JavaScript Diff Checker — Compare JS Code Online
Paste two JavaScript files and instantly see every added function, removed line, and changed logic. Syntax highlighting included. No account. No limits.
Paste text in both panels above to compare
Or to see how it works
Compare JavaScript file versions
Paste two versions of a .js file to see exactly what changed between them. Great for reviewing refactors, tracing regressions, or auditing third-party script updates before deploying to production.
Review JavaScript code changes
Copy the old and new versions of a function or module directly from your editor or GitHub. The diff highlights added functions, removed variables, and changed expressions with character-level precision — faster than reading a full file diff.
JavaScript syntax highlighting
Unlike plain text diff tools, DiffCheck applies JavaScript syntax coloring on top of the diff highlighting. Keywords, strings, function names, and operators are color-coded — making it much easier to parse complex JS diffs at a glance.
Spot logic changes character by character
When a condition tightens or a variable renames, character-level highlighting shows the exact change inside the line — not just that the line changed. Spot a single operator difference or a renamed identifier in dense JavaScript without reading the whole line.
Privacy-first — runs in your browser
JavaScript source code often contains business logic, API integrations, and proprietary algorithms. DiffCheck never sends your code to any server. All comparison runs locally in JavaScript — safe for internal codebases, unreleased features, and sensitive scripts.
Works for TypeScript too
Switch the language selector to TypeScript for .ts and .tsx files. Type annotations, interfaces, and generics are syntax-highlighted on top of the diff, making TypeScript code reviews significantly cleaner to read.
How to compare JavaScript code online
- 1
Paste your original JavaScript
Put the first version of your JS file or function in the left editor — this is your baseline. Works with any JavaScript: ES modules, CommonJS, browser scripts, or Node.js code.
- 2
Paste your modified JavaScript
Put the updated version in the right editor. This is what you're comparing against the original — a refactored function, an updated dependency version, or a patched script.
- 3
Read the diff
Green lines were added; red lines were removed. Within changed lines, the exact characters that differ are highlighted more intensely. JavaScript is selected by default for syntax coloring.
- 4
Switch views as needed
Use side-by-side to review both JS files in parallel columns, or switch to inline view for a compact change summary. The statistics bar shows total lines added, removed, and unchanged.
Frequently asked questions
What is a JavaScript diff checker?
A JavaScript diff checker compares two JS files or code snippets and highlights the differences — added functions, removed lines, changed variable names, and modified logic. It's essential for code review, debugging, and comparing versions of a script.
Is this JavaScript diff tool free?
Yes, completely free with no rate limits and no signup. All JavaScript comparison runs in your browser — your code never leaves your device.
Can I compare minified JavaScript?
Yes, but the diff will be hard to read since minified JS is usually one long line. For a meaningful diff, pretty-print or format both JS files before comparing — each statement on its own line makes it easy to see exactly what changed.
Is my JavaScript code safe to paste here?
Yes. All diff computation runs locally in your browser using JavaScript. Your code is never sent to any server, never stored, and never logged. Safe to use with proprietary code, API keys embedded in scripts, or any sensitive JavaScript.
Can I use this to review JavaScript pull requests?
Absolutely. Paste the old version of a file on the left and the new version on the right. The diff shows exactly what functions were added, what logic was removed, and which lines changed — with JavaScript syntax highlighting to make it easy to read.
Does it work for TypeScript too?
Yes. Switch the language selector to TypeScript for syntax highlighting tailored to .ts and .tsx files. TypeScript-specific syntax like type annotations, interfaces, and generics will be color-coded on top of the diff.