Code diff checker

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Source code comparison tool

Paste or upload two source code files and compare them here

Use this dedicated code diff checker for JavaScript, TypeScript, Python, PHP, HTML, CSS, SQL, shell scripts, config files, and other text-based source files.

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Upload two files or paste content above, then select Compare Source Code.

How to read a code diff

A code diff is easiest to read when you keep the old version on the left and the new version on the right. Removed code shows what existed in the baseline. Added code shows what the revised file introduces. Modified lines deserve the closest review because they often change behavior while looking visually small.

Before comparing, format both files with the same formatter when possible. Mixing formatted and unformatted code creates noisy diffs where indentation dominates the review. If you are comparing a small snippet copied from a pull request, include a few surrounding lines so the changed function, selector, query, or condition is easier to understand.

Code guide

What to check during code comparison

Behavior changes

Focus on conditions, return values, validation rules, SQL filters, loop boundaries, and error handling. These lines can change output even when the edit is short.

Dependencies and config

Review package files, environment examples, feature flags, routes, and build settings carefully because they affect runtime behavior outside the edited function.

Whitespace noise

If the diff is mostly spacing, run a formatter on both versions and compare again. A cleaner diff helps you find the meaningful logic change.

Copy the result

Use the copied report when you need to paste a short review into a ticket, issue, release note, or chat discussion.

Example comparison

JavaScript validation change example

This example shows a small logic update where the changed file adds trimming and a minimum length check.

Original code

function isValidName(name) {
  if (!name) {
    return false;
  }
  return name.length > 0;
}

Changed code

function isValidName(name) {
  const value = String(name || "").trim();
  if (!value) {
    return false;
  }
  return value.length >= 2;
}

Code review use cases

FileDiffChecker.com can help with quick checks for PHP template edits, JavaScript changes, TypeScript refactors, CSS updates, SQL query revisions, shell script edits, Markdown documentation, and configuration updates. It is especially useful when you need a quick visual comparison outside a full Git workflow.

The tool supports text-based source files including .php, .py, .js, .ts, .java, .html, .css, .toml, .yaml, .sql, .sh, .go, .rs, .rb, .cs, .cpp, .swift, .kt, and .vue. For binary files, compiled files, or large generated bundles, use a specialized developer tool instead.

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