Heading-aware
The outline names headings that arrived, left, or changed level, using the same Markdown engine as preview.
Diff
Compare two Markdown files in this browserMarkdown diff checker
Drop the original and the revised .md file. MD Viewer compares them locally and shows heading-aware changes.
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Drop or paste the older Markdown file on the left.
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Drop or paste the candidate on the right. You can also drop both files at once.
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Use Outline for section changes, Source for the line walk, and Preview to see both documents.
The outline names headings that arrived, left, or changed level, using the same Markdown engine as preview.
Both files are read in this browser. Originals on disk are not overwritten.
Keep a unified .diff if you need a record. Line endings that differ are called out without rewriting every line.
Questions
No. Both files are read in this browser. MD Viewer does not send the source to a server.
The outline names headings that were added, removed, or changed level, using the same Markdown profile as preview. The source view still shows every changed line.
No. Opening a file for comparison does not write back to disk. Download a unified .diff if you want a record to keep.
It is a local two-file comparison, not a repository tool. It does not need Git, and it names Markdown headings instead of only listing line numbers.