Skip to content
https://spring.io

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
85
GRADE
B
FIX
0
REVIEW
5
PASS
7
INFO
2

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

Mobile Desktop
97
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
89
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
96
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
92
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.

590 ms

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

1.22 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.

0.008

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

858 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.

1.23 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
7 PASS 5 REVIEW
B
Third-Party Impact
55% third-party, 0 ms blocking
REVIEW
55% third-party, 0 ms blocking
Warning::
Third-party code accounts for 55% of page weight (384.4 KiB of 693.9 KiB)
Info::
Third-party blocking time is low (0 ms)
45%
55%
First-party Third-party
C
Image Optimization
Action
14 images, 0 KB saveable
REVIEW
14 images, 0 KB saveable
Warning::
https://spring.io/img/extra/quote.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://spring.io/img/extra/footer.svg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
14 images 79 KB
0 oversized -0 KB
14 legacy format
2 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

B
JS Execution Cost
681ms total JS execution
REVIEW
681ms total JS execution
Info::
https://spring.io/: 229ms CPU time
Info::
https://spring.io/framework-f0de980621661f0b7a47.j...: 154ms CPU time
Info::
Unattributable: 139ms CPU time
Info::
https://cdn.cookielaw.org/scripttemplates/202509.1...: 103ms CPU time
Info::
https://www.googletagmanager.com/gtm.js?id=GTM-W8C...: 56ms CPU time
Info::
Third-party scripts: 298ms (44% of total)

Main Thread Breakdown

Script Evaluation 36% Other 28% Style & Layout 19% Script Parsing & Compilation 7% Parse HTML & CSS 5% Rendering 4%
ScriptTotalScriptingParse/CompileParty
https://spring.io/229ms14ms2ms1st
https://spring.io/framework-f0de980621661f0b7a47.js154ms97ms5ms1st
Unattributable139ms21ms0ms3rd
https://cdn.cookielaw.org/scripttemplates/202509.1.0/otBannerSdk.js103ms65ms19ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-W8CQ8TL56ms42ms13ms3rd
B
JS Bundles
13 scripts, 138 KB unused
REVIEW
13 scripts, 138 KB unused
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-W8C...: 74 KB unused (56%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cdn.cookielaw.org/scripttemplates/202509.1...: 64 KB unused (53%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 138 KB
138 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtm.js?id=GTM-W8CQ8TL133 KB74 KB (56%)✓3rd
https://cdn.cookielaw.org/scripttemplates/202509.1.0/otBannerSdk.js122 KB64 KB (53%)✓3rd
https://spring.io/app-eb2299719d986c7bfa17.js24 KB—✓1st
https://cdn.cookielaw.org/scripttemplates/otSDKStub.js9 KB—✓3rd
https://static.cloudflareinsights.com/beacon.min.js11 KB—✓3rd
https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da177152312451611 KB—✓3rd
https://spring.io/framework-f0de980621661f0b7a47.js45 KB—✓1st
https://spring.io/c16184b3-bf3bd3a4ce2c0f7585be.js3 KB—✓1st
https://spring.io/2cca2479-52cc2fee7444ce8367e9.js2 KB—✓1st
https://spring.io/commons-522737e33bff6863b536.js34 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

B
HTTP Caching
public, max-age=0, must-revalidate
REVIEW
public, max-age=0, must-revalidate
Info::
Cache-Control header is set
Got: public, max-age=0, must-revalidate
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

public, max-age=0, must-revalidate

DirectiveValueMeaning
public—Any cache may store this response
max-age0Cache for 0 seconds
must-revalidate—Must recheck with server after expiry
A+
Page Weight Budget
694 KB transferred, 51 requests
PASS
694 KB transferred, 51 requests
Info::
Page weighs 2.1 MB (694 KB transferred)
Info::
51 HTTP requests
Info::
Estimated 0.14 g CO2 per page load
694 KB / 2.4 MB budget
694 KB transferred
51 requests
0.14 g CO2 per page load
JavaScript 402.2 KiB 58%
Fonts 95.8 KiB 14%
Images 79.2 KiB 11%
HTML 63.3 KiB 9%
Other 37.8 KiB 5%
Other 8.3 KiB 1%
Other 6.4 KiB 1%
Other 789 B 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Under budget
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+
Font Loading
6 fonts (96 KB)
PASS
6 fonts (96 KB)
Info::
6 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

6

96 KB total

Render-blocking

0

of 6

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s FCP 590 ms LCP 1.2 shttps://spring.io/fonts/open-sans-v17-latin/open-sans-v17-latin-regular.woff2open-sans-v17-latin-reg... https://spring.io/fonts/open-sans-v17-latin/open-sans-v17-latin-regular.woff2 — 14.3 KiB — 0 ms — font-display: swaphttps://spring.io/fonts/metropolis/metropolis-bold-webfont.woff2metropolis-bold-webfont... https://spring.io/fonts/metropolis/metropolis-bold-webfont.woff2 — 14.8 KiB — 0 ms — font-display: swaphttps://spring.io/fonts/open-sans-v17-latin/open-sans-v17-latin-700.woff2open-sans-v17-latin-700... https://spring.io/fonts/open-sans-v17-latin/open-sans-v17-latin-700.woff2 — 15.0 KiB — 0 ms — font-display: swaphttps://spring.io/fonts/metropolis/metropolis-extrabold-webfont.woff2metropolis-extrabold-we... https://spring.io/fonts/metropolis/metropolis-extrabold-webfont.woff2 — 14.7 KiB — 0 ms — font-display: swaphttps://spring.io/fonts/work-sans-v5-latin/work-sans-v5-latin-regular.woff2work-sans-v5-latin-regu... https://spring.io/fonts/work-sans-v5-latin/work-sans-v5-latin-regular.woff2 — 22.2 KiB — 0 ms — font-display: swaphttps://spring.io/fonts/open-sans-v17-latin/open-sans-v17-latin-600.woff2open-sans-v17-latin-600... https://spring.io/fonts/open-sans-v17-latin/open-sans-v17-latin-600.woff2 — 14.8 KiB — 0 ms — font-display: swap
open-sans-v17-latin-reg... woff2 swap
Size 14 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
metropolis-bold-webfont... woff2 swap
Size 15 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
open-sans-v17-latin-700... woff2 swap
Size 15 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
metropolis-extrabold-we... woff2 swap
Size 15 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
work-sans-v5-latin-regu... woff2 swap
Size 22 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
open-sans-v17-latin-600... woff2 swap
Size 15 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+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

Network Waterfall
51 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
44% of JavaScript execution is third-party
First-party Third-party 298ms · 254KB · $1/mo
Unattributable
Other
Optional
Execution 139ms
Transfer 0 KB
Monthly Cost $0/mo
OneTrust
Consent
Essential
Execution 103ms
Transfer 122 KB
Unused 53%
Monthly Cost $0/mo
Google Tag Manager
Tag Manager
Optional
Execution 56ms
Transfer 133 KB
Unused 56%
Monthly Cost $0/mo

44% 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

53% of OneTrust's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

56% of Google Tag Manager's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

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.

Send Feedback