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codecrafters.io

https://codecrafters.io· First analyzed 25 May 2026· Updated 25 May 2026
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codecrafters.io
Desktop screenshot of codecrafters.io
Mobile screenshot of codecrafters.io
Mobile

Sponsored

Hosting Provider

Vercel
vercel.com

IP Address

216.150.1.1

Site Location

🇺🇸 United Statesvia ip

Server Location

🇺🇸 Walnut, United States

ASN

AS16509

Organization

Vercel, Inc

Server

Vercel

Nameservers

ns1.digitalocean.com.ns2.digitalocean.com.ns3.digitalocean.com.

Performance

100

Core Web Vitals

Weight

First Contentful Paint
546 ms10%
Speed Index
710 ms10%
Largest Contentful Paint
—25%
Total Blocking Time
0.0 ms30%
Cumulative Layout Shift
0.00025%
675 KB
86 requests

Image Optimization

Lazy LoadResponsiveVercel Image Optimization
0–49
50–89
90–100

Architecture Stack

Hybrid
🔀 Hybrid
Frontend
Framework
Next.js
Styling
Tailwind CSS
Infrastructure
Platform
Vercel
CDN
Vercel Image

Technology Stack

8 Technologies Detected

Analytics

3
Google Analytics
Google Analytics 4
PostHog

Meta Frameworks

1
Next.js

CSS Frameworks

1
Tailwind CSS

Tag Managers

1
Google Tag Manager

Platforms

1
Vercel

CDN

1
Cloudflare

SEO Analysis

A81/100
25
4
0
Meta Tags13/15
Content10/12
Headings8/8
Technical22/25
E-E-A-T2/7
Images5/7
Links5/5
URL5/5
Social4/5
Freshness0/4
Mobile4/4
Indexability3/3
C
codecrafters.iocodecrafters.io

CodeCrafters | The Hardest Programming Challenges on the Internet

Build your own Redis, Git, SQLite, and more from scratch. Advanced challenges designed for experienced engineers, used by developers at Google, OpenAI, and V...

Description truncated.
Title Length65 chars

Recommended: 50-60 chars (~397px / 580px)

Description Length163 chars

Recommended: 120-160 chars

Issues (0)

    4 issues found

    Upgrade to view details

    Crawlability

    Sitemap

    Type: standard

    32 URLs

    robots.txt

    4 rules

    Sitemap reference found

    Local SEO

    Local Search Readiness

    14/100
    Poor
    4 13

    This site doesn't appear to be a local business. Local SEO signals are optional for non-local websites.

    Sponsored

    AI & LLM Readiness

    D51/100
    Bot Access
    20/25
    Machine Read.
    13/25
    Schema Data
    6/25
    Citation
    12/25

    AI Bot Access

    14/14 accessible
    AI Search
    OAI-SearchBot
    PerplexityBot
    Claude-SearchBot
    Gemini-Deep-Research
    DuckAssistBot
    Training
    GPTBot
    ClaudeBot
    Google-Extended
    Meta-ExternalAgent
    Bytespiderinfo
    Amazonbot
    Applebot-Extended
    CCBotinfo
    Fetch
    ChatGPT-User

    Machine Readability

    llms.txt
    llms-full.txt
    Semantic HTML
    Heading Hierarchy
    nav
    Text ratio:3%
    Words:1,406
    Token eff.:Optimal
    Sections/1K:1.4
    Depth:1/5

    Structured Data

    1 JSON-LD
    Person×1.3Organization×1.1
    sameAs entity links

    Citation Readiness

    Opening Summary13w
    Descriptive Headingsavg 2.4w
    Canonical URL
    Open Graph3/3
    Twitter Card3/3
    Language Tag
    Publish Date
    Author Info
    Lists
    Tables
    TL;DR / Summary
    About Page Link
    Recommendations (7)
    AI readiness recommendation preview...
    Upgrade to view recommendations

    Sponsored

    Accessibility

    WCAG 2.1 Compliance

    Evaluates how accessible your website is for users with disabilities, based on WCAG 2.1 guidelines. Checks images, forms, keyboard navigation, ARIA roles, and color contrast.
    A
    87/100
    14
    Passed
    0
    Critical
    0
    Warnings
    Images & Alt Text
    20/20
    Checks if images have descriptive alt text for screen readers and visually impaired users.
    Semantic Structure
    20/20
    Evaluates proper use of HTML5 semantic elements (header, nav, main, footer) and heading hierarchy.
    Forms & Inputs
    15/15
    Verifies form fields have labels, error messages are clear, and inputs are properly associated.
    Color & Contrast
    15/15
    Tests text-to-background color contrast ratios against WCAG AA/AAA minimum requirements.
    Keyboard & Focus
    13/15
    Ensures all interactive elements are reachable and operable via keyboard (tab, enter, escape).
    ARIA & Roles
    4/15
    Checks correct use of WAI-ARIA attributes (roles, states, properties) for assistive technologies.

    Carbon Footprint

    SWDM v4 · Eco-Score

    Carbon emissions estimated using the Sustainable Web Design Model v4 (SWDM v4). Factors in data center, network, and device energy across new and returning visitors. Grade thresholds based on HTTP Archive percentiles.
    79/100
    A
    68 mg
    CO₂e / view
    674.7 KB
    Page Weight
    80%
    Cleaner Than
    New Visitor
    78 mg
    vs
    Returning (cached)
    39 mg
    Annual (10K/mo)
    8.2 kg
    Emission Segments
    Data Center
    3 mg
    Network
    20 mg
    Device
    45 mg
    Resource Breakdown
    JavaScript
    343.9 KB
    Images
    106.8 KB
    CSS
    13.5 KB
    Fonts
    141.9 KB
    HTML
    23.0 KB
    Other
    45.5 KB
    Green Hosting Verified
    Vercel
    Provider Match
    2 recommendations
    • •Carbon footprint recommendation preview...
    Upgrade to view recommendations
    A+

    Security Score

    93%Excellent
    Static / Informational

    HTTPS

    No WAF

    81d

    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

    16.05.2026

    Valid Until

    14.08.2026

    Subject Alternative Names (1)

    codecrafters.io

    SHA-256 Fingerprint

    A0:77:74:95:D8:1E:65:29:38:15:22:99:34:24:33:38:D6:F6:5C:1B...

    Recommendations

    Security recommendation preview

    Upgrade to view recommendations
    Upgrade to view header details

    HTTP Headers

    Developer Console

    access-control-allow-origin
    *
    age
    153952
    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

    Google Workspace

    Score

    90

    SPF
    DKIM
    DMARC

    DMARC Policy

    None (Monitor Only)

    MX Records (5)

    alt2.aspmx.l.google.com
    alt3.aspmx.l.google.com
    aspmx.l.google.com
    alt1.aspmx.l.google.com

    +1 more

    Domain Information

    codecrafters.io

    Domain Age
    6y 6m

    Created

    12.11.2019

    Expires

    12.11.2026

    Last Updated

    16.11.2025

    Registrar

    Gandi SAS

    DNSSEC
    Not Enabled

    Privacy & Compliance

    Cookie Consent Banner
    Privacy Policy
    Terms of Service

    GDPR Indicators

    Privacy policy page linked

    Mobile Compatibility

    Viewport & Responsive Test

    Tests how well your website works on mobile devices. Checks viewport configuration, responsive layout, touch targets, font readability, and simulates rendering across different screen sizes.
    C
    68/100
    Mobile Friendly
    Viewport Meta
    The viewport meta tag tells mobile browsers how to scale the page. Without it, mobile devices render at desktop width.
    Responsive Design
    Uses CSS media queries or flexible layouts to adapt content to different screen sizes automatically.
    Touch Icons
    Apple touch icons and favicons displayed when users add the site to their home screen on mobile devices.
    Readable Font Size
    Base font size should be at least 16px on mobile to ensure text is readable without zooming.
    Relative Units
    Using em, rem, %, or vw instead of fixed px values allows content to scale properly across screen sizes.
    No H-Scroll Risk
    No elements wider than the viewport that would cause horizontal scrolling on mobile devices.
    Tap Targets OK
    Interactive elements (buttons, links) are at least 48x48px with enough spacing to prevent accidental taps.
    No Fixed Widths
    No elements with fixed pixel widths that could overflow on smaller screens and break the layout.
    Viewport
    width=device-width, initial-scale=1
    2 recommendations
    • •Mobile compatibility recommendation preview...
    Upgrade to view recommendations

    Typography & Readability

    Source Serif 4 + PP Neue Montreal

    WCAG Partial
    67/100
    Readability
    /30
    14/30

    12px · LH 1.67

    Hierarchy
    /20
    17/20

    5.67x ratio · ✓ H1→H6

    WCAG
    /25
    16/25

    1:1 min contrast

    Performance
    /25
    20/25

    2 fonts · 3 req

    Heading Font

    Source Serif 4

    Serif68px

    Body Font

    PP Neue Montreal

    Sans12px

    Contrast Ratio

    1:1

    33 issues

    Reading Comfort

    ~44 CPL

    Narrow lines
    68px
    h1
    40px
    h2
    14px
    h3
    12px
    p

    ❌ Critical: 12px body text is too small. Minimum 14px, recommend 16px+.

    ⚠️ Partial contrast: 33 elements below WCAG AA threshold (min 1.0:1).

    ✅ Perfect heading hierarchy: Sequential h1→h2→h3 with single H1 — ideal for SEO & accessibility.

    ✅ Strong hierarchy: Headlines are 5.7x larger than body text.

    ✅ Lean font stack: 2 font families keeps load times fast.

    ✅ Smart font loading: font-display: swap prevents invisible text during load (FOIT).

    Buy on MyFontsFlesch 59

    Color Palette

    3 unique colors
    Dark
    #667478
    Secondary· 5.7%
    #081418
    Primary· 91.7%
    #040508
    Primary· 2.6%

    Business & Marketing Stack

    3 Tools Detected

    Advanced

    Customer Support

    1
    Help ScoutSMB

    Live chat and helpdesk tools

    Behavior Analytics

    2
    Google Tag ManagerFree
    Google AnalyticsFree

    User behavior and product analytics

    2

    Categories

    3

    Total Tools

    0

    Enterprise

    0

    Mid-Market

    Assessment: Well-developed marketing technology stack

    Sponsored

    Scripts & Styles

    21 Resources

    20
    Scripts
    1
    Styles
    14
    Async
    1
    Defer

    Top Script Sources

    local(14)beacon-v2.helpscout.net(3)googletagmanager.com(3)

    Website Identity

    CodeCrafters

    CodeCrafters

    Organization

    CodeCrafters is a hands-on learning platform offering advanced, real-world projects that push engineers to master software craftsmanship through building complex systems from scratch.

    sarup@codecrafters.io
    6 years old
    Location detected: 🇺🇸 United Statesvia ip
    Gandi SAS📧 Google WorkspaceenEst. 2022

    Sponsored

    Last analyzed: 25 May 2026 at 02:31

    Historical Analysis & Change Tracking