What does StackOptic analyze?

StackOptic runs 18 analysis modules on any public website from a single URL. It detects 7,000+ technologies (CMS, frameworks, analytics, payments, CDN, hosting), evaluates SSL certificates and HTTP security headers with grades from A+ to F, measures Core Web Vitals (LCP, CLS, TBT, FCP), audits SEO meta tags and structured data, checks email security (SPF, DKIM, DMARC), analyzes AI & LLM readiness including bot access and llms.txt validation, extracts color palettes and typography, estimates carbon footprint, and generates permanent shareable reports.

Does it work on sites behind Cloudflare or bot protection?

Yes. StackOptic uses a real browser engine that loads pages exactly like a human visitor — executing JavaScript, rendering CSS, and handling redirects. This allows it to bypass Cloudflare, LiteSpeed, Sucuri, and other bot protection systems where traditional crawlers and HTTP-only tools fail.

What do I get on the free plan?

The free plan includes 5 analyses per day with access to all 18 modules, full scores, technology detection, and security grades. Every report is permanently accessible via a unique shareable URL — no login required to view. No credit card needed. AI-powered insights, re-analysis, PDF/JSON export, and comparison features are available on Pro ($24/mo) and Agency ($99/mo) plans.

What is AI & LLM readiness analysis?

This module evaluates how visible and citable your website is to AI search engines like ChatGPT, Perplexity, Google AI Overviews, and Claude. It audits access permissions for 8 major AI bots, validates llms.txt and llms-full.txt files, scores citation-ready content structure, and analyzes structured data (JSON-LD) for GEO readiness — helping you rank in the next generation of search.

How long does an analysis take?

Most analyses complete in under 10 seconds. StackOptic runs all 18 modules in parallel using a real browser session, so you get technology detection, security audit, performance metrics, SEO analysis, and AI readiness scoring simultaneously.

How accurate are the results?

Detection is based on real browser execution — DOM inspection, JavaScript runtime analysis, HTTP headers, and DNS records. With 7,000+ technology signatures and Lighthouse-calibrated performance scoring, StackOptic achieves high accuracy for mainstream technologies.

What security checks are performed?

The security module evaluates SSL/TLS certificates, 12+ HTTP security headers (HSTS, CSP, X-Frame-Options, Permissions-Policy, Referrer-Policy), HTTPS enforcement, and email authentication (SPF, DKIM, DMARC). Each site receives a letter grade from A+ to F with specific remediation steps.

Do you store the websites I analyze?

StackOptic only stores publicly available information that any visitor to a website would see — HTML content, HTTP headers, DNS records, and screenshots. We do not access private data, log in to websites, or perform any intrusive testing.

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reactjs.org

https://reactjs.org· First analyzed 13 Feb 2026· Updated 13 Feb 2026

Export

reactjs.org

Mobile

Sponsored

Hosting Provider

Vercel

vercel.com

IP Address

76.76.21.21

Server Location

🇺🇸 Walnut, United States

ASN

AS16509

Organization

Vercel, Inc

Server

Vercel

CDN

Cloudflare

WAF

Cloudflare

Nameservers

rohin.ns.cloudflare.com.joan.ns.cloudflare.com.

Performance

Page Speed

874 KB

60 requests

Image Optimization

Lazy LoadWebPResponsiveVercel Image Optimization

0–49

50–89

90–100

Architecture Stack

Hybrid

⚡ SSG

Frontend

Framework

Next.js

Styling

Tailwind CSS

Infrastructure

Hosting

Vercel

CDN

Cloudflare

Progressive Web App

Web ManifestApple Touch IconTheme Color

Technology Stack

6 Technologies Detected

Analytics

Frameworks

Meta Frameworks

CSS Frameworks

Platforms

SEO Analysis

D58/100

reactjs.orgreactjs.org

React

React is the library for web and native user interfaces. Build user interfaces out of individual pieces called components written in JavaScript. React is des...

Description truncated.

Title Length5 chars

Recommended: 50-60 chars

Description Length260 chars

Recommended: 120-160 chars

Issues (1)

• Many images missing alt text (24/43)

5 issues found

Upgrade to view details

Crawlability

Sitemap

robots.txt

2 rules

Allows all crawlers

Sponsored

Security Score

36%Critical

Interactive

HTTPS

No WAF

89d

Certificate Details

Type

Domain Validated (DV)

Certificate Authority

Let's Encrypt

Key Algorithm

RSA (2048 bit)

Signature

SHA-256 with RSA

TLS Version

TLSv1.3

HTTP Protocol

HTTP/2

Valid From

12.02.2026

Valid Until

13.05.2026

Subject Alternative Names (1)

react.dev

SHA-256 Fingerprint

3B:4F:EC:7E:1C:95:A0:BF:CE:92:3F:EB:15:D7:5F:05:FB:55:64:2F...

Top Recommendations

Security recommendation preview

Upgrade to view recommendations

Upgrade to view header details

HTTP Headers

Developer Console

access-control-allow-origin

age

145222

cache-control

🟡 0s(public, max-age=0, must-revalidate)

content-disposition

inline

content-encoding

⚡ Brotli(br)

content-type

text/html; charset=utf-8

Good Warning Issue

Email Infrastructure

Custom Mail Server

Score

SPF

DKIM

DMARC

Domain Information

reactjs.org

Domain Age

12y 8m

Created

29.05.2013

Expires

29.05.2026

Last Updated

06.03.2025

Registrar

RegistrarSEC LLC

DNSSEC

Not Enabled

Privacy & Compliance

Cookie Consent Banner

GDPR Indicators

Typography & Readability

Optimistic Display

55/100

Readability

/30

32/40

32px · LH 1.38

Hierarchy

/20

20/25

1.62x ratio

WCAG

/25

5/15

Contrast: undefined

Performance

/25

13/20

2 fonts

Heading Font

Optimistic Display

Sans52px

Body Font

Optimistic Display

Sans32px

Contrast Ratio

Reading Comfort

~36 CPL

Needs attention

52px

13px

32px

Major Third

Scale

✅ Excellent readability: 32px body text is ideal for all devices.

✅ Good hierarchy: Clear distinction between headlines and body text.

✅ Good performance: Using 2 font families keeps load times fast.

✅ Consistent design: Single font family with weight variations is a modern best practice.

✅ Smart font loading: Using font-display: swap prevents invisible text during load.

⚠️ Risky: Text appears on background images without overlay protection.

Buy on MyFonts

Business & Marketing Stack

2 Tools Detected

Growing

Behavior Analytics

Google AnalyticsFree

Google Tag ManagerFree

User behavior and product analytics

Sponsored

Scripts & Styles

12 Resources

Scripts

Styles

Async

Defer

Top Script Sources

local(10)googletagmanager.com(1)

Website Identity

reactjs.org

12 years old

RegistrarSEC LLC

Social Profiles

Facebook X (Twitter)GitHub Bluesky

Sponsored

Last analyzed: 13 Feb 2026 at 02:04

Historical Analysis & Change Tracking