Text & Document Diff Checker

Compare contracts, source code, or CSV documents side-by-side with colour-coded difference tracking and exportable reports.

+0 Added -0 Removed

Comparison Visualiser

Green = Added • Red = Removed
Report copied to clipboard

💡 Compare Anything Instantly

💻

Code & Script Revisions

Inspect code changes, JSON schemas, SQL migrations, and YAML configs line-by-line before committing.

Line & char diff →
⚖️

Legal Clauses & NDAs

Compare terms of service, tenancy agreements, and supplier contracts to flag inserted or removed clauses instantly.

Word-for-word accuracy →
✍️

Articles & Copywriting

Proofread manuscript drafts, marketing headlines, and translated texts to track editorial adjustments easily.

Sentence & word diff →
📊

CSV & Data Records

Audit spreadsheet exports, customer lists, price books, and inventory catalogs with exact highlighted delta counts.

Delta counts →

📋 How to Compare Text & Documents

  1. 1
    Input Documents: Paste text into Original (left) and Modified (right), or drag and drop files directly onto each box.
  2. 2
    Choose Comparison Mode: Select Words for prose, Lines for code/scripts, or Characters for typos.
  3. 3
    Select Visual Layout: Switch between Side-by-Side (split columns) or Unified (inline Git-style patch stream).
  4. 4
    Export or Copy: Copy the color-highlighted differences to your clipboard or download a detailed timestamped diff report.

✨ Diff Inspection Tips

  • ✓
    Side-by-Side vs Unified: Use Side-by-Side to review two complete pages in context; switch to Unified when you want a compact list of only what changed.
  • ✓
    Word vs Line Granularity: For programming source code and JSON, Line comparison is easiest to follow. For articles, contracts, and emails, Word mode highlights exact rewording.
  • ✓
    Swap Texts with One Click: Hit the Swap button to invert original and modified positions instantly without re-pasting.
🔒 100% Client-Side: Sensitive contracts, private passwords, and proprietary code never leave your computer.
⚙️
Technical Architecture Under the Hood: Eugene Myers' O((N+M)D) Difference Algorithm
Inspect Specs ▼

Shortest Edit Script (SES) & Memory Buffers

BWTools Diff Checker leverages a high-efficiency implementation of Eugene W. Myers' $O((N+M)D)$ greedy difference algorithm. By tokenising inputs into memory buffers, it identifies the shortest edit script (SES) with minimal compute cycles.

DOM rendering is performed cleanly through dynamic fragment reconstruction, preventing reflow thrashing during comparison of long files. UTF-8 file reading executes via native FileReader.readAsText() with zero network payload.

Diff Modes & Supported File Types

Comparison Mode Optimal For Supported File Types Layout Compatibility Privacy Guarantee
Word Diff Contracts, Legal Docs, Articles .txt, .md, .rtf, .doc Split & Unified 100% In-Browser
Line Diff Source Code, JSON, CSV Configs .js, .ts, .json, .csv, .yml Split & Unified 100% In-Browser
Character Diff Serial Numbers, Keys, Typo Audits Plain Text, Hashes Split & Unified 100% In-Browser
Sentence Diff Copywriting, Structural Rephrasing .txt, .md, Transcripts Split & Unified 100% In-Browser

❓ Frequently Asked Questions

Is my proprietary text or sensitive code uploaded to your servers? ▼

No. The diff engine executes 100% client-side inside your browser via local JavaScript. Nothing you paste, type, or load is ever transmitted across the internet, logged, or cached externally.

What is the difference between Split and Unified view? ▼

Split view renders two distinct columns allowing you to visually inspect the original and modified documents side-by-side. Unified view merges all changes into a single chronological stream, highlighting deletions and additions inline like a Git commit diff.

Can I drag and drop files directly into the editor? ▼

Yes. You can drag and drop any supported text file (.txt, .csv, .json, .js, etc.) directly into either textarea box to load its content automatically.

Can I download a report of all identified differences? ▼

Yes. Clicking Download Diff Report (.txt) saves an offline report complete with timestamps, chosen comparison mode, added/removed delta statistics, and full difference text.