Brian Yu

Head Teaching Fellow

Doug Lloyd


This course picks up where Harvard College’s CS50 leaves off, diving more deeply into the design and implementation of web apps with Python, JavaScript, and SQL using frameworks like Django, React, and Bootstrap. Topics include database design, scalability, security, and user experience. Through hands-on projects, students learn to write and use APIs, create interactive UIs, and leverage cloud services like GitHub and Heroku. By semester’s end, students emerge with knowledge and experience in principles, languages, and tools that empower them to design and deploy applications on the Internet.


CSCI E-50, CS50x, or prior experience in any programming language.


You are expected to

  • watch nine lectures,
  • attend seven sections,
  • complete eight quizzes,
  • implement five assigned projects, and
  • design and implement a final project.


Final grades are determined using the following weights:

Projects 0 through 4 55%
Final Project 20%
Quizzes 15%
Section attendance 10%

Scores are normalized across teaching fellows at term’s end, so mid-semester comparisons among students of scores are not reliable indicators of standing.

Projects (starting with Project 1) will be graded on the basis of correctness, design, and style, with each project’s overall score computed as 3 × correctness + 2 × design + 1 × style. The more-complex projects later in the course contribute more to your final grade than the earlier ones do.

  • Correctness refers to the extent to which your code is consistent with the project’s specifications and free of bugs.
  • Design refers to the extent to which your code is written well (i.e., efficiently, elegantly, and logically).
  • Style refers to the extent to which your code is readable (i.e., clear, consistent, commented, indented, with variables aptly named). This includes, but is not limited to, adherence to Python’s style guide, which you can verify using pycodestyle.

Project 0 will be graded along the axis of Correctness only.

Beyond what is stated here, the course does not provide further detail about grade conversions. The course does not offer mid-semester grade projections (except in cases where a student is clearly in jeopardy of an unsatisfactory grade), as each element’s weight, above, can materially alter that projection.


Lectures are watched on-demand.

  date topic
Lecture 0 2024-01-22T00:00:00-05:00 HTML and CSS
Lecture 1 2024-01-29T00:00:00-05:00 Git
Lecture 2 2024-01-29T00:00:00-05:00 Python
Lecture 3 2024-02-05T00:00:00-05:00 Django
Lecture 4 2024-02-19T00:00:00-05:00 SQL, Models, and Migrations
Lecture 5 2024-03-04T00:00:00-05:00 JavaScript
Lecture 6 2024-03-25T00:00:00-04:00 User Interfaces
Lecture 7 2024-04-08T00:00:00-04:00 Testing, CI/CD
Lecture 8 2024-04-22T00:00:00-04:00 Scalability and Security


Quizzes are short assignments associated with each lecture that allow you to apply each week’s concepts. Each quiz is open-book: you may use any and all non-human resources during a quiz, but the only humans to whom you may turn for help or from whom you may receive help are the course’s heads.

  released due
Quiz A 2024-01-22T00:00:00-05:00 2024-01-26T23:59:00-05:00
Quiz B 2024-01-29T00:00:00-05:00 2024-02-02T23:59:00-05:00
Quiz C 2024-02-05T00:00:00-05:00 2024-02-09T23:59:00-05:00
Quiz D 2024-02-19T00:00:00-05:00 2024-02-23T23:59:00-05:00
Quiz E 2024-03-04T00:00:00-05:00 2024-03-08T23:59:00-05:00
Quiz F 2024-03-25T00:00:00-04:00 2024-03-29T23:59:00-04:00
Quiz G 2024-04-08T00:00:00-04:00 2024-04-12T23:59:00-04:00
Quiz H 2024-04-22T00:00:00-04:00 2024-04-26T23:59:00-04:00


Lectures are supplemented by weekly sections led by the teaching fellows. A schedule will be posted on the course’s website. Sections are an opportunity to discuss the course’s material, ask questions, and explore related material. Students are required to attend at least one section per week, unless granted an exception in writing from either the instructors or head teaching fellow before the start of the term.

While recordings of one section per week will be made available within 72 hours, watching those recordings after the fact does not satisfy this requirement.

Office Hours

Office hours are opportunities for guidance and feedback from the staff on projects as well as for discussion of the course’s material more generally. A schedule will be posted on the course’s website.


  released due
Project 0 2024-01-22T00:00:00-05:00 2024-02-04T23:59:00-05:00
Project 1 2024-02-05T00:00:00-05:00 2024-02-18T23:59:00-05:00
Project 2 2024-02-19T00:00:00-05:00 2024-03-03T23:59:00-05:00
Project 3 2024-03-04T00:00:00-05:00 2024-03-24T23:59:00-04:00
Project 4 2024-03-25T00:00:00-04:00 2024-04-07T23:59:00-04:00
Final Project 2024-04-08T00:00:00-04:00 2024-05-10T23:59:00-04:001

1The final project has two intermediate milestones. This due date is for the final implementation only.

Lateness Policy

You have a semester-long allowance of 72 hours (divided into 1-minute segments) to submit or re-submit projects (not the final project, however) late. This allowance should be used carefully (if at all!), but can otherwise be allocated in any manner of your choosing, which means that you may:

  • Use the full 72 hours on one project; or
  • Use just over 14 hours on each project; or
  • Use 9 hours and 22 minutes on one project, 30 hours and 11 minutes on another, 54 minutes on a third, etc.

Once the 72-hour allowance has been exhausted, then from that point on the course will begin to impose a 0.1% deduction to your grade for a project for each minute it is turned in late. Therefore, once your allowance is exhausted, for example:

  • Any work turned in 10 minutes late will earn 99% of the points it would have earned had it been turned in on time (a 1.0% deduction).
  • Any work turned in 60 minutes late will earn 94% of the points it would have earned had it been turned in on time (a 6.0% deduction).
  • Any work turned in 1,000 minutes (16 hours, 40 minutes) late is effectively zeroed, as that would be a 100.0% deduction.

Furthermore, whether availing yourself of your semester-long allowance (partially or fully) or not, the absolute latest any single project may be turned in for credit is 72 hours from its original deadline. Gradescope will not allow any submissions after that point, nor will the course ordinarily accept them via some other means.

Late work will not be accepted for the final project.

Questions about this policy should be directed to the head teaching fellow.

Extension Policy

Given the flexibility of the lateness policy, above, the course does not allow for extensions of any kind on its projects. Exceptions to this policy will be considered only in situations of documented medical or family emergency. Extensions that are only requested after a project’s deadline will not be considered at all. In these situations, communication with the course staff is paramount. The course rarely grants extensions retroactively, and so it is imperative you be in touch about your need for an extension promptly. The only individual authorized to grant extensions is the head teaching fellow; please be sure to include any relevant documentation in your request.


The Accessibility Services Office (ASO) is available to support all students who require accommodations due to disabling conditions; all such accommodations must be approved and coordinated by the ASO. If you require accommodations, please contact the ASO at 617-998-9640, or by email at

Academic Honesty

This course’s philosophy on academic honesty is best stated as “be reasonable.” The course recognizes that interactions with classmates and others can facilitate mastery of the course’s material. However, there remains a line between enlisting the help of another and submitting the work of another. This policy characterizes both sides of that line.

The essence of all work that you submit to this course must be your own. Collaboration on assigned projects is not permitted except to the extent that you may ask classmates and others for help so long as that help does not reduce to another doing your work for you. Generally speaking, when asking for help, you may show your code to others, but you may not view theirs, so long as you and they respect this policy’s other constraints. Collaboration on the course’s final project is permitted to the extent prescribed by its specification.

Below are rules of thumb that (inexhaustively) characterize acts that the course considers reasonable and not reasonable. If in doubt as to whether some act is reasonable, do not commit it until you solicit and receive approval in writing from the course’s heads. Acts considered not reasonable by the course are handled harshly. If the course refers some matter for disciplinary action and the outcome is punitive, the course reserves the right to impose local sanctions on top of that outcome that may include an unsatisfactory or failing grade for work submitted or for the course itself. The course ordinarily recommends exclusion (i.e., required withdrawal) from the course itself.

Regret clause. If you commit some act that is not reasonable but bring it to the attention of the course’s heads within 72 hours, the course may impose local sanctions that may include an unsatisfactory or failing grade for work submitted, but the course will not refer the matter for further disciplinary action except in cases of repeated acts.


  • Communicating with classmates about assignments in English (or some other spoken language), and properly citing those discussions.
  • Discussing the course’s material with others in order to understand it better.
  • Helping a classmate identify a bug in their code at office hours, elsewhere, or even online, as by viewing, compiling, or running their code after you have submitted that portion of the assignment yourself, provided that you add a citation to your own code of the help you provided and resubmit yourself.
  • Incorporating a few lines of code that you find online or elsewhere into your own code, provided that those lines are not themselves solutions to assigned problems and that you cite the lines’ origins.
  • Sending or showing code that you’ve written to someone, possibly a classmate, so that he or she might help you identify and fix a bug, provided you properly cite the help.
  • Submitting the same or similar work to this course that you have submitted previously to this course, CS50 AP, or CS50x.
  • Turning to the course’s heads for help or receiving help from the course’s heads during quizzes.
  • Turning to the web or elsewhere for instruction beyond the course’s own, for references, and for solutions to technical difficulties, but not for outright solutions to assignments.
  • Using CS50’s own AI-based software (including, ddb, et al.), but not presenting its answers as your own.
  • Whiteboarding solutions to assignments with others using diagrams or pseudocode but not actual code.
  • Working with (and even paying) a tutor to help you with the course, provided the tutor does not do your work for you.

Not Reasonable

  • Accessing a solution to some assignment prior to its deadline.
  • Accessing or attempting to access, without permission, an account not your own.
  • Asking a classmate to see their solution to an assignment before its deadline.
  • Discovering but failing to disclose to the course’s heads bugs in the course’s software that affect scores.
  • Decompiling, deobfuscating, or disassembling the staff’s solutions to assignments.
  • Failing to cite (as with comments) the origins of code or techniques that you discover outside of the course’s own lessons and integrate into your own work, even while respecting this policy’s other constraints.
  • Giving or showing to a classmate a solution to an assignment when it is he or she, and not you, who is struggling to solve it.
  • Looking at another individual’s work during the quizzes or exam.
  • Manipulating or attempting to manipulate scores artificially, as by exploiting bugs or formulas in the course’s software.
  • Paying or offering to pay an individual for work that you may submit as (part of) your own.
  • Providing or making available solutions to assignments to individuals who might take this course in the future.
  • Searching for or soliciting outright solutions to assignments online or elsewhere.
  • Splitting an assignment’s workload with another individual and combining your work.
  • Submitting (after possibly modifying) the work of another individual beyond the few lines allowed herein.
  • Submitting the same or similar work to this course that you have submitted or will submit to another.
  • Submitting work to this course that you intend to use outside of the course (e.g., for a job) without prior approval from the course’s heads.
  • Turning to humans (besides the course’s heads) for help or receiving help from humans (besides the course’s heads) during the quizzes.
  • Using third-party AI-based software (including ChatGPT, GitHub Copilot, the new Bing, et al.) that suggests answers or lines of code.
  • Viewing another’s answer to a question and basing your own answer on it.

Acknowledgement and Authorization

Harvard plans to record audio, photos, and video of Computer Science 50 (CS50) lectures, sections, office hours, seminars, and other events and activities related to CS50 (the “Recordings”), with the aims of making the content of the course more widely available and contributing to public understanding of innovative learning (the “Projects”). As part of the Projects, the Recordings, or edited versions of them, may be made available to other Harvard students, to students at other educational institutions, and to the broader public via edX, the Internet, television, theatrical distribution, digital media, or other means. One of the ways it is expected that the Recordings, or edited versions of them, will be made publicly available is under a Creative Commons Attribution-NonCommercial-ShareAlike (CC BY-NC-SA) license. Another example is that Harvard may make and disseminate montages of “memories” from the class with images from the Recordings. The Recordings also may be used to make other derivative works in the future. Students may elect not to appear in photos and video used in the Projects and may still participate fully in CS50.

To attend CS50, you will need to sign online an Acknowledgement and Authorization in the following form:

I understand and agree that, if I do not wish any photos or video of me to be used as part of the Projects:

  • If I am participating in CS50 in a classroom or other course location, I should sit in the designated “no-film” zone of the classroom or location, and should not walk in the field of view of the cameras.
  • If I am participating in CS50 online, I should turn off my own camera and should not display a photo of myself. In addition, if I do not wish my real name to be displayed when I speak and my voice is recorded, I should select a pseudonymous user name in Zoom (or other online service). If I select a pseudonymous user name, I will inform the instructor, so the instructor knows who I am.

I understand that I am free not to be included in the Projects’ photos and video in this way, and that this will not affect my grade or my ability to participate in course activities.

Unless I exclude myself from the Projects’ photos and video as described above and take any other steps outlined by the instructor to avoid being filmed, I authorize Harvard and its designees to make and use Recordings of my participation in CS50 and activities related to CS50. I understand and agree that the Recordings may include my image, name, and voice. I also understand and agree that, even if I opt out of the Projects’ photos and video and choose a pseudonymous user name, my voice will be recorded if I am participating online, and may be picked up by microphones outside the “no-film” zone if I am in a CS50 classroom or other location, and my spoken name also may be included in the Recordings. If the class is online, I may participate instead via chat messages, which will not be included in the Recordings.

I understand and agree that Harvard and its designees will have the irrevocable, worldwide right to make, edit, modify, copy, publish, transmit, distribute, sell, publicly display, publicly perform, and otherwise use and make available the Recordings and any other works that may be derived from those Recordings, in any manner or medium now known or later invented, in connection with the Projects, and to authorize others to do so as well. I hereby transfer to Harvard any rights, including copyrights, I may have in the Recordings that Harvard makes. I will remain free to use and disseminate any ideas, remarks, or other material that I may contribute to course discussions.

I acknowledge and agree that I will not be entitled to any payment, now or in the future, in connection with the Recordings or any works derived from them. This Acknowledgment and Authorization is a binding agreement, and is signed as a document under seal governed by the laws of the Commonwealth of Massachusetts.

Unless you exclude yourself as described in the Acknowledgment and Authorization, you are agreeing, by attending CS50, that your participation in CS50 and related activities may be recorded and used by Harvard in connection with the Projects without further obligation or liability to you, even if you do not sign any authorization.

If you have any questions about the above, contact