Compare two blocks of text side by side with differences highlighted in color. This tool identifies additions, deletions, and changes between two versions of any text — code, config files, articles, or patch notes.
Last updated: June 2026
Paste two blocks of text and instantly see every difference highlighted. Added text is shown in green, removed text in red. Perfect for comparing code, documents, and configuration files.
The diff tool compares your two texts line by line and highlights every change. Lines that exist in the first text but not the second are marked as deletions (red). Lines in the second text but not the first are marked as additions (green). Unchanged lines are shown for context. The algorithm finds the longest common subsequence to produce the smallest possible diff.
Comparing two versions of a document to see what changed. Reviewing code changes before committing. Checking differences between configuration files across environments. Verifying that a find-and-replace operation changed only what you intended. Comparing game patch notes to see exactly what the developers changed. Auditing contract revisions between draft versions.
| Use Case | What to Compare | Why |
|---|---|---|
| Code Review | Previous version vs. current version of source code | Catch bugs, verify logic changes, ensure nothing unintended changed |
| Config Changes | Production config vs. staging config | Find mismatches that could cause deployment failures |
| Document Revisions | Draft v1 vs. draft v2 of a contract or proposal | Track every edit between revisions for legal or editorial review |
| Game Patch Notes | Previous patch notes vs. current patch notes | Spot stealth nerfs, undocumented changes, or silent fixes |
| API Response Changes | Expected response vs. actual response | Debug integration issues by finding missing or changed fields |
Diff output uses color coding and symbols to make changes immediately visible. Lines highlighted in green (or prefixed with a "+" symbol) are additions — text that exists in the modified version but not in the original. Lines highlighted in red (or prefixed with a "-" symbol) are deletions — text that was in the original but has been removed. Unchanged lines appear without highlighting and provide context so you can locate exactly where changes occurred. Some diff tools also show modifications within a line: if you changed one word in a sentence, the entire line might appear in both the deleted and added sections, with the specific changed word highlighted differently. Understanding how to read diff output is a foundational skill for software development, technical writing, and any work that involves tracking changes across document versions. The key is to read the red (removed) and green (added) sections together to understand what transformation occurred.
Diffs are the foundation of modern version control systems like Git, Mercurial, and SVN. When you run "git diff" in a repository, Git compares files line by line and produces output showing exactly what changed. Every Git commit internally stores the diff between the previous and current state of each modified file, which is why Git repositories remain relatively small even with thousands of changes — they store diffs, not complete copies. Pull requests on GitHub, GitLab, and Bitbucket display diffs in a user-friendly format so code reviewers can see exactly what a developer changed. The "git blame" command uses diff history to show who last modified each line of code and when. Understanding diffs helps developers write better commit messages (describing what the diff changes) and review code more effectively. Even non-developers benefit from diff literacy when using tools like Google Docs' version history or WordPress' revision comparison.
The way you compare text should differ depending on whether you are comparing code or natural language prose. Code comparisons are line-oriented — even a single space or tab change can be meaningful, so whitespace differences should be visible. Programming languages are case-sensitive, so "Variable" and "variable" are entirely different identifiers. Code diffs typically show changes line by line because the line is the natural unit of code. Prose comparisons, on the other hand, benefit from word-level diffing. If you change one word in a paragraph, a line-level diff shows the entire paragraph as deleted and re-added, which makes it hard to spot the actual change. Word-level diff tools highlight only the specific words that changed, making it much easier to review document edits. When comparing prose, you usually want to ignore whitespace differences, trailing spaces, and sometimes even capitalization changes. This tool uses line-level comparison, which works well for both code and short text blocks.
Currently this tool works with pasted text. Open your files in a text editor, copy the contents, and paste them into the two input areas.
The tool works well for texts up to about 50,000 characters. For very large files (over 1 MB), a desktop diff tool like WinMerge or VS Code's built-in diff viewer may be more practical.
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