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containers.dev

https://containers.dev· First analyzed 15 May 2026· Updated 15 May 2026
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containers.dev
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Hosting Provider

GitHub Pages
pages.github.com

IP Address

185.199.109.153

Site Location

🇺🇸 United Statesvia ip

Server Location

🇺🇸 San Francisco, United States

ASN

AS54113

Organization

GitHub, Inc

Server

GitHub.com

CDN

Fastly

Nameservers

ns1-34.azure-dns.com.ns2-34.azure-dns.net.ns3-34.azure-dns.org.ns4-34.azure-dns.info.

Performance

100

Core Web Vitals

Weight

First Contentful Paint
586 ms10%
Speed Index
762 ms10%
Largest Contentful Paint
—25%
Total Blocking Time
0.0 ms30%
Cumulative Layout Shift
0.00025%
205 KB
20 requests
0–49
50–89
90–100

Architecture Stack

Monolithic
⚙️ SSR
Frontend
Styling
Bootstrap
Infrastructure
Platform
GitHub Pages
CDN
Fastly

Technology Stack

5 Technologies Detected

CSS Frameworks

2
Bootstrapv4.0.0
Tailwind CSS

Libraries

1
jQueryv3.2.1

Icon Libraries

1
Font Awesome

Analytics

1
Google Analytics

SEO Analysis

D54/100
16
7
0
Meta Tags5/15
Content9/12
Headings6/8
Technical14/21
E-E-A-T0/7
Images4/7
Links4/5
URL5/5
Social0/5
Freshness0/4
Mobile4/4
Indexability3/3
C
containers.devcontainers.dev

Development containers

Development containers documentation and specification page.

Title Length22 chars

Recommended: 50-60 chars (~134px / 580px)

Description Length61 chars

Recommended: 120-160 chars

Issues (0)

    7 issues found

    Upgrade to view details

    Local SEO

    Local Search Readiness

    3/100
    Poor
    1 14 2

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

    Sponsored

    AI & LLM Readiness

    F36/100
    Bot Access
    20/25
    Machine Read.
    6/25
    Schema Data
    0/25
    Citation
    10/25

    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
    header/footer
    Text ratio:17%
    Words:216
    Token eff.:Too Short
    Sections/1K:18.5
    Depth:1/5

    Structured Data

    No Schema

    Citation Readiness

    Opening Summary12w
    Descriptive Headingsavg 2w
    Canonical URL
    Open Graph0/3
    Twitter Card0/3
    Language Tag
    Publish Date
    Author Info
    Lists
    Tables
    TL;DR / Summary
    About Page Link
    Recommendations (10)
    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
    81/100
    11
    Passed
    3
    Critical
    0
    Warnings
    Images & Alt Text
    20/20
    Checks if images have descriptive alt text for screen readers and visually impaired users.
    Semantic Structure
    16/20
    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
    9/15
    Ensures all interactive elements are reachable and operable via keyboard (tab, enter, escape).
    ARIA & Roles
    6/15
    Checks correct use of WAI-ARIA attributes (roles, states, properties) for assistive technologies.
    1 recommendation
    • •Accessibility recommendation preview...
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    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.
    55/100
    A+
    25 mg
    CO₂e / view
    204.7 KB
    Page Weight
    95%
    Cleaner Than
    New Visitor
    29 mg
    vs
    Returning (cached)
    15 mg
    Annual (10K/mo)
    3.0 kg
    Emission Segments
    Data Center
    6 mg
    Network
    6 mg
    Device
    14 mg
    Resource Breakdown
    JavaScript
    1.8 KB
    Images
    169.7 KB
    CSS
    29.9 KB
    HTML
    3.2 KB
    Green Hosting Not Verified
    GitHub Pages
    4 recommendations
    • •Carbon footprint recommendation preview...
    Upgrade to view recommendations
    B

    Security Score

    71%Good
    Static / Informational

    HTTPS

    No WAF

    65d

    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

    21.04.2026

    Valid Until

    20.07.2026

    Subject Alternative Names (2)

    containers.devwww.containers.dev

    SHA-256 Fingerprint

    0D:4C:F5:6F:A3:41:F8:F6:1F:87:45:F4:E7:F6:10:F8:53:E3:3A:34...

    Recommendations

    Security recommendation preview

    Upgrade to view recommendations
    Upgrade to view header details

    HTTP Headers

    Developer Console

    accept-ranges
    bytes
    access-control-allow-origin
    *
    age
    0
    cache-control
    🟡 600s(max-age=600)
    content-encoding
    📦 Gzip(gzip)
    content-length
    3024
    Good Warning Issue

    Email Infrastructure

    Custom Mail Server

    Score

    25

    SPF
    DKIM
    DMARC

    DMARC Policy

    Reject (Strictest)

    Domain Information

    containers.dev

    DNSSEC
    Not Enabled

    Privacy & Compliance

    Cookie Consent Banner
    Privacy Policy
    Terms of Service

    GDPR Indicators

    Cookie consent banner detected

    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
    65/100
    Mobile Friendly1 breakpoint
    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

    Segoe UI

    WCAG AA
    79/100
    Readability
    /30
    21/30

    15px · LH 1.50

    Hierarchy
    /20
    17/20

    2.5x ratio

    WCAG
    /25
    22/25

    6.12:1 min contrast

    Performance
    /25
    19/25

    System fonts

    Heading Font

    Segoe UI

    Sans38px

    Body Font

    Segoe UI

    Sans15px

    Contrast Ratio

    6.12:1

    WCAG AA (≥4.5:1)

    Reading Comfort

    ~43 CPL

    Narrow lines
    38px
    h1
    30px
    h2
    26px
    h3
    15px
    p

    ⚠️ Small text: 15px may strain on mobile. Use ≥16px for WCAG compliance.

    ✅ Optimal line spacing: 1.50 ratio (ideal range 1.4–1.6).

    ❌ Very complex text: Flesch score 24/100. Consider shorter sentences and simpler words.

    ✅ WCAG AA contrast: All text meets 4.5:1 ratio (min 6.1:1).

    ⚠️ Minor heading issue: 0 level skip(s) detected. Maintain sequential order for screen readers.

    ✅ Strong hierarchy: Headlines are 2.5x larger than body text.

    Flesch 24

    Color Palette

    6 unique colors
    Light
    #ffffff
    Background· 45%
    #2653e2
    Primary· 43.400000000000006%
    #aab1c1
    Secondary· 4.7%
    #496bd2
    Accent· 1.5%

    Business & Marketing Stack

    1 Tools Detected

    Growing

    Behavior Analytics

    1
    Google AnalyticsFree

    User behavior and product analytics

    1

    Categories

    1

    Total Tools

    0

    Enterprise

    0

    Mid-Market

    Assessment: Growing marketing technology adoption

    Sponsored

    Scripts & Styles

    12 Resources

    9
    Scripts
    3
    Styles
    3
    Async
    2
    Defer

    Top Script Sources

    buttons.github.io(2)local(2)code.jquery.com(1)wcpstatic.microsoft.com(1)googletagmanager.com(1)

    Website Identity

    containers.dev

    Location detected: 🇺🇸 United Statesvia ip
    en

    Sponsored

    Last analyzed: 15 May 2026 at 01:02

    Historical Analysis & Change Tracking