CodeHS Help for Students: Errors, Resets and Debugging

In short

Most CodeHS problems have documented fixes. A frozen Check Code button usually means an infinite loop. To start an exercise over, open More, then History, choose Reset Code and press Save. In unit-test exercises, write and run your function in the Scratchpad, and make it return a value. For login trouble, use your school email or your class’s Google, Clever or Canvas sign-in. Modern Age Coders teaches this live online for US students, in a batch or one to one, and the first class is free.

Learn it with a teacher

Three courses for students who meet CodeHS at school

Live lessons that teach the ideas behind the exercises, so the CodeHS work makes sense.

COX / 01

AP Computer Science A

Java for the AP exam, unit by unit, alongside your school course.

Open the syllabus →

COX / 02

AP Computer Science Principles

The big ideas, the exam and planning a Create task of your own.

Open the syllabus →

COX / 03

Python for teens

Ages 13 to 18. Functions, loops and testing, from first principles.

Open the syllabus →

Find your problem

What is going wrong, and where CodeHS explains the fix

Each row is a problem CodeHS documents in its help center, with the fix it gives. Start with the row that matches your screen.

Common CodeHS problems and the documented fixes, from help.codehs.com (read 17 October 2026)
What you see	What CodeHS says it usually means	What to try
The browser freezes or crashes after Run or Check Code	The code contains an infinite loop	Comment out loops one at a time to find it, then make sure its condition can become false
The Check Code button does nothing	An error in your code, or an infinite loop	Run the program first and read any error message
You want to start an exercise again	Reset Code restores the starter code	More, then History, then Reset Code, then Save
A unit test freezes after Check Code	User input inside a unit-test function, or no return value	Remove input the instructions did not ask for; make the function return
A Karel exercise fails on style	The general Karel autograder checks syntax, indentation and naming	Read the exact Style message; it names the line or function
Your HTML page shows No CodeHS.me Site Here	The program was blocked, or a link does not match a filename	Check whether your links and filenames match exactly
The cursor is misaligned on a Chromebook	The browser font is not monospace	Set Chrome’s fixed-width font to one with Mono in its name
A lesson video will not play	The video host is blocked on the school network	Use the CodeHS-hosted version of the video, or the lesson slides

Reset Code, carefully

CodeHS says Reset Code is available for both teachers and students, and that after clicking it you must save the change with the Save button. It returns the exercise to its starter code, so anything you wrote is replaced.

Before resetting, look through the History tab. CodeHS describes it as a list of every previous version of your program, which often lets you recover the last version that worked instead of starting from nothing.

Ask your teacher inside CodeHS

CodeHS has a built-in way to message your teacher about a specific exercise: open the More tab in the code editor and choose Conversation. Replies appear in your Inbox, under the bell icon.

Asking there, with the exercise open, is usually faster than an email, because your teacher can see the exact code you mean.

Sources: CodeHS help center articles on code that crashes the browser, resetting your code and sending questions to your teacher, read 17 October 2026. We are not connected with CodeHS.

Debugging tools

The debugging tools already inside the CodeHS editor

CodeHS lists five tools for students in its debugging article, plus a separate step debugger for some program types. Most students use one or two of them. All of them help.

CodeHS editor tools for finding bugs, from the CodeHS help center (read 17 October 2026)
Tool	Where it is	What it is good for
Docs tab	In the code editor	Examples and syntax of the concepts your course has covered so far
History tab	Under More	Every earlier version of your program, to see what changed since it last worked
Speed slider	In the editor	Running code slowly to see where it goes off track
Next and Last buttons	Top of the editor	Running one line at a time to find the exact line at fault
Test Code button	Red button in the editor	Seeing which autograder tests pass; a progress bar counts them
Step debugger	Gear icon, then Debug Mode	Pausing a Python 3, Python 3 Graphics (tkinter) or Java (main) program and stepping through it

The loop that freezes the page, and its fixpython

# ours: why the Run button seems dead
count = 0
while count < 3:
    print("checking", count)
    # count never changes, so count < 3 stays true

# the fix: change the variable the condition tests
count = 0
while count < 3:
    print("checking", count)
    count += 1
print("done")

Ours, run with Python 3.13.6 outside CodeHS. The first loop printed checking 0 without end until we stopped it; the second printed checking 0, 1 and 2, then done. CodeHS’s own questions apply: in a while loop, will the condition ever become false?

The step debugger, in five buttons

CodeHS describes five debugger functions: Run, which runs normally; Step, which moves to the next command even inside another file or library; Next, which moves to the next command in the current file; Continue, which runs until the end or a crash; and Stop.

Most students only need Next. Press it, watch which line lights up, and check whether the variables hold what you expected at that moment.

Commenting out, the low-tech tool

CodeHS recommends commenting out sections and re-running, so the skipped code tells you by elimination where an error lives. For infinite loops, it suggests testing sections with for or while loops first, then if and else statements, then the rest.

It is a slow method, but it never fails, and it works in every language and every editor you will ever use.

Sources: CodeHS help center, tips on debugging code and using the step debugger, read 17 October 2026.

Unit tests and the Scratchpad

Why a unit test fails when your code looks right

Many CodeHS exercises in Python, JavaScript and Java are graded by unit tests. CodeHS explains how they differ from a normal program, and the difference trips up a lot of students.

The two files in a CodeHS unit-test exercise, from the CodeHS help center (read 17 October 2026)
	Unit Test file	Scratchpad file
Graded?	Yes	No
Can you Run it and print?	No: it can not Run or print to the console	Yes: it can Run and print to the console
What belongs in it	A fully working function that works as expected	Experiments: different inputs, print statements, mistakes
What CodeHS requires	A Unit Test requires a return statement and does not ask for user input	Anything that helps you test the function

A function that prints instead of returningpython

# Scratchpad (ours): prints the answer, returns nothing
def add_tax(price):
    print(price * 1.08)

result = add_tax(50)
print("result is", result)

# output
54.0
result is None

Ours, a made-up example, not a CodeHS exercise. It looks right because 54.0 appears on screen, but the function hands nothing back, so result is None. A unit test checks what the function returns, and would see None.

The same function, returning its valuepython

# Scratchpad (ours): returns the answer instead
def add_tax(price):
    return round(price * 1.08, 2)

print(add_tax(50))
print(add_tax(0))
print(add_tax(19.99))

# output
54.0
0.0
21.59

Ours, run with Python 3.13.6. CodeHS suggests testing edge cases such as zero and negative inputs in the Scratchpad; we add a value that is not a round number, like 19.99, then copy the working function into the Unit Test file.

The CodeHS routine, step by step

CodeHS gives four steps: copy the starter code from the Unit Test into the Scratchpad; write and test your function in the Scratchpad, where you can run it; copy the working function back into the Unit Test file; and when it passes all the checks, submit it.

If the program will not run, CodeHS points out that the green Run button only runs the Scratchpad, not the Unit Test file, and that you need to both define and call the function to see anything.

Why the test does not show you the answer

Students sometimes ask why CodeHS will not just show what the test expected. The test is there to check your function, and the exercise is there to teach you to write it. That is the same reason we teach the idea of returning a value rather than supplying the function.

A good question to ask yourself instead: if someone called my function with a value I did not try, what would it give back?

Source: CodeHS help center, using the Scratchpad and Unit Test files, read 17 October 2026.

Karel autograder messages

What the Karel autograder is telling you

Karel exercises use a general autograder that applies a set of tests to each program, from the final world to the way functions are named. CodeHS publishes the common messages. Here is what each one asks you to check.

Common Karel autograder messages, quoted from the CodeHS help center (read 17 October 2026)
Message	What it checks	What to look at
Functionality: World _______	Karel’s location, ball count and square colors at the end, against each Result World	Run it and compare your final world with the expected one
Style: You are missing a semicolon on the following lines:	That every command ends with a semicolon	The line numbers listed
Style: It looks like your indentation is off on line ___	Indentation	Code inside a function or loop should be indented one level
Style: Some of your functions (FunctionName) do not start with a lowercase letter.	Function naming	Names like turnRight, not TurnRight
Style: You have a function function1 nested inside another function function2.	Functions defined inside other functions	Define functions one after the other
Style: You should not redefine turnRight()/turnAround() because SuperKarel already knows it.	Unneeded definitions in SuperKarel and UltraKarel	Delete your own turnRight or turnAround

Functionality first, then style

A program can make Karel finish in the right place and still fail on style, and the other way round. Fix the Functionality test first, because changing what the program does may change which style messages appear.

Then work through the Style messages in order. Each one quotes the exact name or line, so there is no guessing involved.

Why style is graded at all

Naming functions in lowercase camelCase and indenting consistently are conventions every programmer follows, because code is read far more often than it is written. Karel is where CodeHS starts teaching that habit.

Students who build it early find their later Java and Python code much easier to debug, because they can see the structure at a glance.

Source: CodeHS help center, Karel autograder messages, read 17 October 2026.

Login, devices and versions

Login trouble, Chromebooks and which version of Java or Python you are on

Some CodeHS problems have nothing to do with code. These are the ones CodeHS documents for signing in, school devices and language versions.

Check the email address. CodeHS’s first tip is to make sure you are using your school-issued email, not a personal one.
Use your class’s sign-in route. If your class uses Google Classroom, use Log in with Google; if it uses Clever or Canvas, launch CodeHS from there instead of typing a password.
Wrong Google account? Chrome may sign you in automatically with another account. Sign out at myaccount.google.com, or open an incognito window with Control + Shift + N on Windows or Command + Shift + N on a Mac (some schools disable incognito).
Still locked out? Use Forgot Password, or ask your teacher, who can update your password.
Cursor not lining up with your text on a Chromebook? In Chrome settings, under Appearance and Customize fonts, choose a fixed-width font with Mono in its name, and check the browser language is English (United States).
Not sure which language version you are on? In any exercise or Sandbox program, open More, then About.

Language versions on CodeHS, from the CodeHS help center (read 17 October 2026)
Language	What CodeHS says
Python	Python 3.8, 3.11 and 3.12 are provided; Python 3, Python 3 Graphics (tkinter) and Pygame programs use 3.11
Java	Most core courses currently use Java 8 (1.8); Java 21.05 is used in AP Computer Science A (Cortado), all new courses and all new Sandbox programs
JavaScript	ES6, the version all browsers use
Java, interactive	JShell, a Java read-eval-print loop, is supported

Versions matter when code from a textbook, a website or a home computer behaves differently on CodeHS. A newer Java feature will not compile in a course still on Java 8. Sources: CodeHS help center, login troubleshooting, Chromebook cursor fixes and language versions, read 17 October 2026.

About answers

Why we do not give CodeHS answers, and what helps instead

Search for CodeHS and the suggestions fill up with answer keys for every unit. We understand why: it is late, the test will not pass, and the deadline is tomorrow. Here is why we will not supply them, and what we do instead.

The work is graded

CodeHS exercises are graded by your teacher and the autograder. Copying an answer means handing in work that is not yours, and we will not take part in that.

Schools set rules for this

CodeHS gives teachers settings such as copy and paste prevention, which in CodeHS Pro stops students in a section from pasting into the editor. Schools take this seriously.

The next unit needs this one

CodeHS courses build step by step. An answer copied in unit 3 leaves a gap that the unit 5 exercise will find, usually at a worse moment.

What a lesson with us looks like instead

The student shares their screen with the CodeHS exercise open. The teacher asks what the exercise wants, what the code does now, and what the autograder message says, and then teaches the idea that is missing, using a different example of our own.

The student then goes back to their exercise and writes the code themselves. It takes longer than copying, and it is the only version that helps on the next exercise and on the test.

AP students on CodeHS

CodeHS says its AP Computer Science A course (Cortado) runs Java 21.05. The AP exam itself is, in College Board’s words, a fully digital exam taken in the Bluebook app, so CodeHS is where you practice, not where you sit the test.

For exam-focused help alongside your school course, see our AP Computer Science A classes or AP CSP coaching.

Sources: CodeHS help center, copy and paste prevention; College Board, AP Computer Science A Exam. Both read 17 October 2026. AP is a trademark of College Board, which is not connected with us.

Getting unstuck

Four stages of a CodeHS student

Where students usually are when they first search for CodeHS help, and where they can get to.

Stages of working through CodeHS (ours)
Stage	What it looks like
1. Stuck	Presses Check Code again and again, hoping for a different result
2. Reading	Reads the autograder and error messages and goes to the line they name
3. Testing	Uses the Scratchpad, the History tab and the debugger to check ideas
4. Independent	Finishes exercises without help and can explain how the code works

For parents

A child who is stuck on CodeHS at 10 pm needs to understand one idea, not to be given one answer.

Asking them to read the autograder message aloud is a surprisingly good first step, even if you do not code.

For students

Run before you check. The Run output often shows the problem the autograder is hinting at.

Use History before Reset. Your last working version is usually still there.

The catalogue

Nine courses that match what CodeHS students learn at school

Live teaching with a regular teacher, as a batch or one to one, in the same languages CodeHS uses.

I

AP and exam courses

High school

COX / AP / 01

AP Computer Science A

The Java AP course, live.

Open the syllabus

COX / AP / 02

AP Computer Science Principles

Exam topics and the Create task process.

Open the syllabus

COX / AP / 03

Java for teens

Java before or beside AP CSA.

Open the syllabus

II

Languages CodeHS teaches

Teens

COX / LANG / 01

Python for teens

Functions, lists and testing.

Open the syllabus

COX / LANG / 02

JavaScript for teens

Interactive pages and browser games.

Open the syllabus

COX / LANG / 03

HTML and CSS

The web design units, in depth.

Open the syllabus

III

Younger coders

Ages 6 to 12

COX / KID / 01

Scratch coding

Events and loops in blocks.

Open the syllabus

COX / KID / 02

Python for kids

Typed code with turtle art and games.

Open the syllabus

COX / KID / 03

Coding for kids

From blocks to first real apps.

Open the syllabus

How lessons run

Live help that fits around the school day

Weekdays or weekends, flexible: choose your batch, or for a very personalised plan choose 1-on-1 at your convenience, weekend mornings or weekdays.

Weekdays

Late afternoons and evenings in US time zones.

Weekends

A weekly slot away from the school rush.

1-on-1

Booked around unit tests and deadlines.

One teacher

The same teacher, week after week.

CodeHS on screen

Share the exercise; we teach the idea.

Our own examples

Different problems that teach the same concept.

No answer keys

Your CodeHS work stays yours.

All fifty states

Live and online, wherever you are.

Batch or one to one

Fifteen to twenty students, or one.

Student work

Things our students have built

Projects from students who once worked through the same exercises. Browse more on the student labs page.

AI and ML

NutriLife

An AI nutrition coach that reads what you eat and works you toward a target.

by Bhavya · Open it

AI and ML

Misti

A chatbot that answers mathematics and programming questions, built and deployed by a student.

by Harshit · Open it

AI and ML

GuardianX

An assistant that helps a young person recognise unsafe situations online.

by Vivaan · Open it

Web app

SkyCast

A weather forecasting site with live conditions for any location.

by Krish

Fees

CodeHS is provided by your school; our classes are separate. You pay for live teaching one month at a time, in US dollars, with nothing to sign for the semester and no cost for stopping at the end of any month.

Free first class

USD 0

no card required

A free first lesson
Bring the exercise you are stuck on
No card needed

Book it

Group batch

USD 100

a month, billed in US dollars

Fifteen to twenty learners
A regular teacher
Choose your batch
Monthly payment

Start here

One to one

USD 150

a month, billed in US dollars

A private teacher
At times that suit you
Built around your school course

Enquire

What families say

Rated 4.9 across 547 Google reviews

Word-for-word reviews that families posted on Google.

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"The one step solution for my son. Modern Age Coders make learning coding so simple that kids love it. The teachers explain complex concepts clearly with practical exercises and interactive content."

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Parent

★★★★★

"Modern Age Coders has been a game-changer for me. I struggled to grasp IT concepts and coding before joining, but their classes transformed everything. I can now confidently write complex programs with ease."

Samriddha Mondal

Student

★★★★★

"One of the most wonderful education centres out there. Education is not limited to school syllabus but focuses on skill development."

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Student

★★★★★

"My child Dhairya is really enjoying the Modern Age Coders classes. This is his first online class and he eagerly looks forward to it. I can already see his improvement, and the teachers are very cooperative."

Sonam Oswal

Parent of Dhairya

★★★★★

"Modern Age Coders have wonderful teachers who teach in a clear, easy and practical way. The teacher boosts students' confidence and inspires them to learn without hesitation."

Sonu Goyal

Parent

★★★★★

"I highly recommend this computer coding class! The teachers are incredibly knowledgeable and passionate about coding."

Ritu Kedia

Parent

Questions from students and parents

CodeHS help: common questions

Why is my CodeHS not working?

CodeHS says that if the browser freezes or the Check Code button stops responding, the code may contain an error or an infinite loop. Run the program first, read any message, and check that every loop has a condition that can become false.

How do I reset a CodeHS assignment?

Open More, then History, in the editor and click Reset Code, which restores the starter code. CodeHS says to save afterwards with the Save button. Look through History first, because an earlier working version may still be there.

Why does my CodeHS unit test fail when my code prints the right answer?

A unit test checks what your function returns, not what it prints. CodeHS says a unit test requires a return statement and does not ask for user input. Test the function in the Scratchpad, then copy it back.

What is the CodeHS Scratchpad for?

It is an ungraded file in unit-test exercises where you can run code, print and try different inputs. The Unit Test file is the graded one and cannot be run or print to the console.

What does You are missing a semicolon mean in Karel?

It is a Karel autograder style message. CodeHS says the test checks that every command ends with a semicolon, and the message lists the lines where one is missing.

How do I use the CodeHS debugger?

Click the gear icon in the editor and turn on Debug Mode. CodeHS says the step debugger works for Python 3, Python 3 Graphics (tkinter) and Java programs with a main method, with Run, Step, Next, Continue and Stop.

I cannot log in to CodeHS. What should I do?

Use your school-issued email, not a personal one. If your class uses Google, Clever or Canvas, sign in through that. You can also use Forgot Password, or ask your teacher, who can update your password.

Which version of Java does CodeHS use?

CodeHS says most core courses use Java 8, while its AP Computer Science A course (Cortado), all new courses and new Sandbox programs use Java 21.05. You can check any exercise under More, then About.

Can you give me the CodeHS answers?

No. We do not provide CodeHS answers, answer keys or solutions to any graded assignment. We teach the concept with our own examples so you can solve the exercise yourself and explain your code.

When are your live classes for US students?

Weekdays or weekends, flexible. Choose your batch, or for a very personalised plan choose 1-on-1 at your convenience, weekend mornings or weekdays.

How much do the classes cost?

The first lesson is free. After that, classes are paid one month at a time, and the fees section of this page shows the amount in US dollars.

Elsewhere on this site

Related pages

More for US students who code at school.

Coding classes in the USA

Every page we have for US families.

How to debug code

A step-by-step method for any bug.

AP Computer Science A classes

Live AP CSA preparation.

AP CSP coaching

Live AP CSP preparation.

AP CSP or AP CSA first?

Choosing an order for the two courses.

Python for beginners

The basics behind the Python units.

Code.org App Lab help

App Lab help: events, variables, screens, sound and data, from the official docs.

Java cannot find symbol error

Java cannot find symbol, decoded: real javac output, eight causes, numbered fixes.

BlueJ not working: fixes

BlueJ not working? Official fixes for install, VM errors, output and frozen runs.

Start here

Book a free first lesson

Tell us which CodeHS course you are taking and which idea keeps tripping you up. The teacher plans the first lesson around that concept, with examples of our own.

If you would like to see a lesson first, how we teach walks through one; the courses page lists every syllabus.

WhatsApp us · +91 91233 66161 · connect@modernagecoders.com

We teach live over video, and our teachers are based in India, so there is no local branch to visit. WhatsApp is the fastest way for a US family to reach us.

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A priority demo is a full class of about 45 to 60 minutes. After the class the mentor sends a written skill report and a personal learning roadmap on WhatsApp. If you enrol, the demo fee is adjusted against your first month's fee. Share your demo Order ID with us on WhatsApp and we take it off.

Book a priority demo

Three courses for students who meet CodeHS at school

AP Computer Science A

AP Computer Science Principles

Python for teens

What is going wrong, and where CodeHS explains the fix

Reset Code, carefully

Ask your teacher inside CodeHS

The debugging tools already inside the CodeHS editor

The step debugger, in five buttons

Commenting out, the low-tech tool

Why a unit test fails when your code looks right

The CodeHS routine, step by step

Why the test does not show you the answer

What the Karel autograder is telling you

Functionality first, then style

Why style is graded at all

Login trouble, Chromebooks and which version of Java or Python you are on

Why we do not give CodeHS answers, and what helps instead

The work is graded

Schools set rules for this

The next unit needs this one

What a lesson with us looks like instead

AP students on CodeHS

Four stages of a CodeHS student

For parents

For students

Nine courses that match what CodeHS students learn at school

AP and exam courses

AP Computer Science A

AP Computer Science Principles

Java for teens

Languages CodeHS teaches

Python for teens

JavaScript for teens

HTML and CSS

Younger coders

Scratch coding

Python for kids

Coding for kids

Live help that fits around the school day

One teacher

CodeHS on screen

Our own examples

No answer keys

All fifty states

Batch or one to one

Things our students have built

NutriLife

Misti

GuardianX

SkyCast

Fees

Rated 4.9 across 547 Google reviews

CodeHS help: common questions

Why is my CodeHS not working?

How do I reset a CodeHS assignment?

Why does my CodeHS unit test fail when my code prints the right answer?

What is the CodeHS Scratchpad for?

What does You are missing a semicolon mean in Karel?

How do I use the CodeHS debugger?

I cannot log in to CodeHS. What should I do?

Which version of Java does CodeHS use?

Can you give me the CodeHS answers?

When are your live classes for US students?

How much do the classes cost?

Related pages

Book a free first lesson

Want a class sooner? Book a priority demo

Keep exploring Modern Age Coders

Related courses and guides

Free resources

From the blog

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