Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.

SCORE

GRADE

FIX

REVIEW

PASS

INFO

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

Mobile Desktop

Performance

Accessibility

Best Practices

SEO

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

2.71 s

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

4.58 s

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

6.95 s

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

0.001

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

10.79 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.

41.38 s

Page Load Progression

1.1 s

2.1 s

3.2 s

4.2 s

5.3 s

6.3 s

7.4 s

8.4 s

Checks

8 PASS 1 REVIEW 6 FIX

Page Weight Budget

Action

4.1 MB transferred, 300 requests

FIX

4.1 MB transferred, 300 requests

Page weighs 11.6 MB (4.1 MB transferred)

JavaScript is 3.0 MB — consider code splitting or lazy loading

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

Got: 3.0 MB

300 HTTP requests — consider bundling or reducing

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Estimated 0.85 g CO2 per page load

4.1 MB transferred

300 requests

0.85 g CO2 per page load

JavaScript 3.0 MiB 75%

Images 756.5 KiB 18%

HTML 175.9 KiB 4%

Fonts 49.0 KiB 1%

Other 35.4 KiB 1%

Other 17.7 KiB 0%

Other 5.7 KiB 0%

Other 3.4 KiB 0%

CSS 1.4 KiB 0%

Other 0 B 0%

0 2.4 MB 4.9 MB

Over budget

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

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Why this matters

High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.

Source: web.dev

Third-Party Impact

Action

100% third-party, 0 ms blocking

FIX

100% third-party, 0 ms blocking

Third-party code accounts for 100% of page weight (4.1 MiB of 4.1 MiB)

Third-party blocking time is low (0 ms)

100%

First-party Third-party

JS Execution Cost

Action

13816ms total JS execution

FIX

13816ms total JS execution

https://www1.grouponcdn.com/next-pwa-app/assets/_n...: 5147ms CPU time

Unattributable: 1294ms CPU time

https://www.groupon.com/: 1256ms CPU time

https://www1.grouponcdn.com/next-pwa-app/assets/_n...: 1002ms CPU time

https://www1.grouponcdn.com/next-pwa-app/assets/_n...: 538ms CPU time

Third-party scripts: 13816ms (100% of total)

Main Thread Breakdown

Script Evaluation 71% Other 12% Style & Layout 6% Script Parsing & Compilation 6%

Script	Total	Scripting	Parse/Compile	Party
https://www1.grouponcdn.com/next-pwa-app/assets/_next/static/chunks/02z339zfz9esd.js	5147ms	4688ms	33ms	3rd
Unattributable	1294ms	325ms	0ms	3rd
https://www.groupon.com/	1256ms	39ms	9ms	3rd
https://www1.grouponcdn.com/next-pwa-app/assets/_next/static/chunks/0~g1a8gr6tx7u.js	1002ms	483ms	14ms	3rd
https://www1.grouponcdn.com/next-pwa-app/assets/_next/static/chunks/turbopack-0s8w5_chk~pvl.js	538ms	536ms	1ms	3rd
https://www1.grouponcdn.com/next-pwa-app/assets/_next/static/chunks/0cudc0zj.nnnn.js	449ms	303ms	15ms	3rd
https://www.googletagmanager.com/gtm.js?id=GTM-B76Z	423ms	368ms	52ms	3rd
https://www.googletagmanager.com/gtag/js?id=G-TW2CBMFZ20&cx=c&gtm=4e64k0h2	419ms	377ms	38ms	3rd
https://www1.grouponcdn.com/next-pwa-app/assets/_next/static/chunks/turbopack-01f38wd4pekmf.js	339ms	337ms	1ms	3rd
https://booster-dl.groupon.com/clients/groupon_us/data_gatherer.js	292ms	249ms	31ms	3rd

Showing top 10 of 27 scripts

JS Bundles

Action

138 scripts, 808 KB unused

FIX

138 scripts, 808 KB unused

https://accounts.google.com/gsi/client: 81 KB unused (85%)

Consider code splitting or tree shaking to reduce unused code.

https://www1.grouponcdn.com/next-pwa-app/assets/_n...: 70 KB unused (81%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtag/js?id=G-TW2C...: 65 KB unused (39%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtag/js?id=AW-732...: 62 KB unused (46%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtag/destination?...: 61 KB unused (46%)

Consider code splitting or tree shaking to reduce unused code.

Total unused JavaScript: 808 KB

808 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://accounts.google.com/gsi/client	96 KB	81 KB (85%)	✓	3rd
https://www1.grouponcdn.com/next-pwa-app/assets/_next/static/chunks/0bf6ehlvjjr3s.js	87 KB	70 KB (81%)	✓	3rd
https://www.googletagmanager.com/gtag/js?id=G-TW2CBMFZ20&cx=c&gtm=4e64k0h2	168 KB	65 KB (39%)	✓	3rd
https://www.googletagmanager.com/gtag/js?id=AW-732782318&cx=c&gtm=4e64k0h2	134 KB	62 KB (46%)	✓	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-987034343&cx=c&gtm=4e64k0h2	134 KB	61 KB (46%)	✓	3rd
https://www.googletagmanager.com/gtag/js?id=AW-1013899312&cx=c&gtm=4e64k0h2	146 KB	61 KB (42%)	✓	3rd
https://www.googletagmanager.com/gtag/js?id=AW-849832365&cx=c&gtm=4e64k0h2	138 KB	61 KB (44%)	✓	3rd
https://www.googletagmanager.com/gtm.js?id=GTM-B76Z	197 KB	54 KB (27%)	✓	3rd
https://www1.grouponcdn.com/next-pwa-app/assets/_next/static/chunks/0zruk7p808a-7.js	131 KB	48 KB (37%)	✓	3rd
https://connect.facebook.net/signals/config/1644470949134066?v=2.9.303&r=stable&domain=www.groupon.com&hme=97937018cefade17726f0472876fc101316b2ce9008a35a6a5a7977d7436151a&ex_m=104%2C205%2C154%2C22%2C72%2C73%2C145%2C68%2C67%2C11%2C162%2C90%2C16%2C138%2C127%2C39%2C75%2C78%2C134%2C159%2C164%2C8%2C4%2C5%2C7%2C6%2C3%2C91%2C101%2C165%2C170%2C219%2C62%2C186%2C187%2C55%2C276%2C30%2C74%2C231%2C230%2C229%2C23%2C33%2C103%2C61%2C10%2C63%2C97%2C98%2C99%2C105%2C130%2C31%2C29%2C132%2C133%2C129%2C128%2C155%2C76%2C158%2C156%2C157%2C50%2C60%2C123%2C15%2C161%2C45%2C263%2C264%2C262%2C26%2C27%2C28%2C48%2C146%2C77%2C112%2C18%2C20%2C44%2C40%2C42%2C41%2C83%2C92%2C96%2C110%2C144%2C147%2C46%2C111%2C24%2C21%2C119%2C69%2C36%2C149%2C148%2C150%2C141%2C139%2C25%2C35%2C59%2C109%2C160%2C70%2C17%2C152%2C114%2C81%2C66%2C19%2C85%2C86%2C116%2C84%2C136%2C135%2C34%2C278%2C293%2C212%2C201%2C202%2C200%2C296%2C288%2C52%2C213%2C107%2C131%2C80%2C121%2C54%2C47%2C49%2C113%2C120%2C126%2C58%2C64%2C151%2C115%2C37%2C32%2C53%2C56%2C100%2C163%2C1%2C124%2C14%2C122%2C12%2C2%2C57%2C93%2C65%2C118%2C89%2C88%2C166%2C167%2C94%2C95%2C9%2C125%2C102%2C51%2C142%2C87%2C79%2C71%2C117%2C106%2C43%2C143%2C0%2C82%2C137%2C140%2C153%2C38%2C108%2C13%2C168	127 KB	35 KB (28%)	✓	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

Page Weight Inventory

Action

300 resources · 4.1 MB · 808 KB savings available

FIX

300 resources · 4.1 MB · 808 KB savings available

Page weight 3.1 MB over 1MB target

Got: 4.1 MB Expected: ≤ 1 MB

~808 KB of savings available

299 third-party resources (100% of weight)

1 resources over 200KB

300 resources · 4.1 MiB · 299 third-party 3.1 MiB over 1MB target

JavaScript 75% · 3.0 MiB

Image 18% · 762.5 KiB

Document 4% · 180.9 KiB

Other 1% · 51.2 KiB

Font 1% · 49.0 KiB

CSS 0% · 1.4 KiB

~807.7 KiB of savings available

Remove unused JavaScript: 807.7 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

300 resources			4.1 MiB

HTTP Caching

Action

No cache headers

FIX

No cache headers

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.

Image Optimization

60 images, 0 KB saveable

REVIEW

60 images, 0 KB saveable

https://img.grouponcdn.com/message-service/QoEApfk... is missing width/height — may cause layout shift

Set explicit width and height to prevent CLS.

60 images 757 KB

0 oversized -0 KB

46 legacy format

1 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

A+

Text Compression

All text resources are compressed

PASS

All text resources are compressed

All text resources are properly compressed.

A+

Font Loading

2 fonts (49 KB)

PASS

2 fonts (49 KB)

2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

49 KB total

Render-blocking

of 2

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

f141b5b7abe57afc-s.p.0-... woff2 swap

Size 31 KB

Load time 148 ms

Start 1.0 s

Risk FOUT — text flashes from fallback to web font

0c8f209abc35ee02-s.p.03... woff2 swap

Size 18 KB

Load time 148 ms

Start 1.0 s

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

No caching issues found

All static resources have appropriate caching headers.

A+

Critical Rendering Path

No render-blocking resources

PASS

No render-blocking resources

No render-blocking resources detected

A+

Resource Hints

5 hints, 0 missing preconnects

PASS

5 hints, 0 missing preconnects

Page uses 5 resource hint(s)

Current Resource Hints

preconnect

—

preload

dns-prefetch

—

prefetch

—

5 resource hints configured

A+

Render-Blocking Resources

No render-blocking resources detected

PASS

No render-blocking resources detected

No render-blocking resources detected in <head>

A+

Third-Party Resources

No third-party resources detected

PASS

No third-party resources 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

300 requests over 7099ms

INFO

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 13816ms · 1795KB · €221/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
www1.grouponcdn.com www1.grouponcdn.com	Other	5147ms	56 KB	—	€82/mo	Costly
Unattributable Unattributable	Other	1294ms	0 KB	—	€21/mo	Costly
www.groupon.com www.groupon.com	Other	1256ms	165 KB	—	€20/mo	Costly
www1.grouponcdn.com www1.grouponcdn.com	Other	1002ms	47 KB	—	€16/mo	Costly
www1.grouponcdn.com www1.grouponcdn.com	Other	538ms	5 KB	—	€9/mo	Costly
www1.grouponcdn.com www1.grouponcdn.com	Other	449ms	64 KB	42%	€7/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	423ms	197 KB	27%	€7/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	419ms	168 KB	39%	€7/mo	Costly
www1.grouponcdn.com www1.grouponcdn.com	Other	339ms	5 KB	—	€5/mo	Costly
booster-dl.groupon.com booster-dl.groupon.com	Other	292ms	30 KB	—	€5/mo	Costly
Facebook Pixel connect.facebook.net	Advertising	276ms	127 KB	28%	€4/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	264ms	146 KB	42%	€4/mo	Costly
www1.grouponcdn.com www1.grouponcdn.com	Other	263ms	11 KB	—	€4/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	235ms	138 KB	44%	€4/mo	Costly
Microsoft Clarity scripts.clarity.ms	Session Replay	201ms	26 KB	—	€3/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	197ms	134 KB	46%	€3/mo	Optional
Google Tag Manager www.googletagmanager.com	Tag Manager	186ms	134 KB	46%	€3/mo	Optional
cdn.attn.tv cdn.attn.tv	Other	179ms	49 KB	59%	€3/mo	Optional
static.cloudflareinsights.com static.cloudflareinsights.com	Other	155ms	0 KB	—	€2/mo	Optional
Facebook Pixel connect.facebook.net	Advertising	120ms	97 KB	33%	€2/mo	Optional
b-code.liadm.com b-code.liadm.com	Other	120ms	47 KB	—	€2/mo	Optional
guard-svc.groupon.com guard-svc.groupon.com	Other	116ms	17 KB	—	€2/mo	Optional
dynamic.criteo.com dynamic.criteo.com	Other	90ms	25 KB	—	€1/mo	Optional
www.groupon.com www.groupon.com	Other	82ms	6 KB	—	€1/mo	Optional
cdn.id5-sync.com cdn.id5-sync.com	Other	69ms	35 KB	—	€1/mo	Optional
api.exponea.com api.exponea.com	Other	56ms	52 KB	43%	€1/mo	Optional
www.mczbf.com www.mczbf.com	Other	50ms	13 KB	—	€1/mo	Optional

www1.grouponcdn.com

Other

Costly

Execution 5147ms

Transfer 56 KB

Monthly Cost €82/mo

Unattributable

Other

Costly

Execution 1294ms

Transfer 0 KB

Monthly Cost €21/mo

www.groupon.com

Other

Costly

Execution 1256ms

Transfer 165 KB

Monthly Cost €20/mo

www1.grouponcdn.com

Other

Costly

Execution 1002ms

Transfer 47 KB

Monthly Cost €16/mo

www1.grouponcdn.com

Other

Costly

Execution 538ms

Transfer 5 KB

Monthly Cost €9/mo

www1.grouponcdn.com

Other

Costly

Execution 449ms

Transfer 64 KB

Unused 42%

Monthly Cost €7/mo

Google Tag Manager

Tag Manager

Costly

Execution 423ms

Transfer 197 KB

Unused 27%

Monthly Cost €7/mo

Google Tag Manager

Tag Manager

Costly

Execution 419ms

Transfer 168 KB

Unused 39%

Monthly Cost €7/mo

www1.grouponcdn.com

Other

Costly

Execution 339ms

Transfer 5 KB

Monthly Cost €5/mo

booster-dl.groupon.com

Other

Costly

Execution 292ms

Transfer 30 KB

Monthly Cost €5/mo

Facebook Pixel

Advertising

Costly

Execution 276ms

Transfer 127 KB

Unused 28%

Monthly Cost €4/mo

Google Tag Manager

Tag Manager

Costly

Execution 264ms

Transfer 146 KB

Unused 42%

Monthly Cost €4/mo

www1.grouponcdn.com

Other

Costly

Execution 263ms

Transfer 11 KB

Monthly Cost €4/mo

Google Tag Manager

Tag Manager

Costly

Execution 235ms

Transfer 138 KB

Unused 44%

Monthly Cost €4/mo

Microsoft Clarity

Session Replay

Costly

Execution 201ms

Transfer 26 KB

Monthly Cost €3/mo

Google Tag Manager

Tag Manager

Optional

Execution 197ms

Transfer 134 KB

Unused 46%

Monthly Cost €3/mo

Google Tag Manager

Tag Manager

Optional

Execution 186ms

Transfer 134 KB

Unused 46%

Monthly Cost €3/mo

cdn.attn.tv

Other

Optional

Execution 179ms

Transfer 49 KB

Unused 59%

Monthly Cost €3/mo

static.cloudflareinsights.com

Other

Optional

Execution 155ms

Transfer 0 KB

Monthly Cost €2/mo

Facebook Pixel

Advertising

Optional

Execution 120ms

Transfer 97 KB

Unused 33%

Monthly Cost €2/mo

b-code.liadm.com

Other

Optional

Execution 120ms

Transfer 47 KB

Monthly Cost €2/mo

guard-svc.groupon.com

Other

Optional

Execution 116ms

Transfer 17 KB

Monthly Cost €2/mo

dynamic.criteo.com

Other

Optional

Execution 90ms

Transfer 25 KB

Monthly Cost €1/mo

www.groupon.com

Other

Optional

Execution 82ms

Transfer 6 KB

Monthly Cost €1/mo

cdn.id5-sync.com

Other

Optional

Execution 69ms

Transfer 35 KB

Monthly Cost €1/mo

api.exponea.com

Other

Optional

Execution 56ms

Transfer 52 KB

Unused 43%

Monthly Cost €1/mo

www.mczbf.com

Other

Optional

Execution 50ms

Transfer 13 KB

Monthly Cost €1/mo

These scripts may cost more than they're worth

www1.grouponcdn.com adds 5147ms and costs ~€82/month
Unattributable adds 1294ms and costs ~€21/month
www.groupon.com adds 1256ms and costs ~€20/month
www1.grouponcdn.com adds 1002ms and costs ~€16/month
www1.grouponcdn.com adds 538ms and costs ~€9/month
www1.grouponcdn.com adds 449ms and costs ~€7/month
Google Tag Manager adds 423ms and costs ~€7/month
Google Tag Manager adds 419ms and costs ~€7/month
www1.grouponcdn.com adds 339ms and costs ~€5/month
booster-dl.groupon.com adds 292ms and costs ~€5/month
Facebook Pixel adds 276ms and costs ~€4/month
Google Tag Manager adds 264ms and costs ~€4/month
www1.grouponcdn.com adds 263ms and costs ~€4/month
Google Tag Manager adds 235ms and costs ~€4/month
Microsoft Clarity adds 201ms 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

www1.grouponcdn.com takes 5147ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters