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https://www.jenkins.io

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
85
GRADE
B
FIX
1
REVIEW
3
PASS
8
INFO
2

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop
91
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
71
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
83
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

607 ms

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

1.88 s

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

0 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.069

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

607 ms

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

1.88 s

Page Load Progression

375 ms
750 ms
1.1 s
1.5 s
1.9 s
2.2 s
2.6 s
3.0 s
Checks
14
8 PASS 3 REVIEW 1 FIX
F
Page Weight Budget
Action
5.3 MB transferred, 74 requests
FIX
5.3 MB transferred, 74 requests
Critical::
Page weighs 8.5 MB (5.3 MB transferred)
Warning::
Images are 4.1 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 4.1 MB
Warning::
JavaScript is 937 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 937 KB
Info::
74 HTTP requests
Info::
Estimated 1.1 g CO2 per page load
5.3 MB / 2.4 MB budget
5.3 MB transferred
74 requests
1.1 g CO2 per page load
Images 4.1 MiB 77%
JavaScript 937.3 KiB 17%
CSS 175.2 KiB 3%
HTML 80.4 KiB 1%
Fonts 33.9 KiB 1%
Other 9.2 KiB 0%
Other 7.1 KiB 0%
Other 732 B 0%
Other 458 B 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Over budget

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Why this matters

Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.

Source: web.dev

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Why this matters

JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.

Source: web.dev

C
Image Optimization
Action
27 images, 0 KB saveable
REVIEW
27 images, 0 KB saveable
Warning::
https://www.jenkins.io/images/post-images/2025/07/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.jenkins.io/images/avatars/stefan_spiek... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.jenkins.io/images/logos/jenkins/jenkin... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.jenkins.io/images/avatars/janfaracik.j... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.jenkins.io/images/avatars/krisstern.pn... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.jenkins.io/images/avatars/timja.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
27 images 4.1 MB
0 oversized -0 KB
25 legacy format
6 missing dimensions CLS risk

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

B
JS Bundles
18 scripts, 55 KB unused
REVIEW
18 scripts, 55 KB unused
Warning::
https://cdn.jsdelivr.net/npm/@docsearch/js@3: 30 KB unused (83%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.jenkins.io/assets/bower/jquery/jquery....: 26 KB unused (73%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 55 KB
55 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://cdn.jsdelivr.net/npm/@docsearch/js@336 KB30 KB (83%)✓3rd
https://www.jenkins.io/assets/bower/jquery/jquery.min.js35 KB26 KB (73%)✓1st
https://cdn.jsdelivr.net/npm/@jenkinsci/jenkins-io-components/+esm26 KB—✓3rd
https://cdnjs.cloudflare.com/ajax/libs/ionicons/7.4.0/ionicons/p-e298ede3.js5 KB—✓3rd
https://www.jenkins.io/assets/bower/bootstrap/js/bootstrap.min.js20 KB—✓1st
https://cdn.jsdelivr.net/npm/lit@3.2.1/polyfill-support.js2 KB—✓3rd
https://cdn.jsdelivr.net/npm/@webcomponents/webcomponentsjs@2.8.0/webcomponents-loader.js3 KB—✓3rd
https://cdnjs.cloudflare.com/ajax/libs/ionicons/7.4.0/ionicons/ionicons.esm.js1 KB—✓3rd
https://www.jenkins.io/assets/bower/anchor-js/anchor.min.js3 KB—✓1st
https://www.jenkins.io/assets/bower/@popperjs/core/umd/popper.min.js8 KB—✓1st

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A
Third-Party Impact
21% third-party, 0 ms blocking
PASS
21% third-party, 0 ms blocking
Info::
Third-party code accounts for 21% of page weight (1.1 MiB of 5.3 MiB)
Info::
Third-party blocking time is low (0 ms)
79%
21%
First-party Third-party
A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
JS Execution Cost
307ms total JS execution
PASS
307ms total JS execution
Info::
https://www.jenkins.io/: 183ms CPU time
Info::
Unattributable: 124ms CPU time
Info::
Third-party scripts: 124ms (41% of total)

Main Thread Breakdown

Other 40% Style & Layout 23% Script Evaluation 22% Rendering 7% Parse HTML & CSS 6%
ScriptTotalScriptingParse/CompileParty
https://www.jenkins.io/183ms8ms0ms1st
Unattributable124ms14ms0ms3rd
A+
Font Loading
1 fonts (34 KB)
PASS
1 fonts (34 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

34 KB total

Render-blocking

0

of 1

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s 1.5 s FCP 607 ms LCP 1.9 shttps://fonts.gstatic.com/s/roboto/v48/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2KFO7CnqEu92Fr1ME7kSn66a... https://fonts.gstatic.com/s/roboto/v48/KFO7CnqEu92Fr1ME7kSn66aGLdTylUAMa3yUBHMdazQ.woff2 — 33.9 KiB — 0 ms — font-display: swap
KFO7CnqEu92Fr1ME7kSn66a... woff2 swap
Size 34 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Optimization checklist
  • Preload critical fonts (priority=high)
  • Use woff2 format for all fonts
  • Set font-display to swap, optional, or fallback
  • Subset large fonts (≤100 KB each)
A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
A+
HTTP Caching
max-age=3600 (1 hour)
PASS
max-age=3600 (1 hour)
Info::
Cache-Control header is set
Got: max-age=3600, public
Info::
Effective TTL: 1 hour (max-age=3600)
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present
Cache-Control

max-age=3600, public

DirectiveValueMeaning
max-age3600Cache for 1 hour
public—Any cache may store this response
Effective TTL: 3600 seconds
Network Waterfall
74 requests over 0ms
INFO

Performance analysis not available for this result.

Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
41% of JavaScript execution is third-party
First-party Third-party 124ms · 0KB · €1/mo
Unattributable
Other
Optional
Execution 124ms
Transfer 0 KB
Monthly Cost €1/mo

41% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

Learn more ▾

Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

How third-party costs are calculated

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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