Compare two pieces of text or code side by side. Instantly find additions, removals, and changes with color-coded diff output.
A text difference checker (also called a diff tool or online difference checker) is a utility that compares two blocks of text or code and highlights the differences between them. It identifies which lines have been added, removed, or changed, making it easy to spot modifications at a glance. Whether you're comparing documents, reviewing code changes, or checking revisions, a text difference checker saves hours of manual comparison.
Using our free text comparison tool is simple and takes just a few steps:
You can also upload files directly using the upload button on each editor, or use the Swap button to reverse the comparison direction.
A text comparison tool and code difference tool are invaluable in many scenarios:
Developers use diff tools daily to review code changes before merging. Compare your working copy against the original to catch bugs, unintended changes, or missing lines. Our code difference tool handles any programming language — JavaScript, Python, HTML, CSS, SQL, and more.
When editing essays, articles, or reports, compare the original draft with the revised version. Quickly spot what was added, deleted, or reworded without reading both documents line by line.
Lawyers and professionals use text comparison to identify changes between contract versions. Even a single word change in a legal document can have significant implications — a diff tool ensures nothing is missed.
System administrators compare configuration files to find what changed between deployments or server setups. Upload your config files and instantly see every modification.
Writers and editors can track changes between article revisions, blog post drafts, or CMS content updates. The diff output clearly shows the evolution of your content over time.
Our tool uses a Longest Common Subsequence (LCS) algorithm to find differences between texts. Here's how it works:
This approach ensures accurate, line-by-line comparison that handles insertions, deletions, and modifications reliably.
Need to do file comparison online? Our tool supports direct file uploads in numerous formats including .txt, .js, .py, .html, .css, .json, .xml, .md, .csv, and many more. Simply click the upload button on either editor panel, select your file, and the contents will be loaded automatically. You can then compare files online instantly — no software installation required.
There are many reasons to choose our free difference tool over alternatives:
Our difference checker tool is designed for speed, accuracy, and ease of use — whether you're a developer, writer, lawyer, or student.
A difference checker (or diff tool) is a software utility that compares two sets of text or code and identifies what has been added, removed, or changed between them. It displays results with color coding — typically green for additions and red for removals — making it easy to review changes at a glance.
Paste your original text in the left editor and the changed version in the right editor, then click "Find Differences." The tool will instantly analyze both texts and display the differences with color-coded highlighting. You can also upload files directly.
Yes. This tool is designed to handle both plain text and source code in any programming language. The monospace font, line numbers, and line-by-line comparison make it ideal for code review in JavaScript, Python, HTML, CSS, PHP, Java, C#, SQL, and more.
Yes, completely free. There are no usage limits, no premium features locked behind a paywall, and no registration required. Use it as much as you need.
Our tool uses a Longest Common Subsequence (LCS) algorithm. It splits both inputs into lines, then computes the longest sequence of matching lines. Any lines not in this common sequence are marked as additions or removals, giving you an accurate line-by-line diff.
Yes. Click the upload button (📂) on either editor panel to select a file from your device. Supported formats include .txt, .js, .py, .html, .css, .json, .xml, .md, .csv, and many other text-based file types.
The tool supports any text-based file format including plain text (.txt), source code files (.js, .ts, .py, .html, .css, .php, .java, .go, .rb, .c, .cpp), data files (.json, .xml, .csv, .yaml), config files (.ini, .toml, .cfg), markdown (.md), SQL files, shell scripts, and more.
Absolutely. All text processing happens entirely in your browser using JavaScript. Your text is never sent to any server, never stored, and never shared. Your data stays on your device at all times.
You can copy the diff output to your clipboard using the "Copy Diff" button. You can also download the original or changed text as .txt files using the download button on each editor panel.
There is no hard limit. The tool runs in your browser, so it can handle texts of any reasonable length. Very large files (over 100,000 lines) may take a moment to process depending on your device's performance.
A unified diff shows all changes in a single column with additions and removals interleaved and color-coded. A side-by-side diff displays the original and changed text in two parallel columns, making it easy to compare corresponding lines visually. Both views are available in this tool.
Yes. The tool is fully responsive. On mobile devices, the two editor panels stack vertically for comfortable use, and all features including file upload, copy, and diff views work perfectly on phones and tablets.