Tools & Wizards About Us
costco.co.uk screenshot

Report Summary

  • 18

    Performance

    Renders faster than
    34% of other websites

  • 73

    Accessibility

    Visual factors better than
    that of 38% of websites

  • 67

    Best Practices

    More advanced features
    available than in
    24% of websites

  • 85

    SEO

    Google-friendlier than
    55% of websites

costco.co.uk

Join the club & start saving! | Costco UK

Page Load Speed

4.7 sec in total

First Response

273 ms

Resources Loaded

3.2 sec

Page Rendered

1.2 sec

costco.co.uk screenshot

About Website

Welcome to costco.co.uk homepage info - get ready to check Costco best content for United Kingdom right away, or after learning these important things about costco.co.uk

Shop at Costco.co.uk for best deals on all products and enjoy low warehouse prices on name-brand products online and instore. Delivery included.

Visit costco.co.uk

Key Findings

We analyzed Costco.co.uk page load time and found that the first response time was 273 ms and then it took 4.5 sec to load all DOM resources and completely render a web page. This is a poor result, as 70% of websites can load faster.

Performance Metrics

costco.co.uk performance score

18

Measured Metrics

name

value

score

weighting

FCP (First Contentful Paint)

Value3.2 s

42/100

10%

LCP (Largest Contentful Paint)

Value10.1 s

0/100

25%

SI (Speed Index)

Value10.4 s

8/100

10%

TBT (Total Blocking Time)

Value5,080 ms

0/100

30%

CLS (Cumulative Layout Shift)

Value0.121

84/100

15%

TTI (Time to Interactive)

Value23.1 s

1/100

10%

Network Requests Diagram

costco.co.uk

273 ms

costco.co.uk

130 ms

www.costco.co.uk

648 ms

styles.f3a189f94df19dabe8c5.css

60 ms

costco_responsive_spa.css

45 ms

Our browser made a total of 124 requests to load all elements on the main page. We found that 98% of them (122 requests) were addressed to the original Costco.co.uk, 2% (2 requests) were made to Mobilecontent.costco.com. The less responsive or slowest element that took the longest time to load (1.2 sec) belongs to the original domain Costco.co.uk.

Page Optimization Overview & Recommendations

Page size can be reduced by 1.2 MB (26%)

Content Size

4.8 MB

After Optimization

3.5 MB

  • HTML
  • Images
  • JavaScript

In fact, the total size of Costco.co.uk main page is 4.8 MB. This result falls beyond the top 1M of websites and identifies a large and not optimized web page that may take ages to load. 70% of websites need less resources to load. Images take 3.7 MB which makes up the majority of the site volume.

HTML Optimization

-92%

Potential reduce by 992.1 kB

  • Original 1.1 MB
  • After minification 1.0 MB
  • After compression 85.4 kB

HTML content can be minified and compressed by a website’s server. The most efficient way is to compress content using GZIP which reduces data amount travelling through the network between server and browser. HTML code on this page is well minified. It is highly recommended that content of this web page should be compressed using GZIP, as it can save up to 992.1 kB or 92% of the original size.

Image Optimization

-6%

Potential reduce by 217.8 kB

  • Original 3.7 MB
  • After minification 3.4 MB

Image size optimization can help to speed up a website loading time. The chart above shows the difference between the size before and after optimization. Costco images are well optimized though.

JavaScript Optimization

-67%

Potential reduce by 17.8 kB

  • Original 26.7 kB
  • After minification 26.7 kB
  • After compression 8.8 kB

It’s better to minify JavaScript in order to improve website performance. The diagram shows the current total size of all JavaScript files against the prospective JavaScript size after its minification and compression. It is highly recommended that all JavaScript files should be compressed and minified as it can save up to 17.8 kB or 67% of the original size.

Requests Breakdown

Number of requests can be reduced by 7 (6%)

Requests Now

118

After Optimization

111

  • Images
  • JavaScript
  • CSS

The browser has sent 118 CSS, Javascripts, AJAX and image requests in order to completely render the main page of Costco. We recommend that multiple CSS and JavaScript files should be merged into one by each type, as it can help reduce assets requests from 8 to 1 for JavaScripts and as a result speed up the page load time.

Network Requests Diagram

costco.co.uk

costco.co.uk

273 ms

costco.co.uk

costco.co.uk

130 ms

www.costco.co.uk

www.costco.co.uk

648 ms

styles.f3a189f94df19dabe8c5.css

styles.f3a189f94df19dabe8c5.css

60 ms

costco_responsive_spa.css

costco_responsive_spa.css

45 ms

54c1a523

54c1a523

125 ms

runtime-es2015.057786f8bc767c478d63.js

runtime-es2015.057786f8bc767c478d63.js

44 ms

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runtime-es5.057786f8bc767c478d63.js

54 ms

polyfills-es5.5bc4af973696f427b941.js

polyfills-es5.5bc4af973696f427b941.js

140 ms

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72 ms

scripts.a3089741f744541363d4.js

scripts.a3089741f744541363d4.js

60 ms

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112 ms

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174 ms

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385 ms

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409 ms

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377 ms

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357 ms

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355 ms

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357 ms

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353 ms

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358 ms

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397 ms

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397 ms

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392 ms

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398 ms

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492 ms

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505 ms

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620 ms

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167 ms

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240 ms

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255 ms

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239 ms

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130 ms

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731 ms

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18 ms

Accessibility Review

costco.co.uk accessibility score

73

Accessibility Issues

ARIA

These are opportunities to improve the usage of ARIA in your application which may enhance the experience for users of assistive technology, like a screen reader.

Impact

Issue

High

[aria-*] attributes do not match their roles

High

ARIA IDs are not unique

Names and labels

These are opportunities to improve the semantics of the controls in your application. This may enhance the experience for users of assistive technology, like a screen reader.

Impact

Issue

High

Buttons do not have an accessible name

High

Image elements do not have [alt] attributes

High

Links do not have a discernible name

Tables and lists

These are opportunities to improve the experience of reading tabular or list data using assistive technology, like a screen reader.

Impact

Issue

High

Lists do not contain only <li> elements and script supporting elements (<script> and <template>).

Best Practices

costco.co.uk best practices score

67

Areas of Improvement

Trust and Safety

Impact

Issue

High

Does not use HTTPS

High

Includes front-end JavaScript libraries with known security vulnerabilities

Low

Ensure CSP is effective against XSS attacks

User Experience

Impact

Issue

High

Displays images with incorrect aspect ratio

General

Impact

Issue

Low

Detected JavaScript libraries

High

Browser errors were logged to the console

High

Missing source maps for large first-party JavaScript

SEO Factors

costco.co.uk SEO score

85

Search Engine Optimization Advices

Crawling and Indexing

To appear in search results, crawlers need access to your app.

Impact

Issue

High

Links are not crawlable

Content Best Practices

Format your HTML in a way that enables crawlers to better understand your app’s content.

Impact

Issue

High

Image elements do not have [alt] attributes

Mobile Friendly

Make sure your pages are mobile friendly so users don’t have to pinch or zoom in order to read the content pages. [Learn more](https://developers.google.com/search/mobile-sites/).

Impact

Issue

High

Document uses legible font sizes

High

Tap targets are not sized appropriately

Language and Encoding

  • Language Detected

    EN

  • Language Claimed

    EN

  • Encoding

    UTF-8

Language claimed in HTML meta tag should match the language actually used on the web page. Otherwise Costco.co.uk can be misinterpreted by Google and other search engines. Our service has detected that English is used on the page, and it matches the claimed language. Our system also found out that Costco.co.uk main page’s claimed encoding is utf-8. Use of this encoding format is the best practice as the main page visitors from all over the world won’t have any issues with symbol transcription.

Social Sharing Optimization

costco.co.uk

Open Graph data is detected on the main page of Costco. This is the best way to make the web page social media friendly. Here is how it looks like on Facebook: