SupportsCSS is a specialized open-source JavaScript library focused on detecting modern CSS feature support in browsers, enabling developers to apply progressive enhancement strategies effectively. The website serves as documentation, demo, and installation guide for the library, targeting front-end developers and web professionals. The site is authored by Stephanie Eckles, a recognized figure in the front-end development community, enhancing its credibility.
Technically, the website is built using the Eleventy static site generator and employs modern web standards including asynchronous JavaScript loading and font preloading for performance. It integrates Plausible analytics for privacy-conscious user tracking. The site is well-structured, mobile-optimized, and accessible, with clear navigation and professional design.
From a security perspective, the site does not expose forms or sensitive data, reducing attack surface. However, it lacks explicit security headers and formal privacy or cookie policies, which are recommended for compliance and trust. No WAF or blocking mechanisms are detected, and no suspicious content is present. Overall, the security posture is adequate but could be improved with standard best practices.
The overall risk is low given the nature of the site as an informational and open-source project resource. Strategic recommendations include adding privacy and cookie policies, implementing security headers, and providing contact channels for security incidents to enhance trust and compliance.
Scanned ·
NIS2 and GDPR posture
GDPR outside view
50/ 100 · Medium
Checks completed
7of 7
NIS2 Art. 21(2)
a(a) Risk analysis and security policies: Not visible from outside
b(b) Incident handling: One indicator
c(c) Business continuity, backups and crisis management: Not visible from outside
d(d) Supply chain security: Not visible from outside
e(e) Secure acquisition, development and maintenance, including vulnerability handling: Partly checked
f(f) Assessing the effectiveness of security measures: Not visible from outside
g(g) Cyber hygiene and security training: Not visible from outside
h(h) Cryptography and encryption: Partly checked
i(i) HR security, access control and asset management: One indicator
j(j) Multi-factor authentication and secured communications: Not visible from outside
Partly checked
One indicator
Not visible from outside
This scan rated NIS2 with an earlier keyword method that is no longer shown; rescan for the per-article view. Risk management, continuity, supply chain, training, MFA, management oversight (Art. 20) and incident reporting (Art. 23) need internal evidence, and Guard cannot tell whether NIS2 applies to this organisation.
GDPR is indicative only, based on publicly visible signals: Articles 7, 12, 13 and 32 of Regulation (EU) 2016/679 and Article 5(3) of the ePrivacy Directive. Not a certification or legal assessment.
Priority findings
7 findings rated critical or high. Fix these first.
Email security
SPF, DKIM and DMARC stop others sending email that looks like it comes from your domain, a common route to phishing and invoice fraud.
Critical
No email authentication configured
Domain is vulnerable to email spoofing
What to do: Implement SPF, DKIM, and DMARC immediately
Security headers
Security headers are instructions your web server sends to every visitor’s browser. Missing ones leave visitors more exposed to attacks such as clickjacking and injected scripts.
High
Missing X-Frame-Options header
Prevents clickjacking attacks
What to do: Add "X-Frame-Options: DENY" or "X-Frame-Options: SAMEORIGIN"
This scan found 22 issues across 6 checks. Monitoring re-runs those checks daily, emails you when something material changes and records each fix, so you can show progress.
Daily monitoring
Recommended
€25per month
TLS certificates and expiry
DNS records
SPF, DKIM and DMARC
Security headers
GDPR and NIS2 posture
Exposed services
Third-party trackers
Security score drift
Email alerts on material changes and an exportable JSON history of every change.
Prices incl. 21% VAT. Secure checkout by Mollie; sold by SEQ SIA, Latvia.
Results by check
Each check with its score, findings and the evidence it collected.
How this score is calculated
The security score runs 0–100, higher is better. It is the plain average of the security checks that completed in this scan, each counted equally. A check that could not run is left out: it counts neither as a pass nor as a fail.
Counted in this score
SSL/TLS
75
Security headers
30
Email security
60
DNS health
75
Network security
100
GDPR outside view
50
Average
65
Not counted
NIS2 outside view: Re-weights evidence from the TLS, email, DNS, network and hygiene checks, so counting it would count that evidence twice. Shown on its own.
OffSeq Observations: An AI reading of the site, useful context but not reproducible evidence. Shown on its own.
Findings that cap the score at 49
Each of these is serious on its own, so while any is present the site cannot rate better than high risk, however good the other checks are.
The certificate is not trusted by browsers
The website is not served over HTTPS
A database, remote desktop, file-sharing or Telnet service is reachable from the internet
The page loads a script from a compromised source
The domain registration has expired
SPF authorises every server to send mail as the domain
Partial scans
When the site blocks Guard or most checks cannot run, the score covers only the checks that ran (usually DNS and email), is capped at 75 and is shown as partial, without a risk level.
Risk levels
Critical0–25
High26–49
Medium50–75
Low76–100
Breach exposure
Leaked credentials and lookalike domains from OffSeq Breach. The counts are free; the detailed lists are paid add-ons.
Dark web exposure
Add-on
Leaked records that mention supportscss.dev, from OffSeq Breach.
No leaked records found
Breach holds no records for supportscss.dev right now. New leaks arrive continuously, so monitoring on Breach alerts you if that changes.
Business context, site observations and technical notes gathered during the scan, and the standards behind each reference.
Business context
Business profile
SupportsCSS occupies a niche market within the web development ecosystem, providing advanced CSS feature detection beyond native CSS @supports capabilities. Its competitive advantage lies in its comprehensive test suite and ease of integration. The business model is community-driven open source with sponsorship and donation support. Target customers are front-end developers seeking cutting-edge CSS support detection. The project demonstrates growth potential through continuous updates and community engagement. Partnerships include GitHub and NPM for distribution, and Plausible for analytics. The author’s personal brand and related projects contribute to the ecosystem and credibility.
Security posture
The website demonstrates a moderate security maturity level appropriate for an informational open-source project. It avoids common vulnerabilities by not including forms or user input fields. However, the absence of security headers such as Content Security Policy, HSTS, and X-Frame-Options is a gap. There is no visible incident response or vulnerability disclosure policy, which could hinder timely handling of security issues. GDPR compliance is not explicitly addressed, and no privacy or cookie policies are present. The use of Plausible analytics indicates a privacy-conscious approach to user tracking. Overall, the security culture appears basic but responsible, with room for formalization and enhancement.
Recommendations
Implement and publish a comprehensive privacy policy and cookie policy to improve compliance and user trust.
Add standard security headers including Content Security Policy (CSP), HTTP Strict Transport Security (HSTS), and X-Frame-Options.
Establish a vulnerability disclosure policy and provide clear contact channels for security incidents.
Enhance GDPR compliance by including explicit user consent mechanisms for tracking and data collection.
Regularly audit third-party scripts and dependencies to ensure no vulnerable libraries are included.
Site observations
Automated reading of the public site. Ratings are indicative.
Business
Company
SupportsCSS / Stephanie Eckles
Description
SupportsCSS is a JavaScript library for live, in-browser detection of modern CSS support for selectors, features, and at-rules. It helps developers apply support-based classes and expose results objects for easier progressive enhancement and feature detection beyond CSS @supports capabilities.
Key services
Feature detection for modern CSS selectors, properties, and at-rules, Support-based CSS class injection, Custom test addition, JavaScript API for querying CSS support
Content quality
excellent
Branding
consistent
Technology
Stack
JavaScript, CSS, HTML
Frameworks
Eleventy v3.0.0
Performance
fast
Mobile
excellent
Accessibility
good
SEO
good
Security
Observed score
70/100
Good practices seen
No forms or inputs detected
No sensitive data exposure in HTML
Analytics and tracking
Services
plausible.io
Tracking level
minimal
Privacy practices
basic
Advertising
Tracking pixels
plausible.io
Marketing tools
plausible.io
Transparency
basic
Site quality
Design
excellent
User experience
excellent
Content relevance
excellent
Navigation
excellent
Professionalism
excellent
Trustworthiness
high
Key observations
Website is a technical documentation and demo site for SupportsCSS library.
No privacy, cookie, or terms of service policies found.
No contact emails or phone numbers explicitly provided.
Social media link to Mastodon profile of the author present.
Uses modern JavaScript and CSS techniques with Eleventy static site generator.
Includes Plausible analytics for minimal tracking.
No forms or user input fields detected.
No explicit security headers or policies visible in HTML content.
No signs of suspicious or malicious content.
Technical notes
Notes
The website is built on a modern static site generator (Eleventy v3.0.0) and uses contemporary web technologies such as asynchronous JavaScript loading, font preloading, and modular JavaScript imports. It integrates Plausible analytics for lightweight, privacy-focused tracking. The site is performant, mobile-optimized, and accessible with semantic HTML structure. There is no detected CMS or dynamic backend. Hosting details are not explicit but likely static hosting. No technical debt or deprecated technologies are evident. Opportunities exist to improve security headers and formalize privacy compliance. Overall, the technical implementation is robust and well-suited for the site’s purpose.
Standards and sources
Reference chips under each finding point to the standard, regulation or specification the finding relates to. They are taken from the official datasets below and mapped conservatively: a finding with no defensible link shows none. NIS2 and GDPR references mark where a finding is relevant evidence, not a compliance verdict. Implementing Regulation (EU) 2024/2690 binds digital infrastructure and digital service providers; for other entities it is the most detailed public reading of the Article 21 measures. WCAG, EN 301 549, European Accessibility Act and Web Accessibility Directive references name the requirement an automated accessibility rule relates to; they are not a conformance verdict.
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