For answers to other questions, do just ask in any of CS50’s communities!


Does CS50x have a test or quiz?

Nope! CS50 at Harvard does have a test and quiz, but CS50x does not.

What’s the difference between “less comfortable” and “more comfortable” problems? Do I have to do both?

In some earlier problem sets, you’ll have a choice between a “less comfortable” and a “more comfortable” problem.

The “less comfortable” are what you might consider the “standard” version of the problem, designed for students who have little or no prior experience. The “more comfortable” are the “challenge” version, designed for students who consider themselves more comfortable due to prior study/experience before this class. As such, they may require more concepts than have been covered in the course so far.

If you find yourself really struggling with the “more comfortable” version, you should switch to the “less” version (or if you’ve already completed that, simply move on and perhaps revisit in a later week). It would be better for you to skip the problem than to become so frustrated as to drop out of the course entirely. For reference, in the Fall 2019 Harvard class, only 20-30% of students submitted the “more comfortable” problems.

You don’t get any extra points for doing the “more comfortable” problems. If you submit both, the one with the highest grade will count towards your overall course progress.

If I submitted a problem and did not reach the 70% passing grade, can I resubmit?

Yes! You may resubmit; we will only count your most recent submission towards your progress. See the Grades section below for more details.


I completed CS50x in 2022 (or prior). Why does my Gradebook no longer show me as having completed the course?

CS50x is a course that spans multiple years, but has a content refresh on 1 January each year. Your gradebook will only ever reflect your completion status of the current version of the course (which is now CS50x 2023), even if you have completed the course in a prior year. If you wish to get the green banner back, you can complete whatever assessments are missing for the current version of the course, but your free CS50 Certificate is still available at certificates.cs50.io, and eligibility for a Verified Certificate is unaffected so long as you saw the green banner atop your gradebook at least once.

Do I have to pay for verification before starting the course?

Nope! If you would like a verified certificate from edX, you can pay for verification at any point, even after completing all of the coursework. Though we do recommend, to avoid any logistical issues that can delay certificate issuance, that you verify before finishing the course. Otherwise, the 30-day wait we reference below only starts once you have had your identity verified by edX.

If I paid for a verified certificate before 2023, do I need to pay again?

No, your verification should be good for an entire year, but if it has expired, you should be able to re-verify yourself via edX’s dashboard.

How do I get my free CS50 Certificate?

Once you have completed the course and met all of the requirements, you’ll see a link on your CS50x Gradebook page allowing you to request a free CS50 Certificate, much like the one shown here. This link will be available within approximately four hours, and you should then proceed to log in using your GitHub credentials. If you have trouble accessing it, try logging out of GitHub and back in, then revisit the link to download your certificate. Be sure to request your certificate before 1 January 2024.

How do I get my verified certificate from edX?

Every few weeks, CS50’s staff provides edX with a list of students who have satisfied CS50x’s requirements (by receiving scores of at least 70% on every required problem submitted as part of the course’s ten problem sets, the nine labs, as well as on the final project). Typically within a week thereafter, edX then generates students’ Verified Certificates (for students who have active Verification), at which point they should appear automatically on edX’s dashboard. Note that edX will not notify you, so be sure to check your dashboard periodically.

If it has been more than a month since you met all requirements and you have still not received your certificate despite holding an active Verification that whole time, email certificates@cs50.harvard.edu with your details. Please do not email sooner; we cannot accept requests for expedited processing of Verified Certificates.

How do I know if I have completed all requirements for a certificate?

Your CS50x Gradebook shows the result for each 2023 problem submission and progress you have made for each week. When you have completed requirements for a given week, the week number will be shown in green, and your progress indicator will be updated to reflect that. Once you have completed all requirements, you will see a green banner atop that page, confirming your completion.

What’s the difference between a verified certificate and a CS50 Certificate?

A verified certificate, which you can purchase from edX, “can provide proof for an employer, school, or other institution that you have successfully completed an online course.”

A CS50 Certificate is a free certificate from CS50 itself.

How should I describe my verified certificate on my resume or elsewhere?

You’re welcome to say that you received a verified certificate from HarvardX.


If I don’t finish the course before 31 December 2023, what will happen?

On 1 January 2024, the course will be updated to a 2024 version. Your progress from 2023 will be carried forward to the 2024 version (see below). After 31 December 2023, you may only submit the 2024 version’s problem sets and will need to satisfy whatever requirements are in place for CS50x 2024. Your carryover progress (as described below) from 2022 or prior will not carry forward into 2024, however.

If I started CS50x before 2023, can I resume?

Yes, any progress you made on past years’ problem sets has been carried forward to your CS50x 2023 gradebook. Note that individual problem results from past years are not shown, but if the corresponding problem set and lab was completed, you’ll see it marked with a green circle and included in your progress bar at the top. Moving forward, though, you must submit CS50x 2023’s problem sets and labs. Work from prior versions of the course may not be submitted for credit.

Here is how you should transition from the 2022 course to the 2023 course:

Completed in 2022 Resume your studies with
No Problem Sets Week 0 and Problem Set 0 of CS50x 2023.
Problem Set 0 Week 1, Lab 1, and Problem Set 1 of CS50x 2023.
Problem Sets 0 – 1 Week 2, Lab 2, and Problem Set 2 of CS50x 2023.
Problem Sets 0 – 2 Week 3, Lab 3, and Problem Set 3 of CS50x 2023.
Problem Sets 0 – 3 Week 4, Lab 4, and Problem Set 4 of CS50x 2023.
Problem Sets 0 – 4 Week 5, Lab 5, and Problem Set 5 of CS50x 2023.
Problem Sets 0 – 5 Week 6, Lab 6, and Problem Set 6 of CS50x 2023
Problem Sets 0 – 6 Week 7, Lab 7, and Problem Set 7 of CS50x 2023.
Problem Sets 0 – 7 Week 8, Lab 8, and Problem Set 8 of CS50x 2023.
Problem Sets 0 – 8 Week 9, Lab 9, and Problem Set 9 of CS50x 2023.
Problem Sets 0 – 9 Week 10 and the Final Project of CS50x 2023.

When are deadlines?

CS50x does not have individual deadlines for assignments. You are welcome to work on and submit at your own pace.

The overall deadline for the course is end of day, UTC, on 31 December 2023 (Sunday, December 31, 2023, 11:59 PM UTC). For your convenience, we will often on this website render this time in your local timezone (2023-12-31T23:59:00+00:00).

If all required work is turned in before the above time, and ultimately receives a satisfactory grade (whether before or shortly after that deadline), you will be considered to have completed CS50x.

How will work I completed as part of CS50x 2022 carry forward into CS50x 2023?

Credit was given for work done in CS50x 2022 as follows. Note that you must have completed1 each row in a box in the left column before 1 January 2023 in order to have received credit for the corresponding problem set(s) and lab(s) in the right column. If you have only completed some of the items in a box in the left column, no credit will be given for that work. (The carryover is done on a per-week basis, not a per-problem basis.) Visit your CS50x Gradebook to see the weeks that have been credited, if any.

Completed1 in CS50x 2022 Credit equivalent in CS50x 2023
Scratch Problem Set 0
Mario (Less) OR Mario (More)
Cash OR Credit
Problem Set 1
Lab 1
Caesar OR Substitution
Lab 2
Problem Set 2
Lab 2
Runoff OR Tideman
Lab 3
Problem Set 3
Lab 3
Filter (Less) OR Filter (More)
Lab 4
Problem Set 4
Lab 4
Lab 5
Problem Set 5
Lab 5
Hello (Python)
Mario (Less) (Python) OR Mario (More) (Python)
Cash (Python) OR Credit (Python)
Readability (Python)
Lab 6
Problem Set 6
Lab 6
Lab 7
Problem Set 7
Lab 7
Lab 8
Problem Set 8
Lab 8
Lab 9
Problem Set 9
Lab 9
Final Project Final Project

1 By completed, we mean you earned a 70% or better on the problem before 1 January 2023.

Will work I completed for CS50x 2022 (or prior) carry forward into CS50x 2024?

Work completed in CS50x 2022 or prior is not subject to carry-forward for progress. Only work completed in CS50x 2023 will carry forward. This means if you received a credit for past work that carried forward into CS50x 2023, that credit will no longer be valid as of 1 January 2024, and you may need to redo (or at least resubmit!) some assignments. What this effectively means is that, depending on when in the calendar year you begin you have between 12 and 24 months to complete CS50x without needing to circle back and start resubmitting assignments. We know, particularly for folks who are trying to finish the course right at the end of December that this can prove difficult, but unfortunately we cannot make any exceptions to this rule for any reason. We therefore encourage you, if possible, to avoid trying to rush to complete the course at the deadline and instead spread your studies out over a reasonable stretch of time.

Will work I completed for CS50x 2023 carry forward into CS50x 2024?

Yes. We will announce exactly how that will happen in November or December 2023, but it is reasonable to assume that carryover will occur in a similar manner to how the 2022-to-2023 transition took place, as referenced above.


Is my child too young to take CS50x?

CS50x is perhaps best suited for ages 13 and up. Some of the software tools that the course uses require a minimum age of 13 to sign up. Therefore, younger students might need a hand from a parent in getting set up.


Does my gradebook only show if I scored high enough to pass a problem? How can I see my actual numeric grades?

You can click on the problem name to go to your submission, where the individual correctness (check50) and style (style50) raw scores will be shown.

Your overall problem score is weighted 75% for correctness and 25% for style. In order to receive the green tick indicating completion, your overall score must be 70% or higher. As an example, if your check50 score is 7/8 and your style score is 0.95, your overall score will be (7/8 * 0.75) + (0.95 * 0.25) = 89%.

If you did not pass a problem, you can hover over the red cross to see what your actual score was.

If my style score is not as expected, why might that be?

Your style grade will be based on the style50 results for every source code file in your submission. When you run submit50, be sure that your folder includes only those files that are necessary for the problem set. If you have any extra test files in there, those will be counted towards your grade. Remove the extra files from the folder and resubmit to get an updated Style score.

Why does edX think my grade is 0%?

CS50x doesn’t use edX’s built-in gradebook, so all students’ scores appear (in edX’s gradebook) as 0%, always. Not to worry, see cs50.me/cs50x for your actual results. (Note that if you have carryover credit, as described in a question above, you will not see the individual results for those weeks.)


Does CS50x have office hours?

Not regularly! Afraid CS50x is too large, but you can still ask questions in any of CS50’s communities!

Does CS50x have sections?

During Fall 2022, course staff did conduct small sections with some CS50x students as the lectures were being filmed. While the course is too large to hold live sections for current students, these pre-recorded sections will be available (once ready!) for students to supplement the other course materials.