Text Compare
Compare two texts online and find differences instantly. Highlight changes line-by-line, word-by-word, or character-by-character with a fast browser-based diff checker.
Comparison Results
Side-by-Side Dual View • Level: line
Compare two texts to see their differences here.
Paste original and modified text in the boxes above to highlight additions, deletions, and edits.
How to Compare Two Texts Online
Add Original Text
Paste your first draft or upload a text file into the Original box.
Add Modified Text
Paste or upload the revised version into the Modified box.
Select Level
Choose Line, Word, or Character comparison level.
Configure Rules
Toggle Ignore Case or Ignore Whitespace as needed.
Review Differences
Inspect highlighted additions, deletions, and copy exports.
Line, Word, and Character Comparison
Line-Level Diff
Best for source code, configuration files, logs, and structured documents. Identifies entire added, removed, or changed lines.
Word-Level Diff
Best for prose, articles, draft revisions, proofreading, and legal documents. Highlights exact words inserted or deleted inside sentences.
Character-Level Diff
Best for fixing typos, variable names, short strings, and exact textual changes. Pinpoints individual character modifications.
Side-by-Side vs. Unified Diff
| View | Best For | Representation |
|---|---|---|
| Side-by-Side | Document review & draft comparison | Two parallel columns displaying original and modified versions |
| Unified | Code review & compact inspection | Git-style sequential timeline with + and - line prefixes |
Common Text Comparison Use Cases
For Writers and Editors
Compare article drafts, proofreading edits, email revisions, and student assignments to trace changes between revisions.
For Developers and QA
Compare source code snippets, patch files, API payloads, environment configs, and test outputs without opening an IDE.
For Logs & Config Files
Compare server configuration files, Dockerfiles, build logs, and environment variables to diagnose deployment bugs.
Compare Structured Data
Comparing JSON, XML, YAML, or SQL often requires structure-aware comparison rather than plain text diffing.
Overview
The ToolMono Text Diff Checker is an enterprise-grade software engineering, technical writing, and document comparison utility. Inspecting deltas between source code commits, legal agreements, API payloads, or article drafts is essential for catching bugs and tracking revisions.
ToolMono implements the industry-standard Myers Diff Algorithm (Longest Common Subsequence - LCS) to compute exact character-level, word-level, and line-level difference matrices completely local inside your web browser sandbox. Features include Side-by-Side split and Unified inline view modes, whitespace and case normalization options, jump-to-difference controls, multi-format file uploads (TXT, JSON, XML, CSV, Markdown, HTML, JS, TS, YAML), exportable HTML/Markdown reports, and 100% browser privacy.
ToolMono operates 100% client-side. For complementary formatting, writing, and code tools, explore our JSON Formatter, Text Case Converter, Regex Tester, and Word Counter.
Comparison Engine & Views (Side-by-Side, Unified)
ToolMono offers two distinct visual layout views:
Displays Original and Modified documents in dual parallel columns with synchronized scrolling and line number tracking.
Merges changes into a single continuous stream (Git patch style) with clear + and - prefix indicators.
Line, Word & Character Level Diff Modes
| Granularity Mode | Underlying Function | Best Application Use Case |
|---|---|---|
| Line-Level Diff | diffLines | Source code refactoring, JSON files, XML, and structured configuration files. |
| Word-Level Diff | diffWords | Blog posts, technical documentation, manuscripts, and legal contracts. |
| Character-Level Diff | diffChars | Spotting single-character typos, variable name changes, and minified strings. |
Comparison Rules (Ignore Whitespace, Ignore Case)
Granular Normalization Settings
Ignore Whitespace
Ignores spaces and tab indentations to prevent false positives when auto-formatting code.
Ignore Blank Lines
Filters out empty newlines between paragraphs or functions.
Ignore Case
Case-insensitive comparison normalizing uppercase and lowercase characters.
Ignore Line Endings
Normalizes Windows CRLF (\r\n) vs Unix LF (\n) line breaks.
File Upload & Code Format Support
Drag & Drop Multi-Format File Reader
ToolMono natively parses plain text (.txt), JSON (.json), XML (.xml), CSV (.csv), Markdown (.md), HTML (.html), CSS (.css), JavaScript (.js), TypeScript (.ts), and YAML (.yaml) files directly via drag & drop or file pickers.
Code Examples (9 Languages/Libraries)
Select your target programming language or library to view text diff calculation code:
// Node.js - Using 'diff' package (Myers Algorithm)
const { diffLines, diffWords } = require('diff');
const original = "function add(a, b) {
return a + b;
}";
const modified = "function add(a, b, c) {
return a + b + c;
}";
// Line-level diff
const lineDiff = diffLines(original, modified);
lineDiff.forEach((part) => {
const symbol = part.added ? '+' : part.removed ? '-' : ' ';
console.log(`${symbol} ${part.value.trim()}`);
});
// Word-level diff
const wordDiff = diffWords("Hello world", "Hello brave new world");
console.log(wordDiff);Reference & Algorithm Comparison Tables
1. Diff Algorithm Comparison Matrix
| Algorithm | Time Complexity | Primary Advantage |
|---|---|---|
| Myers Algorithm (LCS) | O((N + M) D) | Industry standard (Git). Generates shortest edit script. |
| Patience Diff | O(N log N) | Excellent for heavily reordered functions and code blocks. |
| Levenshtein Distance | O(N * M) | Fuzzy string distance matching for spellcheck. |
What is a Text Diff Checker & How Myers Algorithm Works?
Published by Eugene W. Myers in 1986, the Myers Diff algorithm models difference calculation as finding the Shortest Edit Path on an Edit Graph. It identifies the Longest Common Subsequence (LCS) between sequences to output minimum insertions and deletions.
AI Overview Answers
What is a Text Diff Checker?
A Text Diff Checker is a utility that compares two documents or code snippets and computes the exact delta, highlighting added lines in green and removed lines in red.
Is my text private when using ToolMono?
Yes. 100% of diff matrix calculations run locally in your browser memory. Your confidential code, legal contracts, and text are never uploaded to any server.
How to Use ToolMono Text Diff Checker
Paste / Upload
Paste original & modified text or drop files.
Select View Mode
Choose Side-by-Side Split or Unified Inline.
Select Granularity
Choose Line-level, Word-level, or Char-level.
Set Rules
Toggle Ignore Whitespace, Case, or Blank Lines.
Copy / Export
Download HTML, Markdown, TXT, or print PDF.
Code Review & Text Editing Best Practices
Enable Ignore Whitespace on Prettified Code
Always enable 'Ignore Whitespace' when comparing code that has been formatted by Prettier or ESLint to suppress tab/space noise.
Use Word-Level Diffing for Prose & Manuscripts
Word-level diffing isolates individual word substitutions in long paragraphs rather than marking the whole sentence red/green.
Common Mistakes & Fixes
Line Ending Differences (CRLF vs LF)
If every line in your document appears modified, the files use different OS line endings. Toggle 'Ignore Line Endings'.
Tips & Tricks
Export HTML Reports for Code Reviews
Download self-contained HTML diff reports to share code review proofs with teammates offline.
Frequently Asked Questions
Privacy & E-E-A-T Verification
100% Client-Side Browser Privacy Guarantee
ToolMono operates under strict privacy guarantees. All diff calculations, Myers algorithm matrix execution, and report exports run 100% locally inside your web browser. No text, code, or files are ever transmitted to remote servers.
- Myers Diff Algorithm (LCS) Powered
- Zero Network Server Uploads
- HTML & Markdown Report Export
- 100% Offline Capable
References & Standards
Unified Diff Format Specification (GNU Diffutils)
Official documentation for unified diff patch headers and line markers.
Myers Diff Algorithm Research Paper
Authoritative reference for O(ND) greedy diff computation.
Git Diff Official Documentation
Official Git documentation for line-by-line and word-by-word file comparison.
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