Website validation and testing tools

HTML validation with Nu Html Checker* [+]

Recursive HTML validation with data·yze Website Validator* [+]

CSS validation with W3C CSS Validation Service - Jigsaw* [+]

Link checking with Dr. Link Check* tool (lite edition, max 1500 links)

Link and anchor checking with W3C Link Checker* [+]
Note: Some methods and URI schemes are not supported, and some sites may prohibit the use of the W3C Link Checker. Please keep the recursion level low.

Test for compliance with modern and reliable Internet standards by the Dutch Internet Standards Platform at* [+]

Web accessibility evaluation with WAVE Web Accessibility Evaluation Tool*

Performance evaluation with GTmetrix* [+]

Transport level security evaluation with Qualys SSL Labs Server Test* [+]

HTTP security headers assesment with Security Headers* [+] tool

DNS Security check with DNSSEC Analyzer* [+] by Verisign Labs

Website scanning and analysis with*
When a URL is submitted to, an automated process will browse to the URL like a regular user and record the activity that this page navigation creates.

General security testing with ImmuniWeb Website Security Test*
Checks website for GDPR and Payment Card Industry Data Security Standard technical compliance, security and privacy. Note: ImmuniWeb may get the website location wrong.

Lint HTTP resources with REDbot*
Checks HTTP resources to see how they'll behave, pointing out common problems and suggesting improvements. Although it is not a HTTP conformance tester, it can find a number of HTTP-related issues.

Clicking the [+] fills in the target for the tool automatically.

Last edited March 2021