# Expression Troubleshooting ## Introduction This guide covers common After Effects expression errors and quick fixes. Follow these steps to troubleshoot, and find out how to ask for help if needed. ## Most Common Issue {% hint style="danger" %} The wrong Expression Engine (ExtendScript) is being used.\ \ **Fix:** \ **1. G**o to File > Project Settings > Expressions\ 2\. Change the Expression Engine to **JavaScript** ([available on AE 2019 and later.](https://help.pixflow.net/portal/en/kb/articles/after-effect-change-expression-engin)) {% endhint %}
## Other Common Issues * **Typos or Case Sensitivity Errors:** Double-check that variable or function names are spelled correctly and have the right case (JavaScript is case-sensitive). * **Single Value Instead of an Array:** If you assign a single value to properties that expect an array (e.g., Scale), you will get an error. ```javascript myScale = 5; // Incorrect myScale = [5, 5]; // Correct myScale = 5; s = [myScale, myScale]; // Another correct option ``` * [ ] **Missing Semicolons:** Make sure to end each line with a semicolon `;` * [ ] **String vs. Variable Confusion:** Listing a variable as a string when it shouldn’t be. **Example:**\ `"`myText" is a string, whereas `myText` is a variable. ## **When to ask for help?** If you tried everything above, and nothing still works. There are two things you can do: 1. You can **download the tutorial project files** that I usually provide for free on my [Gumroad](https://nosleepcreative.gumroad.com/?recommended_by=more_like_this), and copy and paste my code into your projects to get it to work. From there, you can also compare what I have written and your code to see where is the mistake. 2. **If you have to ask me for help,** what I appreciate is having **more context and description** of your problem. For example: * Which lines does the error occurred? * What does the error(s) say? * What have you tried? * Have you consulted this guide and tried the solutions I mentioned? * What AE version are you running, and what OS. **Sample format for requesting troubleshooting** *Hello, I having `problem` with `line number`. The error says `errorMessage` . I have tried `solution` but I still cannot fix the issue.* ### **What doesn't help** 1. Saying that "I wrote the code exactly" or I followed your tutorial. If it didn’t work, something else is likely wrong—usually a small typo. 2. Provide as much detail as possible so I can help you quickly. ## More readings * [How to troubleshoot expressions errors](https://www.youtube.com/watch?v=VdaGqq4I0qM\&t=1426s), Intro to Expression Rigs in After Effects, Zack Lovatt