Summary

This code explainer turns a pasted snippet into a plain-English outline: the language, each function and what its name suggests, a cyclomatic complexity score, and flags such as empty catch blocks, eval calls and hardcoded secrets. It is a rule-based reader, not a language model, so it describes structure rather than intent. Complexity follows McCabe's measure, where 10 or less per function is the recommended limit. The analysis runs in your browser and your code is never sent anywhere.

Paste Code, Get a Plain-English Outline of What It Does

This free code explainer reads a snippet in your browser and returns its functions, decision paths, error handling and red flags, so you know where to look before you read line by line.

Explain my code
Engineer reading unfamiliar code on a monitor with a notebook sketch of function boxes beside the keyboard

Code explainer

Paste a function or a short file. The outline updates as you type. Nothing leaves your browser.

Walkthrough

    Things to check

      Reading the output

      How to use the outline

      1. 1

        Paste the snippet

        One function or one file works best. Past a few hundred lines the outline stops being a summary and becomes a list.

      2. 2

        Check the lead sentence

        It names the language, counts functions and gives a complexity score. A score above 10 means the code has too many paths to hold in your head at once.

      3. 3

        Read the walkthrough

        Each function gets one line: what its name suggests, how long it is, how many paths it has, and whether it loops, waits or handles failures.

      4. 4

        Open the flags first

        If the tool lists an empty error handler or a credential-like string, start there. Those are the lines most likely to hurt you later.

      How it works

      What the explainer actually measures

      Structure from syntax

      It strips comments and strings, then matches function definitions, imports, classes, loops and branches for the language it detects. No guessing about what the code is for, only what it contains.

      Complexity you can verify

      The score is cyclomatic complexity: one plus every if, loop, case, catch and boolean operator. It is the same count a linter would give you, and the NIST structured testing report suggests keeping a function at 10 or below.

      Flags that match real bugs

      Eval or exec calls, empty catch blocks, hardcoded secrets, TODO notes, nesting past four levels and functions over 40 lines. Each rule exists because it points at code that is easy to misread.

      Where it stops

      A snippet explainer answers "what is in here", not "why is it here"

      The question a new engineer asks is rarely "what does this loop do". It is "why does the billing service call this function, and who else depends on it". A pasted snippet cannot answer that, because the answer lives in other files. This tool is built for the first pass: you have a function open, you have five minutes, and you want to know whether it is a ten-line helper or a tangle with six exit paths. It gives you that in a second and tells you where the risk is. For the second question you need search across the whole repository. That is the gap between reading one function and understanding how a system is wired, and it is where most onboarding time goes.

      • Use it on a single function or file, not a whole service
      • Treat the flags as prompts to look closer, not as findings
      • Switch to repo-wide search when the question is about callers and dependencies
      Two engineers at a laptop, one pointing at a line of source code while the other reads along

      Questions about the code explainer

      Is this code explainer free, and does my code leave my browser?
      It is free and needs no signup. The analysis runs entirely in your browser with plain JavaScript. Your snippet is never sent to a server, so you can paste internal code without a security review. The only thing recorded is an anonymous count that the tool was used.
      Is this an AI model that understands my code?
      No. It is a rule-based reader. It detects the language, finds functions, imports, branches, loops and error handling, and describes them using the names and structure it sees. That makes it fast and predictable, but it cannot know intent. If a function is called process() and does something surprising, the tool will not know.
      How is the complexity score calculated?
      It counts decision points (if, elif, for, while, case, catch or except, boolean and/or operators, ternaries) and adds one. That is the cyclomatic complexity measure McCabe proposed in 1976. A score of 10 or less is the limit the NIST structured testing report recommends for a single function.
      Which languages does it support?
      Python, JavaScript, TypeScript, Java, Go and Rust. Auto-detect looks at keywords and syntax. If it guesses wrong on a short snippet, pick the language from the dropdown. Other C-style languages often work, but function detection is less reliable.
      Why does it flag things like empty catch blocks and TODO comments?
      Those are the spots where a reader most often gets surprised later. An empty catch hides failures, a TODO marks a known gap, and a long or deeply nested function is hard to test. The flags are prompts to look closer, not verdicts.
      What is the difference between this and asking an AI chat about my code?
      A chat model can reason about intent, but only about what you paste. This tool shows structure in seconds with no model involved. Neither one knows how the snippet connects to the rest of your repo. For that you need a tool that has indexed the whole codebase.
      Can I use it to review a pull request?
      Yes. Pick the reviewer option and paste the changed function. You get a checklist with branch counts, error handling and red flags, which tells you where to spend your attention before you open the full diff.

      Understand the whole repo, not just one snippet

      codebasechat answers questions about your codebase in plain English, with the files and call sites that back each answer.

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