Compare two Markdown documents side-by-side. See every addition and deletion.
Free Markdown Diff Tool compares two Markdown documents line-by-line using a classic LCS algorithm and shows every addition, deletion, and unchanged line. View results side-by-side for visual review or unified-diff style for copy-paste into a PR description or bug report.
Privacy: This tool runs entirely in your browser. Your text is never uploaded, logged, or cached. Close the tab and it's gone. Verify in DevTools → Network: zero requests fire.
Running a visual diff shouldn't require a desktop app or a paid SaaS. The diff runs entirely in your browser.
| Input | Output | Typical size | Speed | Login needed |
|---|---|---|---|---|
| Two Markdown documents | Line-level diff (visual + unified text) | Up to ~5,000 lines per side | < 100 ms typical | No |
Here's what this free tool does in detail — every feature is built to solve real problems, runs entirely in your browser, and is free forever.
Toggle between Side-by-side (left/right columns with synchronized line numbers) and Unified (git-style +/- output). Side-by-side is best for visual review; unified is perfect for pasting into a PR description, an issue comment, or a runbook.
For markdown formatting cleanup instead of comparison, use the Free Markdown Formatter.
The tool uses a longest-common-subsequence diff, the same family of algorithms behind git diff and diff -u. It's deterministic, handles arbitrary line order, and produces the minimal set of edits (fewest total changes) to turn the original into the modified version.
Above the diff view, see a live count of added, removed, and unchanged lines. Useful for summarizing the scope of a change in a PR description ('18 added, 6 removed') without manually counting.
Both documents are processed entirely in your browser — verify in DevTools → Network that zero requests fire. The diff runs in a plain JavaScript function in your tab. Neither the original nor the modified document ever touches our servers.
Paste the 'before' version into the left pane.
Paste the 'after' version into the right pane.
Use side-by-side for visual review or switch to unified view to copy the diff text.
See exactly what changed between two drafts of a blog post or article.
Compare two versions of a doc to summarize updates for a release note.
Review edits from a collaborator without waiting for a git-based workflow.
Diff two test plan documents to find what coverage was added or removed.
Compare two essay drafts to measure progress on revisions.
Yes. Free forever, no account required.
Classic longest-common-subsequence (LCS) — the same family as git diff.
No — it does a pure line-level diff. For most editing workflows this is exactly what you want. Semantic-aware diffing (e.g. comparing headings vs paragraphs) is a different algorithm.
Up to ~5,000 lines per side runs in milliseconds. Larger documents will still work but may take a second or two.
No. Both documents are processed 100% in your browser.