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Text Compare & Diff Checker

Paste two texts and instantly see every difference — line by line, word by word, or character by character.

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Frequently Asked Questions

How does the text compare tool work?+
Paste your original text and modified text into the two editors, then click Compare. The tool runs a diff algorithm (similar to Git's diff) directly in your browser to find insertions, deletions, and unchanged sections. Results are color-coded: green for additions, red for removals, and gray for unchanged content.
What is the difference between line, word, and character diff modes?+
Line-by-line mode compares whole lines and is best for code or structured text. Word-by-word mode highlights individual changed words within paragraphs — ideal for proofreading prose. Character-by-character mode shows the most granular changes, useful for spotting typos or single-character edits like variable names.
Is my text uploaded to a server?+
No. All text comparison happens entirely in your browser using JavaScript. Your text never leaves your device, so it is completely private and safe for confidential documents, code, or personal notes.
Can I compare code files with this tool?+
Yes. The line-by-line diff mode works exactly like the diff view in Git or VS Code. Paste any code — JavaScript, Python, HTML, CSS, JSON, or any other language — and the tool will highlight added, removed, and modified lines with inline word-level highlighting for changed lines.
What does the similarity percentage mean?+
The similarity percentage shows how much of the original text remained unchanged. A 100% similarity means both texts are identical. A 0% similarity means every line was changed. It is calculated as the ratio of unchanged lines to the total number of lines in the longer document.
Is there a size limit for text comparison?+
There is no hard limit since everything runs locally, but very large texts (over 100,000 lines) may take a moment to process. For most use cases — documents, code files, articles — the diff completes instantly.

How to Compare Two Texts Online

A text compare tool (also called a diff checker) is the fastest way to spot differences between two versions of a document, code file, or any block of text. Whether you're reviewing a colleague's edits, debugging config changes, or tracking revisions in a legal contract, a side-by-side diff view makes every insertion, deletion, and modification instantly visible. Here's how to use this tool:

  1. 1Paste your original text. Copy the first version — the baseline — into the left editor. This can be code, prose, CSV data, or any plain text.
  2. 2Paste the modified text. Drop the second version into the right editor. The tool accepts any length — from a single sentence to thousands of lines of code.
  3. 3Choose a diff mode. Pick Line for code and structured text, Word for proofreading paragraphs, or Character for the most granular comparison.
  4. 4Click Compare. The diff result appears below with additions highlighted in green, removals in red, and unchanged content in gray. The summary bar shows total lines added, removed, unchanged, and overall similarity.
  5. 5Copy or share. Hit the Copy Diff button to grab a plaintext version of the diff for pasting into pull requests, code reviews, or documentation.

When to Use a Text Compare Tool

💻 Code Reviews

Compare two versions of a source file to spot exactly what changed — perfect when you don't have access to Git or a dedicated IDE. Works with JavaScript, Python, HTML, CSS, JSON, YAML, and any plain text format.

✍️ Writing & Editing

Track an editor's revisions by comparing drafts side by side. The word-level diff makes it easy to accept or reject individual changes in blog posts, articles, or marketing copy.

⚙️ Configuration Auditing

Diff server configs, .env files, or infrastructure-as-code templates before deploying. Catch unintended changes to environment variables, ports, or API keys in seconds.

📜 Legal & Compliance

Compare contract revisions, terms of service updates, or policy documents. The character-level diff ensures no clause or comma slips through unnoticed — critical for regulated industries.

How the Diff Algorithm Works

This text compare tool uses a Longest Common Subsequence (LCS) algorithm — the same mathematical foundation behind git diff. It finds the longest sequence of tokens (lines, words, or characters) that appear in both texts in the same order, then marks everything outside that sequence as either an addition or a removal.

In line mode, the tool goes one step further: when an original line is removed and a new line is added at the same position, it treats them as a modified pair and runs a secondary word-level diff to show exactly which words changed within that line. This gives you the precision of a character diff with the readability of a line diff.

For very large inputs (over 5,000 characters in character mode), the tool switches to a Myers diff algorithm for better performance. Myers diff computes the shortest edit script in O(ND) time, where N is the total length and D is the number of differences — making it blazing fast when the texts are mostly similar.

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