.md file format
Preview, inspect, merge, clean, and learn how Markdown files are used for documentation, notes, README files, static sites, writing, developer workflows, and content publishing.
Also known as: MD
Format
.md
Original files stay unchanged. Tools download a new file when output is generated.
Every tool listed here works with .md files and runs in your browser. If the task you need is not here, the related formats below may cover it.
Preview Markdown files and inspect raw Markdown text side by side.
Merge Markdown files in order with clean spacing between each document.
Open, search, and inspect plain text files in your browser.
Merge plain text files in your chosen order with clean spacing between files.
Clean common OCR mistakes from copied scans and extracted document text.
The original 2004 syntax left many cases undefined, so implementations diverged. CommonMark pinned down the ambiguities; GitHub Flavored Markdown adds tables, task lists, strikethrough, and autolinking on top. A document that renders correctly in one tool can render differently or not at all in another, and tables are the usual casualty.
Raw HTML is permitted by the specification but stripped by many renderers for safety. Footnotes, definition lists, math blocks, and admonition callouts are extensions rather than standard syntax. YAML front matter between triple-hyphen markers at the top of a file is a static-site convention, not part of Markdown, and appears as literal text in renderers that do not know about it.
Most Markdown problems are visible only by comparing the two. A list that will not nest is usually an indentation depth issue; a fenced code block that swallows the rest of the document is an unclosed fence; a table that renders as a paragraph is a missing separator row. Seeing source and output side by side finds these faster than fixing them blind.
A table needs a separator row of hyphens between the header and the body, and the renderer has to support tables at all — tables are a GitHub Flavored Markdown extension, not core syntax.
The specification allows it, but many renderers strip HTML for security. Do not rely on it for anything that must display consistently.
A metadata block, usually YAML between triple-hyphen lines, used by static site generators for things like title and date. It is a convention of those tools rather than part of Markdown.
No. Both extensions mean the same thing; .md is simply the common choice.