Code Syntax Checker
Paste a snippet that will not run and find out why. The checker flags syntax problems, and the AI enhancement explains the error in plain language with a suggested fix, like having a patient senior dev on call.
How to use
- Paste your code snippet into the input box.
- Enable the AI enhancement for an explanation and suggested fix.
- Click Run to see what is wrong.
Syntax errors are the most common and least informative failures in programming. The interpreter tells you where it gave up parsing, which is often lines away from the actual mistake, a missing closing bracket on line 12 surfaces as 'unexpected token' on line 20, and a forgotten colon in Python points at the line after the real problem.
The classic offenders are unbalanced delimiters (brackets, braces, quotes), missing separators (commas in lists and objects, semicolons where the language demands them), indentation errors in whitespace-significant languages, and smart quotes pasted from documents or chat apps, those curly quotes look identical to straight quotes but are different characters entirely, and they break parsing in almost every language.
That last one deserves emphasis: code copied from Slack, Word, Notion, or a rendered web page frequently arrives with typographic quotes, non-breaking spaces, or zero-width characters that are invisible in most editors. If code that 'looks right' refuses to parse, invisible characters are the first thing to suspect.
The AI enhancement reads your snippet, identifies the actual root cause rather than the symptom line, and explains the fix, which is most valuable for beginners who have not yet built the pattern library that makes experienced developers spot a missing brace at a glance.
Examples
Input: def greet(name)
return f'Hello {name}'
Output: SyntaxError near line 1: function definition is missing ':' after the parameter listInput: print(“hello”)
Output: Error: U+201C curly quotes found, replace with straight quotes: print("hello")Frequently asked questions
Which languages can it check?
Common scripting and web languages, Python, JavaScript, JSON-like structures, and general bracket/quote balance for most C-family syntaxes. It is a snippet checker, not a full compiler: it finds parse-level problems, not logic bugs.
Why does my copied code fail when it looks correct?
Almost always invisible characters: curly quotes from word processors, non-breaking spaces, or zero-width characters from web pages. The checker detects and points these out, they are the most common cause of 'but it looks fine' errors.
What does the AI explanation add over the raw error?
Raw parser errors point at where parsing failed, not what caused it. The AI identifies the root cause, the unclosed bracket three lines earlier, and shows the corrected code. 10 free AI runs per day.
Is my code stored?
No, anonymous runs are stateless and nothing is persisted. As with any online tool, avoid pasting proprietary code containing secrets. Strip API keys first.
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