vosviewer.com

https://vosviewer.com· First analyzed 16 May 2026· Updated 16 May 2026

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vosviewer.com

Mobile

Sponsored

Hosting Provider

Universiteit Leiden

IP Address

132.229.26.33

Site Location

🇳🇱 Netherlandsvia ip

Server Location

🇳🇱 Oegstgeest, Netherlands

ASN

AS1103

Organization

Universiteit Leiden

Nameservers

ns2.surfnet.nl.ns1.surfnet.nl.ns3.surfnet.nl.

Performance

Core Web Vitals

Weight

First Contentful Paint

992 ms10%

Speed Index

1.3 s10%

Largest Contentful Paint

—25%

Total Blocking Time

0.0 ms30%

Cumulative Layout Shift

0.00025%

2.9 MB

53 requests

0–49

50–89

90–100

Architecture Stack

Monolithic

⚙️ SSR

Infrastructure

Hosting

Universiteit Leiden

Technology Stack

5 Technologies Detected

Libraries

CSS Frameworks

Analytics

Customer Support

SEO Analysis

B71/100

Meta Tags12/15

Content11/12

Headings8/8

Technical15/25

E-E-A-T0/7

Images1/7

Links5/5

URL5/5

Social5/5

Freshness2/4

Mobile4/4

Indexability3/3

vosviewer.comvosviewer.com

VOSviewer - Visualizing scientific landscapes

VOSviewer is a software tool for constructing and visualizing bibliometric networks.

Title Length45 chars

Recommended: 50-60 chars (~264px / 580px)

Description Length84 chars

Recommended: 120-160 chars

Issues (2)

• Most images missing alt text (11/16) — critical for accessibility and SEO
• Missing viewport meta tag — page may not be mobile-friendly (Google uses mobile-first indexing)

7 issues found

Upgrade to view details

Crawlability

Sitemap

Type: standard

9 URLs

robots.txt

7 rules

Sitemap reference found

Local SEO

Local Search Readiness

11/100

Poor

3 12 2

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

Sponsored

AI & LLM Readiness

D50/100

Bot Access

20/25

Machine Read.

14/25

Schema Data

0/25

Citation

16/25

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

navheader/footer

Text ratio:12%

Words:705

Token eff.:Optimal

Sections/1K:44

Depth:2/5

Structured Data

No Schema

Citation Readiness

Opening Summary24w

Descriptive Headingsavg 6w

Canonical URL

Open Graph3/3

Twitter Card3/3

Language Tag

Publish Date

Author Info

Lists

Tables

TL;DR / Summary

About Page Link

Recommendations (6)

AI readiness recommendation preview...

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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.

76/100

Passed

Critical

Warnings

Images & Alt Text

15/20

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

7/15

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.

2 recommendations

•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.

16/100

368 mg

CO₂e / view

2.9 MB

Page Weight

30%

Cleaner Than

New Visitor

421 mg

Returning (cached)

210 mg

Annual (10K/mo)

44.2 kg

Emission Segments

Data Center

82 mg

Network

88 mg

Device

198 mg

Resource Breakdown

JavaScript

261.2 KB

Images

2.4 MB

CSS

212.2 KB

HTML

12.8 KB

Other

1.7 KB

Green Hosting Not Verified

Universiteit Leiden

6 recommendations

•Carbon footprint recommendation preview...

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Security Score

56%Poor

Interactive

HTTPS

No WAF

178d

Certificate Details

Type

Organization Validated (OV)

Certificate Authority

Hellenic Academic and Research Institutions CA

Key Algorithm

RSA (4096 bit)

Signature

SHA-256 with RSA

TLS Version

TLSv1.2

HTTP Protocol

HTTP/2

Valid From

10.11.2025

Valid Until

10.11.2026

OCSP Stapling

Enabled

Subject Alternative Names (4)

vosviewer.comwww.vosviewer.comweb.vosviewer.comapp.vosviewer.com

SHA-256 Fingerprint

FD:2F:59:1F:FB:0B:B2:09:CB:0E:56:FF:2A:B0:9D:5B:64:EB:81:E0...

Top Recommendations

Security recommendation preview

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HTTP Headers

Developer Console

cache-control

🔴 No Cache(no-store, no-cache, must-revalidate)

content-encoding

📦 Gzip(gzip)

content-length

12756

content-type

text/html; charset=iso-8859-1

date

Sat, 16 May 2026 05:12:49 GMT

expires

Thu, 19 Nov 1981 08:52:00 GMT

Good Warning Issue

Email Infrastructure

Custom Mail Server

Score

SPF

DKIM

DMARC

Domain Information

vosviewer.com

Domain Age

16y 10m

Created

03.07.2009

Expires

03.07.2026

Last Updated

30.11.2025

Registrar

Key-Systems GmbH

DNSSEC

Not Enabled

Privacy & Compliance

Cookie Consent Banner

GDPR Indicators

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.

37/100

Not 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.

3 recommendations

•Mobile compatibility recommendation preview...

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Typography & Readability

Open Sans

WCAG Partial

60/100

Readability

/30

16/30

13px · LH 1.54

Hierarchy

/20

19/20

2.31x ratio · ✓ H1→H6

WCAG

/25

14/25

1.14:1 min contrast

Performance

/25

11/25

1 font · 4 req

Heading Font

Open Sans

Sans30px

Body Font

Open Sans

Sans13px

Contrast Ratio

1.14:1

12 issues

Reading Comfort

~34 CPL

Narrow lines

30px

18px

13px

❌ Critical: 13px body text is too small. Minimum 14px, recommend 16px+.

✅ Optimal line spacing: 1.54 ratio (ideal range 1.4–1.6).

⚠️ Hard to read: Flesch score 40/100. Simplify sentences for wider reach.

⚠️ Partial contrast: 12 elements below WCAG AA threshold (min 1.1:1).

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

✅ Strong hierarchy: Headlines are 2.3x larger than body text.

Buy on MyFontsFlesch 40

Color Palette

8 unique colors

Light

#ffffff

Background· 35%

#1f7896

Primary· 25.299999999999997%

#8da0a9

Secondary· 5.2%

#14576d

Accent· 4.8%

#3f6375

Secondary· 2.1%

Business & Marketing Stack

2 Tools Detected

Growing

Behavior Analytics

PlausibleSMB

Google AnalyticsFree

User behavior and product analytics

Sponsored

Scripts & Styles

10 Resources

Scripts

Styles

Async

Defer

Top Script Sources

local(4)plausible.io(1)

Website Identity

vosviewer.com

16 years old

Location detected: 🇳🇱 Netherlandsvia ip

Key-Systems GmbHen

Social Profiles

Facebook X (Twitter)

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Last analyzed: 16 May 2026 at 05:13

Historical Analysis & Change Tracking