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https://oxfordlearnersdictionaries.com

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
77
GRADE
C
FIX
4
REVIEW
4
PASS
7
INFO
2

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

Mobile Desktop
57
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
84
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
77
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
85
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.

4.83 s

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

6.38 s

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

334 ms

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

0.002

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

5.16 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.

10.36 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
17
7 PASS 4 REVIEW 4 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 (1.7 MiB of 1.7 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Bundles
Action
15 scripts, 450 KB unused
FIX
15 scripts, 450 KB unused
Warning::
https://securepubads.g.doubleclick.net/pagead/mana...: 143 KB unused (76%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cdn.polarbyte.com/idm/old/pb.min.js: 109 KB unused (80%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.oxfordlearnersdictionaries.com/common....: 86 KB unused (77%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cdn.polarbyte.com/idm/old/iaw.min.js: 43 KB unused (51%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://pagead2.googlesyndication.com/pagead/js/ad...: 35 KB unused (64%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 450 KB
450 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604200101/pubads_impl.js?cb=31098007188 KB143 KB (76%)✓3rd
https://cdn.polarbyte.com/idm/old/pb.min.js137 KB109 KB (80%)✓3rd
https://www.oxfordlearnersdictionaries.com/common.js?version=2.3.76112 KB86 KB (77%)✓3rd
https://cdn.polarbyte.com/idm/old/iaw.min.js85 KB43 KB (51%)✓3rd
https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js54 KB35 KB (64%)✓3rd
https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js0 KB35 KB (64%)✓3rd
data:text/javascript,10 KB—✓3rd
https://www.oxfordlearnersdictionaries.com/external/scripts/doubleclick.js?version=2.3.765 KB—✓3rd
https://www.google-analytics.com/analytics.js21 KB—✓3rd
https://securepubads.g.doubleclick.net/tag/js/gpt.js34 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

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

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

F
Page Weight Inventory
Action
63 resources · 1.7 MB · 450 KB savings available
FIX
63 resources · 1.7 MB · 450 KB savings available
Warning::
Page weight 683 KB over 1MB target
Got: 1.7 MB Expected: ≤ 1 MB
Info::
~450 KB of savings available
Warning::
62 third-party resources (100% of weight)
63 resources · 1.7 MiB · 62 third-party 682.5 KiB over 1MB target
Image 44% · 745.7 KiB
JavaScript 42% · 710.0 KiB
CSS 10% · 166.3 KiB
Font 3% · 43.8 KiB
Other 1% · 24.3 KiB
Document 1% · 16.5 KiB

~450.0 KiB of savings available

Remove unused JavaScript: 450.0 KiB
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.

C
Page Weight Budget
Action
1.7 MB transferred, 63 requests
REVIEW
1.7 MB transferred, 63 requests
Info::
Page weighs 3.5 MB (1.7 MB transferred)
Warning::
JavaScript is 624 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 624 KB
Info::
63 HTTP requests
Info::
Estimated 0.35 g CO2 per page load
1.7 MB / 2.4 MB budget
1.7 MB transferred
63 requests
0.35 g CO2 per page load
Images 729.9 KiB 43%
JavaScript 624.1 KiB 37%
CSS 166.3 KiB 10%
Other 85.9 KiB 5%
Fonts 43.8 KiB 3%
Other 39.0 KiB 2%
HTML 16.3 KiB 1%
Other 1.3 KiB 0%
0 2.4 MB 4.9 MB
Approaching limit

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
28 images, 0 KB saveable
REVIEW
28 images, 0 KB saveable
Warning::
https://dtcfza6z1c8xn.cloudfront.net/grammar-promo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dtcfza6z1c8xn.cloudfront.net/2026_02_otelc... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dtcfza6z1c8xn.cloudfront.net/OLD_WoTM_cult... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dtcfza6z1c8xn.cloudfront.net/OLD_home_Word... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://dtcfza6z1c8xn.cloudfront.net/OLD_home_newt... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.oxfordlearnersdictionaries.com/externa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
28 images 730 KB
0 oversized -0 KB
27 legacy format
15 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

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

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

C
JS Execution Cost
Action
1845ms total JS execution
REVIEW
1845ms total JS execution
Warning::
Unattributable: 449ms CPU time
Warning::
https://www.oxfordlearnersdictionaries.com/common....: 333ms CPU time
Warning::
https://www.oxfordlearnersdictionaries.com/: 276ms CPU time
Info::
https://cdn.polarbyte.com/idm/old/pb.min.js: 206ms CPU time
Info::
https://securepubads.g.doubleclick.net/pagead/mana...: 182ms CPU time
Warning::
Third-party scripts: 1845ms (100% of total)

Main Thread Breakdown

Script Evaluation 50% Other 23% Style & Layout 12% Script Parsing & Compilation 10% Rendering 3%
ScriptTotalScriptingParse/CompileParty
Unattributable449ms85ms0ms3rd
https://www.oxfordlearnersdictionaries.com/common.js?version=2.3.76333ms113ms35ms3rd
https://www.oxfordlearnersdictionaries.com/276ms112ms6ms3rd
https://cdn.polarbyte.com/idm/old/pb.min.js206ms166ms37ms3rd
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202604200101/pubads_impl.js?cb=31098007182ms128ms47ms3rd
https://cdn.polarbyte.com/idm/old/iaw.min.js138ms96ms33ms3rd
https://html-load.com/sdk.js112ms95ms13ms3rd
https://securepubads.g.doubleclick.net/tag/js/gpt.js82ms72ms9ms3rd
https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js68ms52ms16ms3rd
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

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
5 fonts (44 KB)
PASS
5 fonts (44 KB)
Info::
5 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

5

44 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 6.0 s FCP 4.8 s LCP 6.4 shttps://fonts.gstatic.com/s/sourcesanspro/v23/6xK3dSBYKcSV-LCoeQqfX1RYOo3qOK7lujVj9w.woff26xK3dSBYKcSV-LCoeQqfX1R... https://fonts.gstatic.com/s/sourcesanspro/v23/6xK3dSBYKcSV-LCoeQqfX1RYOo3qOK7lujVj9w.woff2 — 14.5 KiB — 63 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 — 40 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 — 53 ms — font-display: swaphttps://www.oxfordlearnersdictionaries.com/external/fonts/oup-icons.ttfoup-icons.ttf https://www.oxfordlearnersdictionaries.com/external/fonts/oup-icons.ttf — 423 B — 174 ms — font-display: swaphttps://www.oxfordlearnersdictionaries.com/external/fonts/oup-icons.woffoup-icons.woff https://www.oxfordlearnersdictionaries.com/external/fonts/oup-icons.woff — 419 B — 106 ms — font-display: swap
6xK3dSBYKcSV-LCoeQqfX1R... woff2 swap
Size 15 KB
Load time 63 ms
Start 1.1 s
Risk FOUT — text flashes from fallback to web font
6xKydSBYKcSV-LCoeQqfX1R... woff2 swap
Size 15 KB
Load time 40 ms
Start 1.1 s
Risk FOUT — text flashes from fallback to web font
6xK1dSBYKcSV-LCoeQqfX1R... woff2 swap
Size 14 KB
Load time 53 ms
Start 1.1 s
Risk FOUT — text flashes from fallback to web font
oup-icons.ttf ttf swap
Size 0 KB
Load time 174 ms
Start 1.1 s
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
oup-icons.woff woff swap
Size 0 KB
Load time 106 ms
Start 1.2 s
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
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
11 hints, 0 missing preconnects
PASS
11 hints, 0 missing preconnects
Info::
Page uses 11 resource hint(s)

Current Resource Hints

preconnect
10
preload
1
dns-prefetch
—
prefetch
—

11 resource hints configured

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
Network Waterfall
63 requests over 1492ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s 6.0 s FCP 4.8 s LCP 6.4 shttps://oxfordlearnersdictionaries.com// https://oxfordlearnersdictionaries.com/ — 301 — 211 B — 114 ms — http/1.1https://www.oxfordlearnersdictionaries.com/www.oxfordlearnersdictionaries.com/ https://www.oxfordlearnersdictionaries.com/ — 200 — 16.3 KiB — 423 ms — h2https://cdn.cookielaw.org/consent/tcf.stub.jscdn.cookielaw.org/consent/tcf.stub.... https://cdn.cookielaw.org/consent/tcf.stub.js — -1 — 0 B — 99 ms — https://cdn.cookielaw.org/scripttemplates/otSDKStub.jscdn.cookielaw.org/scripttemplates/o... https://cdn.cookielaw.org/scripttemplates/otSDKStub.js — -1 — 0 B — 101 ms — https://cdn.polarbyte.com/idm/old/iaw.min.csscdn.polarbyte.com/idm/old/iaw.min.c... https://cdn.polarbyte.com/idm/old/iaw.min.css — 200 — 1.4 KiB — 92 ms — h3https://cdn.polarbyte.com/idm/old/adserver.min.csscdn.polarbyte.com/idm/old/adserver.... https://cdn.polarbyte.com/idm/old/adserver.min.css — 200 — 494 B — 87 ms — h3https://www.google-analytics.com/analytics.jswww.google-analytics.com/analytics.... https://www.google-analytics.com/analytics.js — 200 — 20.9 KiB — 115 ms — h2https://www.oxfordlearnersdictionaries.com/external/styles/interface.css?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/styles/interface.css?version=2.3.76 — 200 — 105.4 KiB — 312 ms — h2https://www.oxfordlearnersdictionaries.com/external/styles/autocomplete.css?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/styles/autocomplete.css?version=2.3.76 — 200 — 3.4 KiB — 311 ms — h2https://www.oxfordlearnersdictionaries.com/external/styles/grid.css?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/styles/grid.css?version=2.3.76 — 200 — 1.5 KiB — 311 ms — h2https://www.oxfordlearnersdictionaries.com/external/styles/footer.css?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/styles/footer.css?version=2.3.76 — 200 — 4.3 KiB — 311 ms — h2https://www.oxfordlearnersdictionaries.com/external/styles/header.css?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/styles/header.css?version=2.3.76 — 200 — 20.0 KiB — 310 ms — h2https://www.oxfordlearnersdictionaries.com/external/styles/responsive.css?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/styles/responsive.css?version=2.3.76 — 200 — 27.2 KiB — 310 ms — h2https://www.oxfordlearnersdictionaries.com/external/images/OLD_logo.svg?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/images/OLD_logo.svg?version=2.3.76 — 200 — 10.0 KiB — 310 ms — h2https://dtcfza6z1c8xn.cloudfront.net/2026_02_otelc-research-image.pngdtcfza6z1c8xn.cloudfront.net/2026_0... https://dtcfza6z1c8xn.cloudfront.net/2026_02_otelc-research-image.png — 200 — 26.5 KiB — 125 ms — h2data:text/javascript,1data:text/javascript,1 data:text/javascript,1 — 200 — 0 B — 0 ms — datahttps://dtcfza6z1c8xn.cloudfront.net/OLD_home_Word_lists_panel5.pngdtcfza6z1c8xn.cloudfront.net/OLD_ho... https://dtcfza6z1c8xn.cloudfront.net/OLD_home_Word_lists_panel5.png — 200 — 20.1 KiB — 22 ms — h2https://dtcfza6z1c8xn.cloudfront.net/OLD_WoTM_culture_war.pngdtcfza6z1c8xn.cloudfront.net/OLD_Wo... https://dtcfza6z1c8xn.cloudfront.net/OLD_WoTM_culture_war.png — 200 — 122.2 KiB — 41 ms — h2https://dtcfza6z1c8xn.cloudfront.net/OLD_home_newtopicsfeature.pngdtcfza6z1c8xn.cloudfront.net/OLD_ho... https://dtcfza6z1c8xn.cloudfront.net/OLD_home_newtopicsfeature.png — 200 — 66.2 KiB — 30 ms — h2https://www.oxfordlearnersdictionaries.com/common.js?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/common.js?version=2.3.76 — 200 — 112.1 KiB — 188 ms — h2https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,400i,600,600i&display=swapfonts.googleapis.com/css?family=Sou... https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,400i,600,600i&display=swap — 200 — 1.3 KiB — 117 ms — h2https://www.oxfordlearnersdictionaries.com/external/scripts/doubleclick.js?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/scripts/doubleclick.js?version=2.3.76 — 200 — 4.8 KiB — 105 ms — h2https://cdn.polarbyte.com/idm/old/pb.min.jscdn.polarbyte.com/idm/old/pb.min.js https://cdn.polarbyte.com/idm/old/pb.min.js — 200 — 136.9 KiB — 79 ms — h3https://securepubads.g.doubleclick.net/tag/js/gpt.jssecurepubads.g.doubleclick.net/tag/... https://securepubads.g.doubleclick.net/tag/js/gpt.js — 200 — 34.1 KiB — 58 ms — h3https://html-load.com/sdk.jshtml-load.com/sdk.js https://html-load.com/sdk.js — 200 — 42.2 KiB — 155 ms — h2https://cdn.polarbyte.com/idm/old/iaw.min.jscdn.polarbyte.com/idm/old/iaw.min.j... https://cdn.polarbyte.com/idm/old/iaw.min.js — 200 — 85.2 KiB — 80 ms — h3https://dtcfza6z1c8xn.cloudfront.net/grammar-promo-square.pngdtcfza6z1c8xn.cloudfront.net/gramma... https://dtcfza6z1c8xn.cloudfront.net/grammar-promo-square.png — 200 — 103.6 KiB — 32 ms — h2https://www.oxfordlearnersdictionaries.com/external/images/home_2020/OLD_home_productsOALD.png?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/images/home_2020/OLD_home_productsOALD.png?version=2.3.76 — 200 — 17.9 KiB — 121 ms — h2https://www.oxfordlearnersdictionaries.com/external/images/home_2020/OLD_home_productsOLDAE.png?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/images/home_2020/OLD_home_productsOLDAE.png?version=2.3.76 — 200 — 78.1 KiB — 133 ms — h2https://www.oxfordlearnersdictionaries.com/external/images/home_2020/OLD_home_productsPEU.png?version=2.3.76www.oxfordlearnersdictionaries.com/... https://www.oxfordlearnersdictionaries.com/external/images/home_2020/OLD_home_productsPEU.png?version=2.3.76 — 200 — 29.1 KiB — 133 ms — h2
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s 6.0 s FCP 4.8 s LCP 6.4 shttps://oxfordlearnersdictionaries.com// https://oxfordlearnersdictionaries.com/ — 301 — 211 B — 114 ms — http/1.1https://www.oxfordlearnersdictionaries.com/www.oxfordlearnersdictionaries.com/ https://www.oxfordlearnersdictionaries.com/ — 200 — 16.3 KiB — 423 ms — h2https://cdn.cookielaw.org/consent/tcf.stub.jscdn.cookielaw.org/consent/tcf.stub.... https://cdn.cookielaw.org/consent/tcf.stub.js — -1 — 0 B — 99 ms — https://cdn.cookielaw.org/scripttemplates/otSDKStub.jscdn.cookielaw.org/scripttemplates/o... https://cdn.cookielaw.org/scripttemplates/otSDKStub.js — -1 — 0 B — 101 ms — https://cdn.polarbyte.com/idm/old/iaw.min.csscdn.polarbyte.com/idm/old/iaw.min.c... https://cdn.polarbyte.com/idm/old/iaw.min.css — 200 — 1.4 KiB — 92 ms — h3https://cdn.polarbyte.com/idm/old/adserver.min.csscdn.polarbyte.com/idm/old/adserver.... https://cdn.polarbyte.com/idm/old/adserver.min.css — 200 — 494 B — 87 ms — 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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 1845ms · 614KB · £19/mo
Unattributable
Other
Costly
Execution 449ms
Transfer 0 KB
Monthly Cost £5/mo
www.oxfordlearnersdictionaries.com
Other
Costly
Execution 333ms
Transfer 112 KB
Unused 77%
Monthly Cost £3/mo
www.oxfordlearnersdictionaries.com
Other
Costly
Execution 276ms
Transfer 16 KB
Monthly Cost £3/mo
cdn.polarbyte.com
Other
Costly
Execution 206ms
Transfer 137 KB
Unused 80%
Monthly Cost £2/mo
securepubads.g.doubleclick.net
Other
Optional
Execution 182ms
Transfer 188 KB
Unused 76%
Monthly Cost £2/mo
cdn.polarbyte.com
Other
Optional
Execution 138ms
Transfer 85 KB
Unused 51%
Monthly Cost £1/mo
html-load.com
Other
Optional
Execution 112ms
Transfer 42 KB
Monthly Cost £1/mo
securepubads.g.doubleclick.net
Other
Optional
Execution 82ms
Transfer 34 KB
Monthly Cost £1/mo
pagead2.googlesyndication.com
Other
Optional
Execution 68ms
Transfer 0 KB
Unused 64%
Monthly Cost £1/mo

These scripts may cost more than they're worth

  • Unattributable adds 449ms and costs ~£5/month
  • www.oxfordlearnersdictionaries.com adds 333ms and costs ~£3/month
  • www.oxfordlearnersdictionaries.com adds 276ms and costs ~£3/month
  • cdn.polarbyte.com adds 206ms and costs ~£2/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

Unattributable takes 449ms 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.oxfordlearnersdictionaries.com takes 333ms 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

77% of www.oxfordlearnersdictionaries.com'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

www.oxfordlearnersdictionaries.com takes 276ms 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

cdn.polarbyte.com takes 206ms 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

80% of cdn.polarbyte.com'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

76% of securepubads.g.doubleclick.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

51% of cdn.polarbyte.com'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

64% of pagead2.googlesyndication.com'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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