1.1 sec in total
13 ms
767 ms
365 ms
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Visit preview.edx.orgWe analyzed Preview.edx.org page load time and found that the first response time was 13 ms and then it took 1.1 sec to load all DOM resources and completely render a web page. This is quite a good result, as only 20% of websites can load faster.
preview.edx.org performance score
name
value
score
weighting
Value5.0 s
9/100
10%
Value6.1 s
12/100
25%
Value12.7 s
3/100
10%
Value4,280 ms
1/100
30%
Value0.159
73/100
15%
Value25.3 s
0/100
10%
13 ms
52 ms
9 ms
27 ms
49 ms
Our browser made a total of 70 requests to load all elements on the main page. We found that 1% of them (1 request) were addressed to the original Preview.edx.org, 73% (51 requests) were made to Edx.org and 9% (6 requests) were made to D37djvu3ytnwxt.cloudfront.net. The less responsive or slowest element that took the longest time to load (214 ms) relates to the external source Courses.edx.org.
Page size can be reduced by 826.9 kB (45%)
1.9 MB
1.0 MB
In fact, the total size of Preview.edx.org main page is 1.9 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. 65% of websites need less resources to load. Images take 791.1 kB which makes up the majority of the site volume.
Potential reduce by 70.9 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. This page needs HTML code to be minified as it can gain 10.0 kB, which is 12% of the original size. It is highly recommended that content of this web page should be compressed using GZIP, as it can save up to 70.9 kB or 84% of the original size.
Potential reduce by 53.0 kB
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. Preview EdX images are well optimized though.
Potential reduce by 405.7 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 405.7 kB or 65% of the original size.
Potential reduce by 297.3 kB
CSS files minification is very important to reduce a web page rendering time. The faster CSS files can load, the earlier a page can be rendered. Preview.edx.org needs all CSS files to be minified and compressed as it can save up to 297.3 kB or 83% of the original size.
Number of requests can be reduced by 19 (28%)
67
48
The browser has sent 67 CSS, Javascripts, AJAX and image requests in order to completely render the main page of Preview EdX. We recommend that multiple CSS and JavaScript files should be merged into one by each type, as it can help reduce assets requests from 16 to 1 for JavaScripts and from 5 to 1 for CSS and as a result speed up the page load time.
preview.edx.org
13 ms
www.edx.org
52 ms
css_xE-rWrJf-fncB6ztZfd2huxqgxu4WO-qwma6Xer30m4.css
9 ms
css_mktzIRd5CRE-97qJhrh-LyZqgbhTe9MZCqn-bCpDQ_g.css
27 ms
css_itfpFncbaobjsalM8t20UKaSALUpAW_znMsrRO3KgU0.css
49 ms
js_-z-2lAhufzBeVjYseT6cTzSICUy9vnoLBpu1sF_zZrs.js
48 ms
1743970571.js
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js_OWqT85P6-BA03fclrtuha8brsVbYzL0dixQfV1mVyxc.js
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js_ED5CXIEwhB9PDdZv7AOYZUbFBi9KCcPctIWjP4xzd14.js
28 ms
require.js
28 ms
js_7lBERWulILh4tvuDYUTN54nLRRmvhKk1J3kWNWsPYhw.js
37 ms
backbone-min.js
38 ms
discovery_card_block.js
38 ms
home_page.js
83 ms
event
172 ms
analytics.min.js
124 ms
edx-logo-header.png
92 ms
footer
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OpenSans-Regular-webfont.woff
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OpenSans-Light-webfont.woff
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OpenSans-Semibold-webfont.woff
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OpenSans-Bold-webfont.woff
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homepage-hero-lg.jpg
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fontawesome-webfont.woff
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analytics.js
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gtm.js
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dj_.js
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mit_logo_200x101_0.png
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cards
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harvard_logo_200x101_0.png
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berkeley_logo_200x101_0.png
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app_store_badge_135x40.d0558d910630.svg
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linkid.js
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lfx101_linux_course_card-378x225.jpg
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collect
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verified.png
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nr-768.min.js
107 ms
preview.edx.org accessibility score
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
[aria-*] attributes do not match their roles
Elements with an ARIA [role] that require children to contain a specific [role] are missing some or all of those required children.
[role]s are not contained by their required parent element
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
Buttons do not have an accessible 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
Lists do not contain only <li> elements and script supporting elements (<script> and <template>).
preview.edx.org best practices score
Trust and Safety
Impact
Issue
Does not use HTTPS
Ensure CSP is effective against XSS attacks
General
Impact
Issue
Detected JavaScript libraries
Browser errors were logged to the console
Page has valid source maps
preview.edx.org SEO score
Content Best Practices
Format your HTML in a way that enables crawlers to better understand your app’s content.
Impact
Issue
Links do not have descriptive text
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
Document uses legible font sizes
EN
EN
UTF-8
Language claimed in HTML meta tag should match the language actually used on the web page. Otherwise Preview.edx.org 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 Preview.edx.org 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.
preview.edx.org
Open Graph data is detected on the main page of Preview EdX. This is the best way to make the web page social media friendly. Here is how it looks like on Facebook: