🔍 What is Text Compare & Merge?
Text Compare & Merge is a two-panel diff tool that shows exactly what changed between any two pieces of text. Paste your original on the left, your modified version on the right, and the differences are highlighted instantly — line by line and, for modified lines, word by word.
Beyond just viewing differences, the Merge tab lets you resolve each conflict by choosing which version to keep — the original, the modified, or both. The final merged text is built automatically as you make decisions, ready to copy or download the moment all conflicts are resolved.
Three colour codes tell the story at a glance: red for removed content, green for added content, and amber for lines that exist in both versions but have been edited.
📝 How to Use
🔍 Comparing texts
- Paste your original text in the Original panel
- Paste the modified text in the Modified panel
- Differences appear automatically — no button needed
- Changed lines show red (deleted), green (inserted), or amber (modified)
- Word-level highlights show the exact characters that changed
- Use ← → or Ctrl+↑↓ to jump between changes
- Switch between Split and Unified views
🔀 Merging changes
- Click the Merge tab in the output panel
- Each conflict block shows the original and modified sides
- Click ← Original, Modified →, or Both to resolve
- Use Accept all original or Accept all modified for bulk resolution
- Watch the merged result update in real time
- Click Copy or Download to export
🛍️ Common Use Cases
💻 Code Review
Spot exactly what changed between two versions of a function, config file, or script — without needing a Git repository.
📄 Document Revision
Compare draft versions of contracts, reports, or articles. See every word that was added, removed, or reworded.
🔧 Config & Infrastructure
Diff server configs, environment files, or Kubernetes manifests before deploying to catch unintended changes.
🌍 Translation QA
Compare source and translated strings to verify completeness, or compare two translation files to find inconsistencies.
🗃️ Data & CSV Validation
Compare CSV exports, JSON responses, or SQL query results to validate that a migration or update produced the expected changes.
📝 Content Management
Review edits made to blog posts, product descriptions, or legal copy. Merge the best parts of multiple revisions into a final version.
⚙️ How the Comparison Works
The tool uses a Longest Common Subsequence (LCS) algorithm — the same mathematical foundation used by Git, GNU diff, and most professional diff tools. It finds the optimal edit sequence between the two texts, minimising the total number of insertions and deletions.
| Colour | Meaning | Detail |
|---|---|---|
| Red | Deleted | Present in original, absent in modified |
| Green | Inserted | Absent in original, present in modified |
| Amber | Modified | Present in both but with different content |
| None | Unchanged | Identical in both versions |
What is word-level diff? ▼
For lines that exist in both versions but differ (amber rows), the tool runs a second LCS pass on the individual tokens (words and punctuation) of each line. This reveals the precise sub-word changes with darker highlights inside the amber line. The word diff can be disabled in Options if you prefer a simpler view.
🔒 Privacy & Security
All comparison logic runs entirely in your browser. Your text is never uploaded, transmitted, or stored anywhere. ToolZone itself does not track or collect your data. You can safely compare confidential source code, private documents, API keys, or any sensitive content.
❓ Frequently Asked Questions
What is the difference between Text Compare and a diff checker? ▼
They are the same concept — 'compare text' and 'diff' both mean highlighting what changed between two versions. This tool does both, plus adds word-level highlighting within changed lines and a full merge editor so you can combine the two versions exactly as you need.
How does word-level diff work? ▼
When a line is modified (it exists in both versions but has different content), the tool highlights the exact words that changed within that line rather than marking the whole line as changed. This makes it much easier to spot small edits in long lines.
What does the Merge tab do? ▼
The Merge tab shows every changed block with three resolution buttons: Accept Original (keep the left side), Accept Modified (keep the right side), or Accept Both (include both versions one after the other). Once you resolve all conflicts, the final merged text appears at the bottom ready to copy or download.
Can I ignore whitespace or case differences? ▼
Yes. Open the Options panel to enable 'Ignore case' (so 'Hello' and 'hello' count as identical) and 'Ignore whitespace' (so differences in spaces and indentation are ignored). The original text is still shown — only the comparison logic changes.
How do I load a file instead of pasting text? ▼
Click the Load button above each text panel. Any plain-text file can be loaded — .txt, .md, .json, .csv, .xml, .html, .js, .ts, .py, and so on. The file contents appear instantly in the panel.
What is the maximum text size supported? ▼
The comparison algorithm supports up to 3,000 lines per side comfortably. For very large files beyond that, the tool falls back to a simpler comparison that still shows all differences but may group them differently. Most real-world use cases (code files, config files, documents) are well within the limit.
Are my texts sent anywhere? ▼
No. All comparison logic runs entirely in your browser. Your text never leaves your device. This means you can safely compare confidential documents, source code, API keys, or any sensitive content.
How do I navigate between changes quickly? ▼
Use the ‹ and › arrow buttons in the output header, or the keyboard shortcuts Ctrl+↓ (next change) and Ctrl+↑ (previous change). The view scrolls automatically to the selected change.