Is a free security check enough?

It is useful for checking what is visible from the outside, but it cannot find vulnerabilities inside your application. For services that handle personal data or payments, also consider a vulnerability scanner or a paid professional assessment.

What is the difference between a vulnerability scan and a penetration test?

A vulnerability scan checks broadly for known kinds of weaknesses. A penetration test has experts, partly by hand, try to achieve a specific attacker goal.

What does a domain security check look at?

Mainly SPF, DKIM and DMARC against email spoofing, CAA to limit certificate issuers, the SSL certificate, and subdomains visible from the outside. The IDEAVALU check covers SPF, DMARC, CAA and the certificate.

Free Website Security Scanners and Vulnerability Scanners Compared (2026): Which One to Use

By the IDEAVALU team · Updated 2026-10-29

In short: to check a live site's configuration quickly, use a free passive scanner. To find weaknesses inside your web app, run a vulnerability scanner against your own test environment. For production services that handle payments or personal data, hire a professional assessment. This article compares well-known free tools available as of October 2026 by what they check and who they suit.

Security checks versus vulnerability scans

Most free "security checks" are passive scans that use only information anyone can see: the SSL certificate, response headers, DNS settings and other things a browser sees when it opens the page. They put no load on the site and finish in seconds.

A vulnerability scan actually sends attack-like requests to look for weaknesses in forms and login flows. It can find application bugs such as SQL injection and XSS, but you need the site owner's permission. Running one against someone else's site can take their service down or break the law.

A penetration test goes further: experts, partly by hand, try to achieve an attacker's goal such as getting data out.

Free tools compared

Listed from passive checks to vulnerability scanners. Pricing and terms change, so check each official site before you rely on it.

Free website security scanners and vulnerability scanners (checked October 29, 2026)
Tool	Type	What it mainly checks	Sign-up	Best for
IDEAVALU free security check	Passive check	SSL/TLS, HSTS, CSP and other headers, cookies, SPF, DMARC, CAA, and secret API keys in public JS	Required (free)	Indie and AI-built apps on Next.js, Vercel, Supabase and similar stacks
MDN HTTP Observatory	Passive check	HTTP security headers and CSP contents	None	Grading headers in detail against Mozilla's guidelines
SSL Server Test (Qualys SSL Labs)	Passive check	Certificate, supported TLS versions and cipher suites	None	Tuning TLS configuration in depth
Security Headers	Passive check	Presence and grade of security headers	None	A quick look at which headers are present
ZAP (formerly OWASP ZAP)	Vulnerability scan	Sends real requests to test for XSS and other application vulnerabilities	None (open source, runs on your machine)	Developers with their own test environment

Which tool to use

If you are unsure, working through this order leaves the fewest gaps.

Check a site before or right after launch in one go: a passive scanner. For indie or AI-built apps, the IDEAVALU check also searches public JS for secret keys.
Fine-tune headers or TLS: MDN HTTP Observatory and SSL Server Test.
Review email spoofing protection: a domain checker that covers SPF, DKIM and DMARC.
Test logins, forms and APIs for weaknesses: ZAP or similar, against your own test environment. Check the impact before pointing it at production.
Production services with payments or personal data, or a client who asks for a security assessment: a paid professional vulnerability assessment.

Cautions when using free tools

Passing a passive check says nothing about how your login works, your database access control or vulnerable dependencies. Treat the result as a guide to whether the visible configuration is sound.

Use vulnerability scanners only on sites you manage or have the owner's permission to test. Even with passive tools, avoid running them over and over in a short time.

When the IDEAVALU check is a good fit

The IDEAVALU free security check is built for pre-launch checks of indie and AI-built apps. What sets it apart from other free tools: it searches the JS your site sends to browsers for OpenAI, Stripe, Supabase service_role and other secret keys, and it turns every problem into a fix request you can paste into Claude Code or Codex.

It does not test for application vulnerabilities such as SQL injection. Combine it with the other tools in this article as needed.

FAQ

Is a free security check enough?: It is useful for checking what is visible from the outside, but it cannot find vulnerabilities inside your application. For services that handle personal data or payments, also consider a vulnerability scanner or a paid professional assessment.
What is the difference between a vulnerability scan and a penetration test?: A vulnerability scan checks broadly for known kinds of weaknesses. A penetration test has experts, partly by hand, try to achieve a specific attacker goal.
What does a domain security check look at?: Mainly SPF, DKIM and DMARC against email spoofing, CAA to limit certificate issuers, the SSL certificate, and subdomains visible from the outside. The IDEAVALU check covers SPF, DMARC, CAA and the certificate.

Official sources

Written by the IDEAVALU team. Terms of third-party services change, so check the linked pages for the latest information.