Look something up
Need to check what an HTML attribute does or how a CSS property works? Each topic has syntax and examples you can use while you’re writing code.
Browse documentationUnderstand the code,
whoever wrote it
Look up the part you don’t understand, then open an example in the Playground to see what changes when you edit it.
JavaScript / Arrays
Try selecting an item from an array
Arrays let you keep multiple values together in an ordered list. Choose a position and see what it contains.
arrays.js
const languages = ["HTML","CSS","JavaScript"];
console.log(languages[0]);Output
Choose a position, then select “Show output”.
Why Codectionary?
It’s easy to copy an example and still be unsure why it works.
Changing an array index from 0 to 1 gives you a different result. Knowing why means you can use that idea in your own project. Codectionary keeps the explanation alongside the example, so you can work through the detail you’re missing.
Stuck on an error? Ask the AI assistant about the message, then test its suggestion in your code. Use the docs to check any unfamiliar syntax.
Choose a language
Browse syntax and examples across 12 languages.
Planned additions: Go, Rust, Kotlin, Swift and Dart.
Keep learning here
Work through an example
Open the starter page and change the heading in index.html. The preview shows your edit; JavaScript logs and errors appear in the Console below.
Open PlaygroundFlashcards
Choose a topic and try answering before you turn the card over.
Quizzes
Choose a language and difficulty. Each answer comes with an explanation.
Watch
Browse selected tutorials, with links to related docs when there’s a useful match.
AI assistant
Paste the error message you’re stuck on and ask what could be causing it.
Common questions
Is Codectionary free to use?
Yes. The documentation and learning tools are free to use. Quizzes, flashcards and the AI assistant require a free account.
Do I need an account to get started?
You can read the docs, use the Playground and browse Watch without signing in. You’ll need a free account for quizzes, flashcards, the AI assistant or submitting a tutorial.
Where should I start?
If you want to build a web page, start with the HTML documentation. Open an example with “Edit in Playground” and change a heading or add a link. Try CSS when you want to change how the page looks.
Can I save Playground projects?
Not yet. Copy each file’s code to your device before leaving the Playground or refreshing the page. Project files aren’t saved to your account, and there isn’t a ZIP download option. The browser remembers your editor settings and panel layout.
Does code run in my browser?
HTML and CSS render in the browser preview; JavaScript and TypeScript run there too. Java and C++ use a separate execution service when it is available. Python files can be edited, but their Run control is temporarily paused while the runner is isolated. C#, Ruby, PHP, Lua and Luau are editing-only. Run Roblox examples in Roblox Studio.
Where do Watch tutorials come from?
Watch links to tutorials on YouTube and Vimeo. Codectionary Picks are selected for the library; Community Tutorials are suggestions reviewed before publication. Videos open on the original platform. You can suggest a link using “Submit a tutorial”.
Does the AI assistant write my code for me?
It can suggest code and explain errors in the chat, but it doesn’t edit your Playground files. Share a small example or an error message, then test any suggestion in your own code.