Free Text Diff Tool
Updated September 2026
Compare two texts side by side and highlight line-by-line differences — additions in green, deletions in red. Free online line diff tool.
Verified Capabilities
Compares two texts line by line and shows exactly which lines were added or removed.
A summary line above the diff reports the total lines added and removed.
All comparison runs in your browser — no text is uploaded to any server.
Line-diff only — no word-diff mode or toggle, no navigation arrows between changes, and no copy/unified-diff export button.
Writing, development, and content work all involve repetitive text tasks. The Text Diff Checker automates this instantly so you can focus on what actually matters.
Compare two texts side by side and highlight line-by-line differences — additions in green, deletions in red. Free online line diff tool. Results are immediate — no waiting, no loading screens, no account required.
Who uses the Text Diff Checker?
- Writers comparing original and edited manuscript versions to track revision changes.
- Developers reviewing configuration file changes before deploying to production.
- Legal professionals comparing contract versions to spot modifications between drafts.
Common uses and search terms
The Text Diff Checker is frequently used for: text diff, compare text, text comparison, line diff. Whether you need a quick result or are working through a longer project, the tool handles all common variations without any configuration.
Why use Allio Tools's Text Diff Checker?
Everything runs locally in your browser. No data is sent to a server, logged, or stored anywhere. The tool is completely free with no usage limits, no premium tiers, and no account required. Available in 11 languages and optimised for all screen sizes, the Text Diff Checker works on desktop, tablet, and mobile with no app download needed.
See also:Word Unscrambler · Word Counter · Synonym Finder
How the Text Diff Checker works
Paste the original text in the left panel and the revised text in the right panel.
Click Compare to see a line-by-line diff with additions in green and deletions in red.
The summary above the diff shows how many lines were added and removed.
Tips & tricks
- This tool only does line-level diffing — there's no word-diff mode, no mode toggle, and no inline highlighting of the specific word that changed within a modified line.
- There's no navigation arrows to jump between changes and no copy/export button — scroll through the result manually and select text to copy if you need it.
- A line that has any character changed (even one letter) shows up as a full removed line plus a full added line, not a highlighted partial change — this is normal LCS line-diff behavior, not a bug.
Frequently Asked Questions
What is a text diff and how does it work?
A diff algorithm compares two texts and identifies the minimum set of additions and deletions needed to transform one into the other. This tool uses a line-based LCS (longest common subsequence) algorithm — the same general family of technique Git uses to show code changes, applied here at the line level.
Can I compare code files, not just plain text?
Yes. The tool handles any text including code, HTML, JSON, SQL, and markdown. There's no syntax highlighting — content is compared and displayed as plain monospace text regardless of programming language.
Does this tool have a word-diff mode, separate from line diff?
No — there's only one mode: line-by-line comparison. A line is either shown unchanged, marked as added, or marked as removed; there's no inline word-level highlighting within a changed line, and no mode toggle to switch to one.
Can I copy the diff result or export it as a unified diff?
No — there's no copy button and no unified-diff export. The colored diff is for on-screen viewing only; select and copy the text manually if you need it elsewhere.
Is my text stored or sent to a server?
No. All comparison is done entirely in your browser. No text is transmitted or stored anywhere.
Can I compare more than two versions?
The tool compares exactly two inputs at a time. For multi-version comparison, run multiple paired comparisons (v1 vs v2, then v2 vs v3).
Is my data safe when using the Text Diff Checker?
Completely safe. The Text Diff Checker processes everything locally in your browser. No input data, results, or usage information is ever transmitted to or stored on any server.
Is there a character or word limit for the Text Diff Checker?
The Text Diff Checker has no hard character limit — it processes text as large as your browser can handle, typically hundreds of thousands of characters. Very large inputs may be slower depending on your device.
Can the Text Diff Checker process text in other languages?
Yes. The Text Diff Checker handles all Unicode text correctly, including accented characters, CJK characters, Arabic, Cyrillic, and emoji. It works with any language that your browser renders, with no additional setup or language packs required.
Works with ChatGPT, Claude, Cursor, GitHub Copilot, VS Code, Poe and more — 106+ tools, zero data collection.