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https://Metafilter.com

Performance

· 25 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
92
GRADE
A
FIX
2
REVIEW
4
PASS
17
INFO
2

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

Mobile Desktop
67
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.
81
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
100
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.

5.17 s

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

5.17 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.

0.000

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

5.56 s

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

5.17 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
25
17 PASS 4 REVIEW 2 FIX
D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (224.5 KiB of 224.9 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
No Cache-Control header found
Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

B
JS Execution Cost
887ms total JS execution
REVIEW
887ms total JS execution
Warning::
https://www.metafilter.com/: 376ms CPU time
Warning::
https://www.metafilter.com/cdn-cgi/challenge-platf...: 277ms CPU time
Info::
https://dha92jo6cen2v.cloudfront.net/scripts/mefi/...: 119ms CPU time
Info::
Unattributable: 115ms CPU time
Warning::
Third-party scripts: 887ms (100% of total)

Main Thread Breakdown

Style & Layout 38% Script Evaluation 36% Other 16% Parse HTML & CSS 5% Rendering 3%
ScriptTotalScriptingParse/CompileParty
https://www.metafilter.com/376ms29ms4ms3rd
https://www.metafilter.com/cdn-cgi/challenge-platform/scripts/jsd/main.js277ms222ms2ms3rd
https://dha92jo6cen2v.cloudfront.net/scripts/mefi/libscript20250324.2113.js119ms64ms9ms3rd
Unattributable115ms6ms0ms3rd
C
Compression Algorithm
Action
Main response served uncompressed
REVIEW
Main response served uncompressed
Info::
Main HTML response has no Content-Encoding (uncompressed)
The main HTML document is served without compression. The Text Compression section above lists the broader picture; for the main response specifically, even gzip would shave ~70-80% off most text payloads.
B
Main HTML Cache-Control
No Cache-Control header on main HTML response
REVIEW
No Cache-Control header on main HTML response
Info::
Main HTML response has no Cache-Control header
Without an explicit Cache-Control, browsers fall back to heuristic caching (~10% of Last-Modified age). Set `Cache-Control: no-cache` or `max-age=300` for HTML to control freshness explicitly -- prevents stale auth state and SPA shell drift.
B
Server-Timing Observability
No Server-Timing header found
REVIEW
No Server-Timing header found
Info::
No Server-Timing header found
Server-Timing exposes backend timing breakdowns to browser DevTools (e.g., `db: 45ms; render: 120ms; cache: 2ms`). Useful for diagnosing slow pages without backend log access. Most modern frameworks (Next.js, Cloudflare Workers, Fastly) emit it automatically; absence on a managed platform usually means telemetry headers are stripped at the edge.
A+
Page Weight Budget
225 KB transferred, 18 requests
PASS
225 KB transferred, 18 requests
Info::
Page weighs 777 KB (225 KB transferred)
Info::
18 HTTP requests
Info::
Estimated 0.05 g CO2 per page load
225 KB / 2.4 MB budget
225 KB transferred
18 requests
0.05 g CO2 per page load
JavaScript 73.4 KiB 33%
Fonts 72.8 KiB 32%
CSS 45.7 KiB 20%
HTML 21.7 KiB 10%
Other 9.4 KiB 4%
Other 1.9 KiB 1%
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+
Image Optimization
No images on this page
PASS
No images on this page
Info::
No images on this page
0 images 0 KB
0 oversized -0 KB
0 legacy format
0 missing dimensions CLS risk
A+
Font Loading
5 fonts (73 KB)
PASS
5 fonts (73 KB)
Info::
5 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

5

73 KB total

Render-blocking

0

of 5

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s FCP 5.2 s LCP 5.2 shttps://fonts.gstatic.com/s/montserrat/v31/JTUHjIg1_i6t8kCHKm4532VJOt5-QNFgpCtr6Hw5aXp-obK4.woff2JTUHjIg1_i6t8kCHKm4532V... https://fonts.gstatic.com/s/montserrat/v31/JTUHjIg1_i6t8kCHKm4532VJOt5-QNFgpCtr6Hw5aXp-obK4.woff2 — 16.0 KiB — 92 ms — font-display: swaphttps://fonts.gstatic.com/s/sourcesanspro/v23/6xKydSBYKcSV-LCoeQqfX1RYOo3i54rwlxdu3cOWxw.woff26xKydSBYKcSV-LCoeQqfX1R... https://fonts.gstatic.com/s/sourcesanspro/v23/6xKydSBYKcSV-LCoeQqfX1RYOo3i54rwlxdu3cOWxw.woff2 — 14.6 KiB — 62 ms — font-display: swaphttps://fonts.gstatic.com/s/sourcesanspro/v23/6xK3dSBYKcSV-LCoeQqfX1RYOo3qOK7lujVj9w.woff26xK3dSBYKcSV-LCoeQqfX1R... https://fonts.gstatic.com/s/sourcesanspro/v23/6xK3dSBYKcSV-LCoeQqfX1RYOo3qOK7lujVj9w.woff2 — 14.5 KiB — 83 ms — font-display: swaphttps://fonts.gstatic.com/s/sourcesanspro/v23/6xK1dSBYKcSV-LCoeQqfX1RYOo3qPZ7nsDJB9cme.woff26xK1dSBYKcSV-LCoeQqfX1R... https://fonts.gstatic.com/s/sourcesanspro/v23/6xK1dSBYKcSV-LCoeQqfX1RYOo3qPZ7nsDJB9cme.woff2 — 13.9 KiB — 51 ms — font-display: swaphttps://fonts.gstatic.com/s/sourcesanspro/v23/6xKwdSBYKcSV-LCoeQqfX1RYOo3qPZY4lCds18S0xR41.woff26xKwdSBYKcSV-LCoeQqfX1R... https://fonts.gstatic.com/s/sourcesanspro/v23/6xKwdSBYKcSV-LCoeQqfX1RYOo3qPZY4lCds18S0xR41.woff2 — 13.9 KiB — 73 ms — font-display: swap
JTUHjIg1_i6t8kCHKm4532V... woff2 swap
Size 16 KB
Load time 92 ms
Start 679 ms
Risk FOUT — text flashes from fallback to web font
6xKydSBYKcSV-LCoeQqfX1R... woff2 swap
Size 15 KB
Load time 62 ms
Start 679 ms
Risk FOUT — text flashes from fallback to web font
6xK3dSBYKcSV-LCoeQqfX1R... woff2 swap
Size 15 KB
Load time 83 ms
Start 679 ms
Risk FOUT — text flashes from fallback to web font
6xK1dSBYKcSV-LCoeQqfX1R... woff2 swap
Size 14 KB
Load time 51 ms
Start 679 ms
Risk FOUT — text flashes from fallback to web font
6xKwdSBYKcSV-LCoeQqfX1R... woff2 swap
Size 14 KB
Load time 73 ms
Start 680 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+
JS Bundles
4 scripts, 31 KB unused
PASS
4 scripts, 31 KB unused
Warning::
https://dha92jo6cen2v.cloudfront.net/scripts/mefi/...: 31 KB unused (65%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 31 KB
31 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://dha92jo6cen2v.cloudfront.net/scripts/mefi/libscript20250324.2113.js49 KB31 KB (65%)✓3rd
https://dha92jo6cen2v.cloudfront.net/scripts/mefi/pageload092414.mod.js7 KB—✓3rd
https://dha92jo6cen2v.cloudfront.net/scripts/mefi/members20250324.2113.js8 KB—✓3rd
https://www.metafilter.com/cdn-cgi/challenge-platform/h/g/scripts/jsd/fe6331af5207/main.js?10 KB—✓3rd

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

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/3 (QUIC)
HTTP/3 advertised via Alt-Svc
PASS
HTTP/3 advertised via Alt-Svc
Info::
HTTP/3 (QUIC) is supported
First-load mobile users on cellular networks see meaningful latency improvements with HTTP/3. The QUIC transport collapses TLS + TCP handshakes into one and recovers faster from packet loss.
A+
LCP Image Preload
LCP preload audit not available
PASS
LCP preload audit not available
Info::
LCP image preload audit not available for this scan
A+
Server Response Intelligence
1 server-response signal(s) detected
PASS
1 server-response signal(s) detected
Info::
No `ETag` or `Last-Modified` -- conditional GET not supported
Without either header, browsers can't issue conditional GETs and refresh always re-downloads the full response body even when nothing changed. Add `ETag: "<hash>"` (or `Last-Modified: <date>`) on cacheable responses; the server returns 304 Not Modified when the client's cached copy is still valid, saving bandwidth.
A
Page Weight Inventory
18 resources · 225 KB · 31 KB savings available
PASS
18 resources · 225 KB · 31 KB savings available
Info::
Within 1MB page-weight target
Got: 225 KB
Warning::
17 third-party resources (100% of weight)
18 resources · 224.9 KiB · 17 third-party Within 1MB page-weight target
JavaScript 33% · 73.4 KiB
Font 32% · 72.8 KiB
CSS 20% · 45.7 KiB
Document 10% · 21.7 KiB
Image 4% · 10.1 KiB
Other 1% · 1.2 KiB

~31.3 KiB of savings available

Remove unused JavaScript: 31.3 KiB
A+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
No render-blocking resources detected in <head>
A+
Third-Party Resources
No third-party resources detected
PASS
No third-party resources detected
A
JavaScript Blocking
1 JS blocking issue(s) detected
PASS
1 JS blocking issue(s) detected
Warning::
4 render-blocking <script src> tag(s) without async/defer
Each `<script src=...>` without `async`, `defer`, or `type="module"` blocks HTML parsing while the browser fetches and executes it. The block lasts the entire round-trip + execution time -- on slow networks this translates directly into LCP delay. Add `defer` (executes after parse, in source order) for scripts that interact with the DOM, or `async` (executes whenever ready) for analytics / independent scripts. Module scripts (`type="module"`) are deferred by default.
A+
CSS Performance Depth
No CSS performance depth issues detected
PASS
No CSS performance depth issues detected
Info::
No CSS performance depth issues detected
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
18 requests over 854ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s FCP 5.2 s LCP 5.2 shttps://metafilter.com// https://metafilter.com/ — 301 — 400 B — 62 ms — h2https://www.metafilter.com/www.metafilter.com/ https://www.metafilter.com/ — 200 — 21.7 KiB — 267 ms — h2https://dha92jo6cen2v.cloudfront.net/styles/mefi/style20250529.3336.cssdha92jo6cen2v.cloudfront.net/styles... https://dha92jo6cen2v.cloudfront.net/styles/mefi/style20250529.3336.css — 200 — 36.6 KiB — 109 ms — http/1.1https://dha92jo6cen2v.cloudfront.net/styles/mefi/dark-mode20250529.3336.cssdha92jo6cen2v.cloudfront.net/styles... https://dha92jo6cen2v.cloudfront.net/styles/mefi/dark-mode20250529.3336.css — 200 — 7.7 KiB — 108 ms — http/1.1https://dha92jo6cen2v.cloudfront.net/scripts/mefi/pageload092414.mod.jsdha92jo6cen2v.cloudfront.net/script... https://dha92jo6cen2v.cloudfront.net/scripts/mefi/pageload092414.mod.js — 200 — 6.8 KiB — 109 ms — http/1.1https://dha92jo6cen2v.cloudfront.net/scripts/mefi/libscript20250324.2113.jsdha92jo6cen2v.cloudfront.net/script... https://dha92jo6cen2v.cloudfront.net/scripts/mefi/libscript20250324.2113.js — 200 — 48.7 KiB — 121 ms — http/1.1https://dha92jo6cen2v.cloudfront.net/scripts/mefi/members20250324.2113.jsdha92jo6cen2v.cloudfront.net/script... https://dha92jo6cen2v.cloudfront.net/scripts/mefi/members20250324.2113.js — 200 — 7.7 KiB — 110 ms — http/1.1https://fonts.googleapis.com/css2?family=Montserrat&family=Source+Sans+Pro:ital,wght@0,400;0,600;1,400;1,600&display=swapfonts.googleapis.com/css2?family=Mo... https://fonts.googleapis.com/css2?family=Montserrat&family=Source+Sans+Pro:ital,wght@0,400;0,600;1,400;1,600&display=swap — 200 — 1.4 KiB — 149 ms — h2https://dha92jo6cen2v.cloudfront.net/images/icons.svgdha92jo6cen2v.cloudfront.net/images... https://dha92jo6cen2v.cloudfront.net/images/icons.svg — 200 — 8.7 KiB — 57 ms — http/1.1https://fonts.gstatic.com/s/montserrat/v31/JTUHjIg1_i6t8kCHKm4532VJOt5-QNFgpCtr6Hw5aXp-obK4.woff2fonts.gstatic.com/s/montserrat/v31/... https://fonts.gstatic.com/s/montserrat/v31/JTUHjIg1_i6t8kCHKm4532VJOt5-QNFgpCtr6Hw5aXp-obK4.woff2 — 200 — 16.0 KiB — 92 ms — h3https://fonts.gstatic.com/s/sourcesanspro/v23/6xKydSBYKcSV-LCoeQqfX1RYOo3i54rwlxdu3cOWxw.woff2fonts.gstatic.com/s/sourcesanspro/v... https://fonts.gstatic.com/s/sourcesanspro/v23/6xKydSBYKcSV-LCoeQqfX1RYOo3i54rwlxdu3cOWxw.woff2 — 200 — 14.6 KiB — 62 ms — h3https://fonts.gstatic.com/s/sourcesanspro/v23/6xK3dSBYKcSV-LCoeQqfX1RYOo3qOK7lujVj9w.woff2fonts.gstatic.com/s/sourcesanspro/v... https://fonts.gstatic.com/s/sourcesanspro/v23/6xK3dSBYKcSV-LCoeQqfX1RYOo3qOK7lujVj9w.woff2 — 200 — 14.5 KiB — 83 ms — h3https://fonts.gstatic.com/s/sourcesanspro/v23/6xK1dSBYKcSV-LCoeQqfX1RYOo3qPZ7nsDJB9cme.woff2fonts.gstatic.com/s/sourcesanspro/v... https://fonts.gstatic.com/s/sourcesanspro/v23/6xK1dSBYKcSV-LCoeQqfX1RYOo3qPZ7nsDJB9cme.woff2 — 200 — 13.9 KiB — 51 ms — h3https://fonts.gstatic.com/s/sourcesanspro/v23/6xKwdSBYKcSV-LCoeQqfX1RYOo3qPZY4lCds18S0xR41.woff2fonts.gstatic.com/s/sourcesanspro/v... https://fonts.gstatic.com/s/sourcesanspro/v23/6xKwdSBYKcSV-LCoeQqfX1RYOo3qPZY4lCds18S0xR41.woff2 — 200 — 13.9 KiB — 73 ms — h3https://www.metafilter.com/cdn-cgi/challenge-platform/scripts/jsd/main.jswww.metafilter.com/cdn-cgi/challeng... https://www.metafilter.com/cdn-cgi/challenge-platform/scripts/jsd/main.js — 302 — 140 B — 21 ms — h2https://www.metafilter.com/cdn-cgi/challenge-platform/h/g/scripts/jsd/fe6331af5207/main.js?www.metafilter.com/cdn-cgi/challeng... https://www.metafilter.com/cdn-cgi/challenge-platform/h/g/scripts/jsd/fe6331af5207/main.js? — 200 — 10.1 KiB — 24 ms — h2https://www.metafilter.com/cdn-cgi/challenge-platform/h/g/jsd/oneshot/fe6331af5207/0.10954940652842726:1778415760:_V4GtjpQpawIYUFI1am372I1yutyCkcxwjb-SI7jg64/9f993eaa0bebd128www.metafilter.com/cdn-cgi/challeng... https://www.metafilter.com/cdn-cgi/challenge-platform/h/g/jsd/oneshot/fe6331af5207/0.10954940652842726:1778415760:_V4GtjpQpawIYUFI1am372I1yutyCkcxwjb-SI7jg64/9f993eaa0bebd128 — 200 — 667 B — 28 ms — h3https://dha92jo6cen2v.cloudfront.net/styles/mefi/favicon030514b.icodha92jo6cen2v.cloudfront.net/styles... https://dha92jo6cen2v.cloudfront.net/styles/mefi/favicon030514b.ico — 200 — 1.4 KiB — 21 ms — http/1.1
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
100% of JavaScript execution is third-party
First-party Third-party 887ms · 71KB · €10/mo
www.metafilter.com
Other
Costly
Execution 376ms
Transfer 22 KB
Monthly Cost €4/mo
www.metafilter.com
Other
Costly
Execution 277ms
Transfer 0 KB
Monthly Cost €3/mo
dha92jo6cen2v.cloudfront.net
Other
Optional
Execution 119ms
Transfer 49 KB
Unused 65%
Monthly Cost €1/mo
Unattributable
Other
Optional
Execution 115ms
Transfer 0 KB
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • www.metafilter.com adds 376ms and costs ~€4/month
  • www.metafilter.com adds 277ms and costs ~€3/month

100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.

Why this matters

When third-party JS execution time exceeds your own, performance gains from frontend work are capped by code you don't own.

Learn more ▾

Every millisecond of third-party JS competes with your own for main-thread time. If their share is bigger than yours, optimization on your code base barely moves the needle. Audit, defer, or remove third-parties before further frontend optimization. Use Lighthouse's third-party audit to identify the worst offenders.

Source: web.dev

www.metafilter.com takes 376ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

www.metafilter.com takes 277ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

65% of dha92jo6cen2v.cloudfront.net'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.

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