Debugging In Scratch: How To Fix Your Code Fast

Debugging Scratch code can be frustrating, especially when your child is stuck and unsure what went wrong. But don’t worry—there are simple strategies that can make fixing bugs easier and even fun! This helpful guide will give you the tools to confidently guide your child through troubleshooting their code. First we'll review debugging strategies you can use on any project, and then we'll get into some specific solutions to the some of the most common Scratch issues kids run into. From saving copies of projects to testing one change at a time, discover practical advice that will help your child keep creating!

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How To Fix Your Scratch Code: Debugging Tips And Tricks To Help Your Child

Discover a range of simple, effective techniques that you and your child can use to identify and fix common coding issues. From making a backup copy before you start editing your code to attempt fixing it, to testing one change at a time, these tips will help you troubleshoot to make sure your child’s Scratch project runs the way they hoped.

1. Save A Copy First

When you’re trying to fix a bug in your Scratch project, it’s a great idea to make a copy of your code first before you start tinkering with it. That way, if something goes wrong or you accidentally make things more complicated, you’ll have your original version to go back to!

Save a copy of the Scratch program file to your computer (File > Save to your computer). It can be uploaded to Scratch anytime you want to see it. Give it a name to help you remember which copy it is, such as the version number or date along with the project name.

2. Test One Change at a Time

When debugging, it can be tempting to change a bunch of things at once, but that can make it hard to know which change actually fixed the problem—or if it made things worse! Instead, make just one change at a time and test it before moving on to the next thing.

Here’s how you can do it:

• Try adjusting one block, then click the green flag to see if it fixed the bug.
• If the bug is still there, try something else, but again, just one thing at a time.

3. Break Long Sequences Into Smaller Pieces

When you’re building your Scratch project, it’s a good idea to code in small steps: write a little bit of code, then test it out to see if it works the way you want. By doing this, if something goes wrong, it’s easier to find where the problem started because it’s likely in the last bit of code you added.

If your code is already written and there’s a bug, you can still use this method! Just break down your long sequence of code into smaller pieces. Separate a few blocks and click them one at a time to see what each one does. You can even try breaking your code into smaller groups of two to four blocks and test each group to find where the bug might be hiding.

Click on a single block or a small group of blocks in your code area to run just that part. Once you know it works, add it back to your main program, and then test the next piece.

4. Play With Your Block Order

Sometimes, the order of your blocks can make a big difference in how your Scratch project works! Try switching around the order of your blocks and see what happens. Ask yourself:

• What needs to happen first?
• What needs to happen second?
• Does anything need to reset before the next part runs?

5. Read Aloud or Explain the Code Step-by-Step

Have you ever read something you wrote out loud and noticed a mistake you didn’t see before? You can do the same thing with your code. Read your Scratch code aloud, one step at a time, or explain it to someone else—maybe a friend, a parent, or even your pet! As you go through your code, pretend you’re the computer.

Think about each step:

• Are you telling the computer exactly what to do?
• Are there any steps missing?
• Does everything reset properly when you want to start over?

6. Check Your Values

When you’re using variables in your Scratch project—like custom variables or ones that show things like x position, direction, or the answer—it’s important to know what their value is while your code is running. If something isn’t working as expected, you might need to check the value to see what’s going on.

Here are a few ways you can find out the value:

• If there’s a checkbox next to the variable or reporter block in the block palette, check it off to show the value on the stage. You can uncheck it when you're done debugging.
• You can place the variable inside a "say" block to have your sprite tell you the value. If you put this in a forever loop, it will keep updating the value as it changes.
• You can also click on the variable in the block palette or script area to get a one-time report of its current value.

Think about these questions: Should all the sprites control this variable, or just one? Where is the value being reset? Where is it being changed?

Debugging Tips For Common Scratch Coding Problems

Let's take a look at some of the most common issues kids run into with Scratch coding, and a few ways to debug them so you can guide your child through fixing their code.

1. What to do when your Sprite is not moving

Problem: My sprite doesn’t move when using a motion block such as move 10 steps.

Fix:

• Ensure the movement block is placed inside a control block like when green flag clicked or when <blank> key pressed.
• Check the direction the sprite is facing. Use the point in direction block to correct the direction.

2. What to do if your sprite disappears or stops when gets to the edge of the Stage

Problem: My sprite goes off the screen and disappears.

Fix:

• Add an if on edge, bounce block to keep the sprite on the screen.
• Use the go to x: [] y [] block to reset the sprite’s position.

3. What to do if your sound isn't playing

Problem: The sounds I want are not being triggered.

Fix:

• Be sure you added a block to play sound when the sprite is clicked. If you have copied code from another sprite, you will need to add the sound to this sprite in the Sounds tab.
• Ensure the sound block (play sound until done) is connected to a control block like when [] clicked.

4. Your broadcast doesn't work

Problem: Messages sent via broadcast [message] don’t trigger the desired action.

Fix:

• Verify that the broadcast block sends the correct message.
• Check if the corresponding when I receive [message] block is properly set up.

5. Your sprite doesn't respond to key presses

Problem: Pressing keys has no impact on the sprite but I want it to.

Fix:

• Make sure the when [key] pressed block is used.
• Ensure the correct key is selected in the block’s dropdown menu.

6. Your clones don't work the way you want them to

Problem: My clones are not appearing or behaving incorrectly.

Fix:

• Use the create clone of [myself] block correctly. This block creates an identical version of your selected sprite each time you click on it. To see your clone, drag it away from the original.
• Make sure the when I start as a clone block is properly configured with the actions the clone should perform. When a clone is created, it starts running the code attached to this block.
• If needed, use the delete this clone block to manage the number of clones. This block deletes the clone it’s running and stops all of its scripts. Use this block if you want your sprite to disappear, like bubbles and magic tricks, for example.

7. Your variables aren't updating - fixing the score

Problem: Variables like score or lives are not updating when expected.

Fix:

• Ensure the set [variable] to [] or change [variable] by [] block is used where appropriate.
• To check the value of the variable you can drag a reporter block onto the programming canvas and click on it. The current value of the variable is displayed.
• Double check that the variable is being updated in the correct section of code.

A typical use of a variable is to be used in a loop as a counter. In that case we use the variable score. A counter loop consists of these blocks:

• set score to the initial value (often 1)
• enter a repeat loop
• do something with variable score
• change score by an increment (often 1)

For example, this code makes your sprite say the score from 1 to 10.

8. Your costume or backdrop don't change

Problem: My sprite or stage does not switch costumes or backdrops as expected.

Fix:

• Use the switch costume to [] or switch backdrop to [] blocks.
• Select your two backdrops or costumes, then click on the image of the backdrop below the Stage (on the left of your screen) to code your backdrop. You will see all selected backdrops to the left of your screen in the backdrops Paint Editor.
• Ensure the costume or backdrop is named correctly and matches the selection in the block.

9. Issues with infinite loops

Problem: My project seems to freeze or my sprite behaves erratically due to an infinite loop.

Fix:

• Check loops like forever and repeat until to ensure they have appropriate conditions or exit points. For example: You could use repeat until touching edge to stop the loop when the sprite touches the screen’s edge.
• Add a wait [] seconds block to slow down the loop’s execution.

Alternatively if you are having issues with your sprite only moving or changing once, and you want it to change multiple times, put your code inside a forever block so that it keeps running.

10. Other sprites keep going in front of your sprite

Problem: My sprites keep going in front of my sprite.

Fix:

• You can control which sprite appears in front or behind by adjusting its layer. Scratch uses layers to determine the stacking order of sprites on the screen.
• Use the go to [front] layer block to make sure your main sprite always stays in front of others.
• You can also use go forward [number] layers or go backward [number] layers to fine-tune the position of the sprite among others.
• If you want a sprite to move behind others, use the go to [back] layer block.

For help with additional specific problems, see if other parents or educators are talking about them and have provided answers in the Scratch Discussions Forum.

Help Debugging Scratch Coding: Fix Common Scratch Code Problems

Also while you're helping your child, keep in mind that debugging is a fantastic opportunity to help your child develop a growth mindset, which is the belief that we can improve our abilities through effort and learning. When your child encounters a bug in their Scratch project, it’s not just a problem—it’s a chance for them to think critically, experiment with solutions, and build resilience. Encouraging your child to embrace mistakes as part of the learning process helps them understand that challenges are normal and that persistence leads to success. Debugging can show kids that there’s always a way to improve and figure things out, which is an invaluable skill both in coding and in life!

Now that your child knows how to fix common Scratch coding errors and has learned to approach problems with curiosity and confidence, empower them to bring all their ideas to life and create cool games and animations, by enrolling them in a live online Scratch class! They can even earn a certificate, while they build their creativity and problem solving skills. Start with a free introduction session.