Free Developer Tool — 100% Client-Side

Text Diff Checker

Compare two texts side by side and highlight the differences between them.

Original Text

Changed Text

Diff Output

What Is a Text Diff?

A text diff (short for difference) is a comparison between two blocks of text that identifies what has been added, removed, or changed. A diff checker or diff tool performs this comparison automatically, line by line, and highlights the differences using color coding. Our free online text diff checker runs entirely in your browser so your data never leaves your machine.

Common Use Cases for Diff Tools

Code Reviews — Compare code changes between commits or pull requests to catch bugs and review modifications before merging.
Document Versioning — Track revisions in documentation, legal contracts, or academic papers across multiple drafts.
Configuration Management — Spot differences between configuration files across environments (dev, staging, production).
Data Migration Verification — Compare CSV exports, database dumps, or JSON payloads before and after data transformations.
Debugging — Isolate unexpected changes in log files, error traces, or generated output during troubleshooting.

How to Use This Text Diff Checker

Using this text comparison tool is simple. Paste your original text into the left textarea and your modified text into the right textarea. Click Compare to generate the diff. The output will display each line with a prefix: lines that match are shown with two spaces, added lines are prefixed with +, and removed lines are prefixed with -. Use the Copy button to copy the diff result to your clipboard.

Understanding Diff Output

The diff output uses clear visual cues. Lines shown in green with a + prefix are lines that appear only in the changed text — these are additions. Lines shown in red with a - prefix are lines that appear only in the original text — these are deletions. Lines with no color and two spaces are identical in both versions. When a line is modified, the original line appears in red and the new version appears in green. This line-by-line diff comparison makes it easy to spot exactly what changed at a glance.

How to Do This in Code

import { diffChars } from 'diff';
const changes = diffChars(oldText, newText);
changes.forEach(part => {
  const color = part.added ? 'green' : part.removed ? 'red' : 'grey';
  console.log(`%c${part.value}`, `color: ${color}`);
});

import difflib
diff = difflib.unified_diff(old.splitlines(), new.splitlines(), lineterm='')
print('\n'.join(diff))

diff -u file1.txt file2.txt
# or with colordiff:
colordiff -u file1.txt file2.txt

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