Markdown Diff Checker

Compare Markdown files in five steps

1. Paste the original Markdown into Before and the revised Markdown into After.
2. Choose Upload original Markdown or Upload modified Markdown for a .md, .markdown, or .txt file.
3. Open Block diff to compare parsed blocks and changed words inside paired blocks.
4. Open Source diff to compare the raw Markdown lines.
5. Open Rendered preview to inspect the separate Before and After renderings with change highlights.

What a Markdown block diff shows

Each heading, paragraph, list item, fenced code block, blockquote, table, or horizontal rule becomes one comparison unit. When a removed block and an added block have the same type, Block diff pairs them as a modified block. A block with no pair appears as added or removed.

Before:
- Fix login

After:
- Fix sign-in

Block diff pairs these list items and marks the changed words. Similarity is the percentage of unchanged pairs among all paired results. The result area reports Blocks added, Blocks removed, Blocks modified, and Blocks unchanged.

How whitespace options change Markdown comparison

Ignore trailing whitespace and Collapse multiple spaces are checked when the page opens. The first removes spaces and tabs at line ends before block matching. The second changes each run of spaces or tabs into one space.

Before: Title   text
After:  Title text

With Collapse multiple spaces checked, these lines match in Block diff. Ignore blank-line differences starts unchecked. When checked, it compresses every whitespace run into one space before matching. All three controls affect block matching only. Source diff always compares the raw lines.

Which Markdown syntax the comparison reads

The parser reads hash headings and underlined headings, list items marked with -, *, +, or a number followed by . or ), fenced code with matching backticks or tildes, pipe tables with a delimiter row, blockquotes, horizontal rules, and ordinary paragraphs. Empty lines separate blocks.

Rendered preview supports headings, paragraphs, lists, fenced code, blockquotes, tables, horizontal rules, inline code, italics, and links. The inline formatter removes bold markers and turns supported single-marker emphasis into italics. It escapes source text as HTML before formatting. Link URLs beginning with javascript:, data:, or vbscript: become #. Other Markdown can remain plain text or render differently.

Both panels need non-whitespace content before results appear. Block pairing can change when the document structure changes. Tables stay together as whole blocks, and raw HTML is escaped rather than passed through as markup.

Where Markdown diffs come up

For a README revision, compare the two versions in Block diff, then check Rendered preview for changes to headings, lists, and links.

For release notes with a table or fenced command example, use Source diff to inspect the exact Markdown lines.

For a generated Markdown report, the block counts show how many blocks were added, removed, modified, or left unchanged.

When to use Markdown Diff Checker

Open Compare Tools when the input format is unclear. Choose Compare Text for plain prose and character, word, or line differences. Choose HTML Diff Checker for HTML source with rendered previews, or Code Diff Checker for code with syntax highlighting, line numbers, and patch copying.

Frequently asked questions