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Text Compare: Find the Difference Between Two Texts Online

A text compare tool shows the difference between two pieces of text by marking what was added, what was removed and what stayed the same. Paste the original on the left and the changed version on the right, click Compare, and the tool highlights changes in side-by-side or unified view, down to the word or character. Everything runs in your browser.

Compare two texts now or read on to learn how to read a diff, what the similarity score really measures and when to trust the result.

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Quick start

1Paste the original text

2Paste the changed text

3Choose a view

4Set options

Diff Editor

Paste text to compare

Original Original / Left

0 lines / 0 chars

Modified Modified / Right

0 lines / 0 chars

↔

Paste text in both panels above and click Compare to see the diff.
Supports code, prose, config files, JSON, YAML, and any plain text.

`; const blob = new Blob([html], { type: 'text/html' }); const a = document.createElement('a'); a.href = URL.createObjectURL(blob); a.download = 'diff-export.html'; a.click(); showToast('HTML exported'); } function exportPatch() { if (!diffData.length) { showToast('Run compare first'); return; } let patch = '--- original\n+++ modified\n@@ -1 +1 @@\n'; for (const r of diffData) { if (r.type === 'same') patch += ' ' + (r.left ?? '') + '\n'; else if (r.type === 'del') patch += '-' + (r.left ?? '') + '\n'; else if (r.type === 'add') patch += '+' + (r.right ?? '') + '\n'; else if (r.type === 'mod') { patch += '-' + (r.left ?? '') + '\n'; patch += '+' + (r.right ?? '') + '\n'; } } const blob = new Blob([patch], { type: 'text/plain' }); const a = document.createElement('a'); a.href = URL.createObjectURL(blob); a.download = 'diff.patch'; a.click(); showToast('Patch exported'); } function copyDiff() { if (!diffData.length) { showToast('Run compare first'); return; } let text = ''; for (const r of diffData) { if (r.type === 'same') text += ' ' + (r.left ?? '') + '\n'; else if (r.type === 'del') text += '- ' + (r.left ?? '') + '\n'; else if (r.type === 'add') text += '+ ' + (r.right ?? '') + '\n'; else if (r.type === 'mod') { text += '- ' + (r.left ?? '') + '\n'; text += '+ ' + (r.right ?? '') + '\n'; } } navigator.clipboard.writeText(text).then(() => showToast('Diff copied to clipboard')); } /* ================================================================ TOAST ================================================================ */ function showToast(msg) { const t = document.getElementById('wbToast'); t.textContent = msg; t.classList.add('show'); setTimeout(() => t.classList.remove('show'), 2200); } /* ================================================================ FAQ ================================================================ */ (function() { document.querySelectorAll('#wbFaq .wb-faq-item').forEach(function(item) { item.querySelector('.wb-faq-q').addEventListener('click', function() { const open = item.classList.contains('open'); document.querySelectorAll('#wbFaq .wb-faq-item').forEach(i => i.classList.remove('open')); if (!open) item.classList.add('open'); }); }); })();

Quick answer:: Input:

an original text and a modified text. Output: added, removed and unchanged lines, with optional word-level and character-level highlights. Views: side by side or unified (+ and - lines). Similarity score: unchanged lines divided by the larger line count, as a percentage.

What Is a Text Compare Tool?

A text compare tool, also called a diff checker, text diff or text difference checker, compares two versions of a text and shows exactly what changed. It lists lines that were added, lines that were removed and lines that stayed the same.

The word "diff" comes from the Unix diff command, which dates from the early 1970s and was included in Unix in 1974. Today the same idea powers code review on GitHub, document tracking and configuration checks.

Developers use it to review code. Writers use it to compare drafts. QA engineers use it to verify edits. System administrators use it to compare configuration files between environments.

How to Use the Text Compare Tool

1
STEP 1 Paste the original text into the left panel, labelled Original. You can also use Upload to load a text file.
2
STEP 2 Paste the changed text into the right panel, labelled Modified.
3
STEP 3 Choose a view: Side by Side or Unified.
4
STEP 4 Set options: Ignore case, Ignore whitespace, Ignore blank lines, Word-level diff, Char-level diff and Fold unchanged.
5
STEP 5 Click Compare. The differences appear below with colour coding and a similarity score.
6
STEP 6 Move through the changes and export the diff as HTML or patch format if you need to share it.
7
STEP 7 Use Swap to flip the two sides, or Clear All to start again.

Expert tip

Use the Load Code Example, Load Prose Example or Load Config Example buttons first to see how additions, removals and word-level highlights look. Then paste your own text.

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How to Read the Results

What you see	Meaning	Typical colour
Added line	Exists only in the modified text	Green
Removed line	Exists only in the original text	Red
Unchanged line	Same in both texts	No highlight (can be folded)
Changed line with word highlights	Line differs, with the changed words marked inside it	Red strikethrough for the old word, green for the new word
Character highlights	Exact letters that differ inside a changed word	Useful for typos and punctuation

Turn on Fold unchanged for long texts so you only see the changed areas and a little context around them.

Side by Side or Unified View?

Feature	Side by side	Unified
Layout	Two columns: original left, modified right	One column with + and - prefixes
Best for	Small to medium changes and visual comparison	Large files, patches and Git-style output
Alignment	Matching lines sit next to each other	Removed lines appear before added lines
Common in	IDEs and code review tools such as VS Code and GitHub	Git patch files and email patches
Space	Needs a wider screen	Compact

On a phone or narrow window, the unified view is easier to read.

Word-Level and Character-Level Diff

Line-level only: a whole line is marked changed even when one word differs. This can bury a small edit in a long paragraph.
Word-level diff: inside a changed line, only the added or removed words are highlighted. This is the best setting for prose.
Character-level diff: inside a changed word, the exact characters that differ are marked. This catches typos, a changed digit or a missing punctuation mark.

Ignore Case, Whitespace and Blank Lines

The three ignore options remove noise. Ignore case treats Apple and apple as equal. Ignore whitespace skips differences in spaces and tabs, which helps when code was re-indented. Ignore blank lines skips empty lines that were added or removed. Turn them on when formatting changes hide the real edits. Turn them off when you need to find those formatting changes, for example in a YAML file where indentation matters.

What Is the Myers Diff Algorithm?

The Myers diff algorithm was published by Eugene Myers in 1986 in the paper "An O(ND) Difference Algorithm and Its Variations". Git and GNU diff use it as their standard algorithm, and so do many diff tools, including the live tool. It finds the shortest edit script, meaning the smallest number of insertions and deletions needed to turn one text into the other.

Its running time is O(ND), where N is the combined length of the two sequences and D is the number of differences. When the texts are similar, D is small, so the tool stays fast even for big files. In plain terms: the fewer changes there are, the faster the comparison.

A shortest edit script is not always the one a human finds clearest. Some tools offer other strategies, such as patience diff, that favour more readable output. Myers aims for the smallest set of edits.

What Does the Similarity Score Mean?

The similarity score is a percentage from 0 to 100 shown after you compare. The live tool calculates it as unchanged lines divided by the larger of the two line counts, multiplied by 100. A score of 100% means the texts are identical. A score of 0% means they share no common lines.

How to read it correctly

The score counts lines, not words or characters.

If a text is one long line, any change makes that line different, so a single edited word can give 0%.

If a document has 100 lines and 90 are unchanged, the score is 90%, even if the other 10 lines were completely rewritten.

It is a quick measure of how much a document changed. It is not a plagiarism, quality or meaning score.

For prose, put each sentence on its own line before comparing so the score reflects sentence-level changes more fairly.

Text Compare Use Cases

Code review

Compare a function before and after refactoring without setting up Git.

Document revisions

See what changed between a first draft and a final contract, specification or article.

Configuration management

Compare .env, YAML or JSON settings between staging and production.

Content QA

Check an editor's changes against the brief before publishing.

Data checks

Compare query output from two runs. Tidy JSON first with the JSON formatter so both sides use the same layout.

Translation checks

Compare structure and line count between a source and a translated document.

Log analysis

Find new error patterns between two deployments.

SEO files

Compare two versions of a robots.txt file, then validate the final one with the robots.txt generator and validator.

Text Compare vs Other Ways to Diff

Method	Good at	Trade-off
This online tool	Quick checks with no setup, word and character highlights	Plain text only, one pair at a time
Word or Google Docs compare	Tracked changes in formatted documents	Needs a word processor and both files in that format
VS Code compare	Comparing files in a project	Needs the editor installed
git diff	Version-controlled code	Needs a repository and the command line

Common Mistakes

Reading the similarity score as quality or plagiarism. It is a line-based percentage.
Comparing pasted text with different line wrapping. One side wrapped at 80 characters and the other not will look entirely different.
Leaving ignore options on by mistake. Ignored whitespace can hide a real change in a YAML or Python file.
Swapping sides without noticing. Added and removed are reversed, so check which text is Original.
Comparing formatted documents. Copy plain text first, because bold, tables and images are not compared.
Expecting moved blocks to be recognised. A paragraph moved to a new place shows as a removal and an addition.

Limits of This Tool

It compares plain text. Formatting, images and comments inside Word or PDF files are not compared. Upload accepts text files. Confirm the allowed types on the live tool.
The diff is by lines, with word and character detail added inside changed lines.
The similarity score is only a line-based percentage.
It compares two texts at a time, not three-way merges.
A diff shows what changed, not whether the change is correct.

Privacy

The live page states that all diff processing runs in your browser and that neither panel's content is sent to a server, logged or stored. That makes it suitable for private code, contracts and documents. As a habit, remove API keys and passwords from text before you paste it into any online tool, even one that runs locally.

Open the tool

Frequently Asked Questions

What is a text compare tool?

It compares two versions of a text and highlights what was added, removed or left unchanged. It is also called a diff checker or text difference checker.

How do I compare two texts online?

Paste the original text on the left and the modified text on the right, then click Compare. The differences appear with colours and a similarity score. Use Word-level diff to mark changed words inside lines.

What is the Myers diff algorithm?

It is the algorithm published by Eugene Myers in 1986 that finds the shortest set of insertions and deletions turning one text into another. Git, GNU diff and this tool use it.

What does the similarity score mean?

It is unchanged lines divided by the larger line count of the two texts, times 100. A score of 100% means identical text and 0% means no common lines. It counts lines, not words.

Why is my similarity score 0% when I only changed one word?

Because the score is line-based. If your text is a single long line, changing one word changes the whole line, so no lines match. Put each sentence on its own line to get a more useful score.

What is the difference between side by side and unified view?

Side by side shows the original on the left and the modified text on the right. Unified shows one column with minus lines for removals and plus lines for additions, as in a Git patch.

Can I ignore whitespace or case?

Yes. Use the Ignore case, Ignore whitespace and Ignore blank lines options to hide those differences and focus on real edits.

Can I compare code?

Yes. It works with code, configuration files, JSON, YAML and any plain text, and the Char-level diff option helps catch small changes in variable names.

Is my text sent to a server?

No. The live page states the comparison runs in your browser and nothing is sent to a server, logged or stored.

Can I save or share the result?

Yes. You can export the diff as HTML or in patch format, according to the live page. Compare your texts Need to check how long your two versions are? Use the word counter. To clean a list before comparing, use the duplicate word remover.

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Text Compare: Find the Difference Between Two Texts Online

Diff Editor

What Is a Text Compare Tool?

How to Use the Text Compare Tool

How to Read the Results

Side by Side or Unified View?

Word-Level and Character-Level Diff

Ignore Case, Whitespace and Blank Lines

What Is the Myers Diff Algorithm?

What Does the Similarity Score Mean?

Text Compare Use Cases

Code review

Document revisions

Configuration management

Content QA

Data checks

Translation checks

Log analysis

SEO files

Text Compare vs Other Ways to Diff

Common Mistakes

Limits of This Tool

Privacy

Frequently Asked Questions

What is a text compare tool?

How do I compare two texts online?

What is the Myers diff algorithm?

What does the similarity score mean?

Why is my similarity score 0% when I only changed one word?

What is the difference between side by side and unified view?

Can I ignore whitespace or case?

Can I compare code?

Is my text sent to a server?

Can I save or share the result?

Ready to try the Text Compare?

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