AI Code Debugger & Bug Finder
Static analysis + bug finder for Python, JavaScript, TypeScript, Java, C++, and Go. Detects undefined variables, missing returns, off-by-one loops, = vs == bugs, == vs === in JS, mutable default arguments, var usage, console.log leftovers, TODO/FIXME markers, empty catch blocks, magic numbers, infinite loops, unreachable code, missing break in switch, hardcoded credentials, division-by-zero literals, mismatched brackets, and more. Per-language rule sets, severity classification (info/warning/error/critical), line numbers, suggested fixes, auto-fix button for safe corrections, side-by-side diff view, runtime-error root-cause guesser, cyclomatic complexity hint, code-smell detection, sample buggy snippets, stats per severity, local history (localStorage, last 20), and shareable URL. 100% client-side. Optional BYO-key LLM enhancement for explanations — your code never leaves the browser unless you choose to call your own provider.
About AI Code Debugger & Bug Finder
Static analysis + bug finder for Python, JavaScript, TypeScript, Java, C++, and Go. Detects undefined variables, missing returns, off-by-one loops, = vs == bugs, == vs === in JS, mutable default arguments, var usage, console.log leftovers, TODO/FIXME markers, empty catch blocks, magic numbers, infinite loops, unreachable code, missing break in switch, hardcoded credentials, division-by-zero literals, mismatched brackets, and more. Per-language rule sets, severity classification (info/warning/error/critical), line numbers, suggested fixes, auto-fix button for safe corrections, side-by-side diff view, runtime-error root-cause guesser, cyclomatic complexity hint, code-smell detection, sample buggy snippets, stats per severity, local history (localStorage, last 20), and shareable URL. 100% client-side. Optional BYO-key LLM enhancement for explanations — your code never leaves the browser unless you choose to call your own provider. Everything runs locally in your browser — your data never leaves your device.
How to use
- Enter your input in the tool above.
- Adjust any options to your preference.
- Use the Copy or Download buttons to save the result.
- Everything happens locally — your data never leaves your browser.
FAQ
How does the AI code debugger work?
Pick a language (or let the tool auto-detect) and paste your code. The tool runs deterministic, pattern-based static analysis using per-language rule sets — finding undefined variables, missing returns, off-by-one loops, = vs == bugs, == vs === in JavaScript, mutable default arguments in Python, var usage, leftover console.log, TODO/FIXME markers, empty catch blocks, magic numbers, infinite loops, unreachable code after return, missing break in switch, hardcoded credentials, division-by-zero literals, and mismatched brackets. Each issue has a line number, severity, explanation, and suggested fix. The optional LLM enhancement uses your own key to explain tricky issues — never touching UnQTools servers.
What languages are supported?
Python, JavaScript, TypeScript, Java, C++, and Go. Each language has its own rule set tuned to its common pitfalls. JavaScript/TypeScript rules flag var usage, == vs ===, and missing semicolons. Python rules flag mutable default arguments (def f(x=[])) and bare except. Java/C++ rules flag missing semicolons and missing break in switch. Go rules flag unused-likely patterns. Mismatched-bracket detection runs for all languages.
Are the findings always correct?
No — and the tool is honest about it. Pattern-based static analysis catches common issues reliably (bracket mismatches, var declarations, console.log leftovers, TODO markers, = vs ==, missing break in switch). Other findings (undefined variables, missing returns, unreachable code) are heuristic and may produce false positives or miss real bugs — always review each finding before changing your code. The tool clearly labels findings as 'deterministic' (rule-based, reliable) vs 'heuristic' (best-effort, review needed). Optional BYO-key LLM enhancement can refine explanations.
Can the tool auto-fix issues?
Yes — for safe, deterministic fixes. The 'Auto-fix' button applies only safe corrections: converting `var` to `let`, inserting missing semicolons, replacing `==` with `===` (and `!=` with `!==`) in JavaScript/TypeScript, and adding `break` statements to switch cases that are missing them. Each applied fix is listed so you can review what changed. Heuristic findings (undefined variables, missing returns, etc.) are NOT auto-fixed — they need your judgment.
What extra features does this tool have?
(1) 6 languages with per-language rule sets. (2) Auto-detect source language. (3) 15+ bug-detection rules (undefined vars, missing returns, off-by-one, == vs ===, var usage, console.log, TODO/FIXME, empty catch, magic numbers, infinite loops, unreachable code, missing break, hardcoded credentials, division by zero, mismatched brackets). (4) Severity classification (info / warning / error / critical). (5) Line numbers + suggested fixes per issue. (6) Auto-fix button for safe corrections. (7) Side-by-side diff view (before vs after). (8) Runtime-error root-cause guesser (paste an error message). (9) Cyclomatic complexity hint. (10) Code-smell detection (long functions, deep nesting). (11) Sample buggy snippets per language. (12) Stats per severity. (13) Local history (localStorage, last 20). (14) Shareable URL with code + language encoded. (15) Optional BYO-key LLM explanation (OpenAI/Anthropic). (16) Honesty disclaimer about heuristic findings.
Is my code sent anywhere?
No. All static analysis, auto-fixes, complexity calculation, and history run locally in your browser — your code never leaves this device. The only network path is if you explicitly paste your own LLM API key and click 'Explain with LLM' — that request goes directly to your chosen LLM provider (OpenAI or Anthropic) and never touches UnQTools servers. Skip the LLM step for 100% offline use.
Related tools
AI .htaccess Redirect Generator
Generate Apache .htaccess redirect and rewrite rules from bulk old→new URL pairs or plain-language intent. Supports 301 permanent, 302 temporary, 307, RedirectMatch, RewriteRule with regex capture groups, www/non-www canonicalization, HTTP→HTTPS, hotlink protection, custom error pages, and IP allow/block. Per-rule explanations, sample-URL tester emulating mod_rewrite, and redirect-loop detection. Pure-JS engine — optional BYO-key LLM. 100% client-side, no upload.
AI Alt Text Generator for Images
Generate WCAG-friendly alt text for images. On-device metadata extractor (dimensions, format, dominant color, filename → suggest), context-aware descriptive templates, decorative vs informative vs complex classifier, length meter, 'don't start with image of' linter, optional SEO keyword weaving, 100+ language templates, batch CSV/JSON export, optional BYO-key LLM caption enhancement. 100% client-side — images never uploaded.
AI Analogies Generator
Explain any concept with tailored analogies across 10+ domains (cooking, sports, nature, technology, music, business, science, everyday life, kids, vehicles). Pure-JS analogy template engine with metaphor / simile / story styles, complexity levels, 'where it breaks down' honesty notes, explainer expansion, concept keyword extractor, audience presets, optional BYO-key LLM enhancement. 100% client-side — nothing uploaded.