based on customizable templates, so you can scan thousands of known weaknesses in seconds.

Is Nuclei illegal?

Nuclei itself is a legal, open-source security tool. Running it against a website or network you do not own or have written permission to test may be illegal. Only scan targets you own or are authorized to assess.

How do I install it?

The easiest way is: go install -v github.com/projectdiscovery/nuclei/v3/cmd/nuclei@latest. Or download the prebuilt binary from the official GitHub releases page and put it on your PATH.

How do I run a basic scan?

Simply run: nuclei -u https://example.com. It auto-downloads the public template packs and starts scanning the target against them, printing matches to the terminal.

What are templates?

Templates are small YAML files that define a check — a request, a matcher, and metadata like the CVE it maps to. Nuclei ships with curated packs (cves, exposures, misconfigurations, etc.) and lets you write your own.

What can it find?

CVEs, exposed files and directories (.git, .env), misconfigurations, missing security headers, open ports via integration, SQLi/XSS indicators and much more — depending on the templates you run.

Is it fast?

Yes. Nuclei is highly concurrent and optimized. A full scan of many templates on one host typically completes in seconds.

What is it good for?

Vulnerability assessment, bug bounty reconnaissance, continuous security scanning in CI, and learning how common web weaknesses look.

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