Below are frequently asked questions (FAQs) specific to CS50x 2015. For FAQs specific to edX, see

Can I re-submit problem sets?

Yes, you may re-submit problem sets that you completed in 2014 for credit in 2015. To re-submit, simply follow the instructions under How to Submit in the specifications for each of CS50x 2015’s problem sets. However, know that some of 2015’s problem sets are different. Here’s what’s new in 2015.

Do I need a new appliance?

If you already have CS50 Appliance 19 (or even earlier) installed, yes, you will need CS50 Appliance 2014 for CS50x 2015.

To copy files from an older appliance to CS50 Appliance 2014, you’ll probably find it easiest to use Dropbox, as per the instructions in the CS50 Manual.

Does CS50x have deadlines?

Only one, when the course itself ends! You are welcome to take CS50x at your own pace, so long as you submit nine problem sets and submit a final project no later than 31 December 2015, per the schedule.

Does CS50x have office hours?

No, afraid CS50x is too large! However, office hours are available to students taking CS50 through Harvard College or Harvard Extension School. See

Does CS50x have quizzes?

No, only students taking CS50 through Harvard College or Harvard Extension School have quizzes!

Does CS50x offer Verified Certificates of Achievement?

Yes. CS50x offers Verified Certificates of Achievement through edX as well as a CS50 Certificate and course credit from Harvard Extension School.

Does CS50x offer tutoring?

CS50x itself does not offer tutoring but Harvard Student Agencies does (for a fee) at

How can I hide CS50’s Facebook Group from my newsfeed?

If you joined CS50’s Facebook Group but don’t want to see new posts in your newsfeed, hover over any of CS50’s posts in your newsfeed until screenshot appears in the post’s top-right corner, then select Unfollow CS50 from that menu, per the below. You’ll still be in the group, so you can still visit it at anytime you’d like. Note that old posts won’t disappear from your newsfeed (unless you remove them manually), but new posts will no longer appear. CS50 will thus gradually disappear from your newsfeed as other updates appear.


How can I play videos faster or slower?

If using Chrome, Firefox, or Safari (i.e., a browser that supports HTML5 and MP4), you should see a SPEED control below each video, per the below. If not, your browser might not support different speeds, in which case you can download the video (as via the blue links beneath it) and use a client-side player like VLC, whose Playback menu should allow you to alter playback speed. Beware, though, David talks fast at 1x, let alone 2x!