Edx.org Site Title
Build new skills. Advance your career. | edX
Edx.org Meta Description
Discover thousands of offerings — from free courses to full degrees — delivered by world-class partners like Harvard, Google, Amazon and more.
Edx.org Test Results
Edx.org Mobile Performance: 37/100
Quick overview:
Opportunities
These suggestions can help your page load faster. They don't directly affect the Performance score.
Remove unused JavaScript. Potential savings of 339 KiB
Remove unused JavaScript to reduce bytes consumed by network activity. Learn more.
Defer offscreen images. Potential savings of 91 KiB
Consider lazy-loading offscreen and hidden images after all critical resources have finished loading to lower time to interactive. Learn more.
Avoid serving legacy JavaScript to modern browsers. Potential savings of 34 KiB
Polyfills and transforms enable legacy browsers to use new JavaScript features. However, many aren't necessary for modern browsers. For your bundled JavaScript, adopt a modern script deployment strategy using module/nomodule feature detection to reduce the amount of code shipped to modern browsers, while retaining support for legacy browsers. Learn More
Diagnostics
More information about the performance of your application. These numbers don't directly affect the Performance score.
Ensure text remains visible during webfont load
Leverage the font-display CSS feature to ensure text is user-visible while webfonts are loading. Learn more.
Reduce the impact of third-party code
Third-party code blocked the main thread for 460 ms
Third-party code can significantly impact load performance. Limit the number of redundant third-party providers and try to load third-party code after your page has primarily finished loading. Learn more.
Avoid `document.write()`
For users on slow connections, external scripts dynamically injected via `document.write()` can delay page load by tens of seconds. Learn more.
Minimize main-thread work
6.9 s
Consider reducing the time spent parsing, compiling and executing JS. You may find delivering smaller JS payloads helps with this. Learn more
Serve static assets with an efficient cache policy
17 resources found
A long cache lifetime can speed up repeat visits to your page. Learn more.
Reduce JavaScript execution time
4.3 s
Consider reducing the time spent parsing, compiling, and executing JS. You may find delivering smaller JS payloads helps with this. Learn more.
Largest Contentful Paint element
1 element found
This is the largest contentful element painted within the viewport. Learn More
Keep request counts low and transfer sizes small
95 requests • 1,479 KiB
To set budgets for the quantity and size of page resources, add a budget.json file. Learn more.
Avoid chaining critical requests
3 chains found
The Critical Request Chains below show you what resources are loaded with a high priority. Consider reducing the length of chains, reducing the download size of resources, or deferring the download of unnecessary resources to improve page load. Learn more.
Avoid long main-thread tasks
20 long tasks found
Lists the longest tasks on the main thread, useful for identifying worst contributors to input delay. Learn more
Avoid large layout shifts
4 elements found
These DOM elements contribute most to the CLS of the page.
Edx.org Mobile SEO: 81/100
Quick overview:
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.
Tap targets are not sized appropriately
30% appropriately sized tap targets
Interactive elements like buttons and links should be large enough (48x48px), and have enough space around them, to be easy enough to tap without overlapping onto other elements. Learn more.
Content Best Practices
Format your HTML in a way that enables crawlers to better understand your app’s content.
Document doesn't have a valid `hreflang`
hreflang links tell search engines what version of a page they should list in search results for a given language or region. Learn more.
Links do not have descriptive text
2 links found
Descriptive link text helps search engines understand your content. Learn more.
Edx.org Mobile Best Practices: 64/100
Quick overview:
General
Browser errors were logged to the console
Errors logged to the console indicate unresolved problems. They can come from network request failures and other browser concerns. Learn more
Registers an `unload` listener
The `unload` event does not fire reliably and listening for it can prevent browser optimizations like the Back-Forward Cache. Consider using the `pagehide` or `visibilitychange` events instead. Learn More
Trust and Safety
Includes front-end JavaScript libraries with known security vulnerabilities
1 vulnerability detected
Some third-party scripts may contain known security vulnerabilities that are easily identified and exploited by attackers. Learn more.
Does not use HTTPS
2 insecure requests found
All sites should be protected with HTTPS, even ones that don't handle sensitive data. This includes avoiding mixed content, where some resources are loaded over HTTP despite the initial request being servedover HTTPS. HTTPS prevents intruders from tampering with or passively listening in on the communications between your app and your users, and is a prerequisite for HTTP/2 and many new web platform APIs. Learn more.
User Experience
Serves images with low resolution
Image natural dimensions should be proportional to the display size and the pixel ratio to maximize image clarity. Learn more.
Edx.org Mobile Progressive Web App: 21/100
Quick overview:
PWA Optimized
Is not configured for a custom splash screen
A themed splash screen ensures a high-quality experience when users launch your app from their homescreens. Learn more. Failures: No manifest was fetched.
Does not provide a valid `apple-touch-icon`
For ideal appearance on iOS when users add a progressive web app to the home screen, define an `apple-touch-icon`. It must point to a non-transparent 192px (or 180px) square PNG. Learn More.
Manifest doesn't have a maskable icon
A maskable icon ensures that the image fills the entire shape without being letterboxed when installing the app on a device. Learn more. No manifest was fetched
Does not set a theme color for the address bar.
The browser address bar can be themed to match your site. Learn more. Failures: No manifest was fetched,
No `<meta name="theme-color">` tag found.
Fast and reliable
`start_url` does not respond with a 200 when offline
A service worker enables your web app to be reliable in unpredictable network conditions. Learn more. No usable web app manifest found on page.
Page load is not fast enough on mobile networks
Interactive at 14.6 s
A fast page load over a cellular network ensures a good mobile user experience. Learn more. Your page loads too slowly and is not interactive within 10 seconds. Look at the opportunities and diagnostics in the "Performance" section to learn how to improve.
Current page does not respond with a 200 when offline
If you're building a Progressive Web App, consider using a service worker so that your app can work offline. Learn more.
Installable
Does not register a service worker that controls page and `start_url`
The service worker is the technology that enables your app to use many Progressive Web App features, such as offline, add to homescreen, and push notifications. Learn more.
Does not use HTTPS
2 insecure requests found
All sites should be protected with HTTPS, even ones that don't handle sensitive data. This includes avoiding mixed content, where some resources are loaded over HTTP despite the initial request being servedover HTTPS. HTTPS prevents intruders from tampering with or passively listening in on the communications between your app and your users, and is a prerequisite for HTTP/2 and many new web platform APIs. Learn more.
Web app manifest does not meet the installability requirements
Browsers can proactively prompt users to add your app to their homescreen, which can lead to higher engagement. Learn more. Failures: No manifest was fetched.
Edx.org Mobile Accessibility: 94/100
Quick overview:
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.
`[aria-*]` attributes do not match their roles
Each ARIA `role` supports a specific subset of `aria-*` attributes. Mismatching these invalidates the `aria-*` attributes. Learn more.
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