Access cs50.harvard.edu. CS50: Computer Science Courses and Programs from Harvard | edX

cs50.harvard.edu screenshot

18

Performance

Renders faster than
34% of other websites
96

Accessibility

Visual factors better than
that of 88% of websites
83

Best Practices

More advanced features
available than in
55% of websites
75

SEO

Google-friendlier than
32% of websites

First Response

33 ms

Resources Loaded

1.5 sec

Page Rendered

2.3 sec

cs50.harvard.edu screenshot

About Website

Visit cs50.harvard.edu now to see the best up-to-date CS50 Harvard content for United States and also check out these interesting facts you probably never knew about cs50.harvard.edu

Introduction to Computer Science from Harvard, better known as CS50, is the largest course on the Harvard campus and more than 4,000,000 learners worldwide have registered for the course on edX.

Visit cs50.harvard.edu

Key Findings

We analyzed Cs50.harvard.edu page load time and found that the first response time was 33 ms and then it took 3.8 sec to load all DOM resources and completely render a web page. This is a poor result, as 65% of websites can load faster.

name

value

score

weighting

FCP (First Contentful Paint)

Value13.7 s

0/100

10%

LCP (Largest Contentful Paint)

Value18.4 s

0/100

25%

SI (Speed Index)

Value14.1 s

1/100

10%

TBT (Total Blocking Time)

Value1,680 ms

11/100

30%

CLS (Cumulative Layout Shift)

Value0

100/100

15%

TTI (Time to Interactive)

Value28.9 s

0/100

10%

cs50.harvard.edu

33 ms

cs50.harvard.edu

17 ms

92 ms

webfont.js

38 ms

jquery.min.js

62 ms

Our browser made a total of 359 requests to load all elements on the main page. We found that 6% of them (21 requests) were addressed to the original Cs50.harvard.edu, 64% (230 requests) were made to Img.youtube.com and 28% (101 requests) were made to Ka-p.fontawesome.com. The less responsive or slowest element that took the longest time to load (507 ms) relates to the external source Video.cs50.io.

Content Size

3.9 MB

After Optimization

3.4 MB

In fact, the total size of Cs50.harvard.edu main page is 3.9 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. Only a small number of websites need less resources to load. Images take 1.7 MB which makes up the majority of the site volume.

HTML Optimization

-90%

Potential reduce by 345.7 kB

Original 382.8 kB
After minification 379.1 kB
After compression 37.1 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 345.7 kB or 90% of the original size.

Image Optimization

-0%

Potential reduce by 266 B

Original 1.7 MB
After minification 1.7 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. CS50 Harvard images are well optimized though.

JavaScript Optimization

-10%

Potential reduce by 163.1 kB

Original 1.6 MB
After minification 1.6 MB
After compression 1.4 MB

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. This website has mostly compressed JavaScripts.

CSS Optimization

-2%

Potential reduce by 7.1 kB

Original 303.9 kB
After minification 303.9 kB
After compression 296.7 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. Cs50.harvard.edu has all CSS files already compressed.

Requests Now

258

After Optimization

230

The browser has sent 258 CSS, Javascripts, AJAX and image requests in order to completely render the main page of CS50 Harvard. We recommend that multiple CSS and JavaScript files should be merged into one by each type, as it can help reduce assets requests from 19 to 1 for JavaScripts and from 11 to 1 for CSS and as a result speed up the page load time.

Accessibility Issues

These are opportunities to improve the legibility of your content.

High

Background and foreground colors do not have a sufficient contrast ratio.

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.

High

<frame> or <iframe> elements do not have a title

Areas of Improvement

High

Does not use HTTPS

Low

Ensure CSP is effective against XSS attacks

Low

Detected JavaScript libraries

High

Browser errors were logged to the console

High

Missing source maps for large first-party JavaScript

Search Engine Optimization Advices

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

High

Links do not have descriptive text

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

High

Links are not crawlable

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/).

High

Document uses legible font sizes

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 Cs50.harvard.edu 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 Cs50.harvard.edu 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

cs50.harvard.edu

Open Graph data is detected on the main page of CS50 Harvard. This is the best way to make the web page social media friendly. Here is how it looks like on Facebook: