Summary

This AI code checker scans a pasted function or file against four real, rule-based signals: functions over 40 lines, nesting past 4 levels deep, TODO/FIXME density, and risky calls like JSON.parse or fetch left without a try/catch. It returns a 0-100 score with a line-by-line breakdown of what was deducted and why, entirely in your browser. No account, no upload, no black-box AI grading, just four checks any staff engineer would run by eye.

An AI Code Checker That Scores Real Red Flags, Not Vibes

Paste a function or file. Get a 0-100 score built from four checks a staff engineer would run by eye: function length, nesting depth, TODO backlog, and error handling, calculated live in your browser as you type.

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AI code checker

Paste a function or a whole file below. The score and breakdown update as you type.

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Runs entirely in your browser. Nothing is uploaded.

    How it works

    Four checks, no black box

    Structure: length and nesting

    Functions are flagged past 40 lines, matching ESLint's own max-lines-per-function default of 50 with some margin. Nesting depth is tracked by brace counting for curly-brace languages, or an indentation-depth fallback for Python-style code, and flagged past 4 levels deep, the point most style guides call unreadable.

    Error handling

    The scanner looks for risky calls: JSON.parse, fetch, await, .then, execSync, requests., os.system. Then it checks whether a try/catch exists anywhere in the pasted code. Risky call with no guard nearby means a deduction, not a free pass.

    Housekeeping

    TODO, FIXME, XXX, and HACK markers are counted and normalized per 100 lines of code. One or two in a file is normal engineering. A dense backlog of them is a signal the file needs a pass before it ships, not after.

    Why these four checks, and not a real linter

    ESLint, pylint, and their equivalents parse an abstract syntax tree, which is why they can catch unused variables, unreachable branches, and type mismatches. This tool doesn't do that. It's a text scanner you can run on a snippet with no build step, no config file, and no install, useful for the ten seconds between finishing a function and opening a pull request. The tradeoff is honest: fewer, coarser checks, computed transparently, versus a real static analyzer's deeper but slower setup. If a team already runs ESLint or pylint in CI, keep running it. This tool is for the gap before that, when code isn't in a repo yet.

    Questions about the score

    Is this AI code checker actually free?
    Yes. It runs entirely in your browser with no signup, no API key, and no usage cap. There's no server involved in the scoring, so there's nothing to meter or bill.
    Does my code get uploaded anywhere?
    No. The scan runs as plain JavaScript in your tab, against the text sitting in the textarea. Nothing is sent to a server, stored, or logged, except an anonymous tool-run event with no code content, used only to see that the widget got used.
    What counts as an AI code checker here, versus a real linter?
    This is a heuristic scanner, not a compiler or a linter like ESLint or pylint. It doesn't parse an AST, so it can't catch type errors, unused variables, or dead code paths. It flags four structural patterns instead: long functions, deep nesting, TODO density, and risky calls without a try/catch nearby.
    Which languages does it work with?
    Anything brace-delimited works well: JavaScript, TypeScript, Java, C, C#, Go, Rust, PHP, Swift. Nesting is measured by counting matched braces. Indentation-only languages like Python fall back to an indentation-depth check instead. Mixed tabs and spaces, or unusual formatting, can throw off the nesting count either way.
    Why did a function I think is clean get flagged?
    Usually one of two things: a JSON.parse, fetch, or await call with no try/catch anywhere in the pasted snippet, or nesting that goes past 4 levels deep somewhere in the block. Paste more context, including the surrounding try block if there is one, and the score updates live as you type.
    Where do the thresholds (40 lines, depth 4, and so on) come from?
    They track common defaults in real linter configs: ESLint's max-lines-per-function rule defaults to 50 lines, and most internal style guides flag nesting past 3 to 4 levels as a readability problem. We set ours slightly under those defaults, on the strict side, because a scanner without full AST parsing needs a wider safety margin than a real linter does.
    Can this replace a code review?
    No, and it shouldn't try to. It's a five-second gut check before you open a pull request, not a reviewer. It catches structural smells, not logic bugs, security issues, or architecture problems. Use it before review, not instead of one.
    My score is 100 but the code still feels messy. Is the tool wrong?
    It's checking four specific things, not general code quality. A 100 means no long functions, no deep nesting, no TODO backlog, and no unguarded risky calls. It doesn't mean the naming is good, the tests exist, or the architecture makes sense six months from now.
    Does pasting a partial snippet skew the score?
    Yes, and that's expected. If you paste a function body without the try/catch that wraps it elsewhere in the file, the checker has no way to know that guard exists. For an accurate read, paste the smallest self-contained unit: one function, or one file.

    This checks structure. CodebaseChat answers the harder question.

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