Open an MD file: a Markdown viewer in your browser

See a Markdown file (.md) the way it was meant to look, with headings, tables, code, formulas and diagrams, instead of a wall of symbols. Works on a PC, Mac, iPhone or Android phone; the file is read on your device and never uploaded.

Drop your .md file here, or a folder or ZIP of them

Your file stays on this device: it is read here, in your browser, and never uploaded.

Markdown (.md, .markdown), Mermaid (.mmd), a folder, a ZIP or an Obsidian vault. Up to 20 MB per Markdown file.

How it works

Drop the .md file
Or a whole folder, a ZIP or an Obsidian vault, or paste the text. It is read by code running in this page; nothing is sent anywhere.
Read it formatted
Headings, lists, tables, code with colors, math formulas and Mermaid diagrams are drawn as they should be. Find words, jump through the contents, or switch to the source.
Save or share it
Save the file as a PDF or a Word document, print it, or copy it as formatted text into Word, Google Docs or an email. Converting a whole folder in one go is paid.

Markdown files, explained

What an .md file is

An .md file is a Markdown document: plain text in which a few symbols stand for formatting. A line starting with # is a heading, words between ** are bold, a line starting with - is a list item, text between backticks is code, and rows separated by | are a table. Programs that understand Markdown show the formatting; everything else shows the symbols.

Markdown is the format of README files on GitHub, of notes in apps such as Obsidian, of documentation, and increasingly of text written by AI assistants: ChatGPT, Claude and coding tools such as Cursor hand out answers, reports and plans as .md files. The extension may also be .markdown, and Mermaid diagrams are often saved as .mmd. A whole ChatGPT or Claude chat history comes as a data export instead: open it with the chat export viewer.

Why it opens as plain text, or not at all

macOS has no Markdown viewer, and Windows has only a basic one: Notepad in current Windows 11 shows headings, bold, italic, lists and links, but not code colors, formulas or diagrams, and older Windows has none. Double-clicking an .md file either asks which program to use or opens it in a text editor such as Notepad or TextEdit, which shows the raw symbols or only part of the formatting. On an iPhone or iPad, the Files app shows the plain text too, and an email attachment ending in .md often cannot be previewed at all.

What this viewer does

Shows Markdown in GitHub’s flavor (CommonMark plus GitHub’s tables, task lists, strikethrough and automatic links), with footnotes and a table of contents built from the headings.
Colors code blocks in common programming languages, and sets math formulas written between $…$, $$…$$, $…$ or \[…\], the way ChatGPT writes them.
Draws Mermaid diagrams (flowcharts, sequence, class, state, Gantt, pie charts and more) from ```mermaid blocks and .mmd files.
Opens a folder, a ZIP or an Obsidian vault: every note in a list, pictures next to the notes shown in place, ![[picture.png]] embeds found anywhere in the vault.
Finds words in the document, shows the source, and prints.
Saves the open file as a PDF (with bookmarks for the headings and working links) or a Word document (.docx, with Word’s heading styles), or copies it as formatted text for Word, Google Docs or an email. Those are free; converting a whole folder in one go is paid. More on these outputs: Markdown to PDF and Word.

Safe to open, even from a stranger

A Markdown file can contain HTML, links and references to pictures on the web, and some of that could be used to run code or to tell the sender that the file was opened. Here the document is cleaned before it is shown and displayed in an isolated frame where no script can run. Links open in a new tab. Pictures from the web are not loaded until you choose “Load pictures”, and diagrams are drawn in a separate sandbox that cannot reach the page.

What it does not do

It does not edit the file: it is a viewer and a converter.
It does not run code blocks, embedded scripts or HTML forms.
It does not load pictures from the web unless you ask, and it never puts them into a PDF or Word file (Print keeps them).

Other ways to open an .md file

Visual Studio Code (free, Windows, Mac, Linux): open the file and press Ctrl+Shift+V (Cmd+Shift+V on a Mac) for its preview.
Obsidian or Typora: Markdown editors that show the formatting while you write.
GitHub: an .md file in a repository is shown formatted on its page.
Any text editor shows the text itself; Markdown was designed to stay readable that way.

Your file stays on your device

Notes, reports and AI drafts are often private. Here the file is read by code running in your browser; no code on the page sends the file, its name or anything in it anywhere, not even to our own domain. The one exception is yours to make: if you choose “Load pictures”, your browser fetches the web pictures the file names from their own sites. PDFs and Word files are made in the page too.

Microsoft, Windows, Word and Visual Studio Code are trademarks of Microsoft Corporation; Google Docs is a trademark of Google LLC; ChatGPT is a trademark of OpenAI; Claude is a trademark of Anthropic; Obsidian, Cursor, GitHub and Typora are trademarks of their owners. CantOpen is not affiliated with or endorsed by any of them.

Frequently asked questions

How do I open an MD file?

Drop it on this page: it appears formatted right away, in any modern browser on Windows, Mac, Linux, iPhone, iPad or Android, with nothing to install. You can also paste the text.

What program opens .md files on Windows?

Notepad in current Windows 11 shows basic Markdown formatting (headings, bold, lists and links); code colors, formulas and Mermaid diagrams stay as text, and older Windows versions open the file as plain text or ask for a program. This page shows all of it formatted without installing anything; Visual Studio Code, Obsidian and Typora are programs that also do.

Is it free?

Yes: opening and reading every file, find, print, and saving one file at a time as PDF or Word are free, with no account. Converting a whole folder, ZIP or vault in one go is the paid part.

Is my file uploaded?

No. It is read by code running in your browser and never leaves your device. No code on the page sends the file, its name or its contents anywhere, not even to our own domain. Pictures from the web in the file load only if you choose “Load pictures”.

ChatGPT gave me an .md file. How do I read it?

Drop it here. Headings, bullet points, tables, code and formulas appear as ChatGPT meant them, and you can save the result as a PDF or a Word document, or copy it into an email or Google Docs with the formatting.

Does it show Mermaid diagrams and math formulas?

Yes. Mermaid diagrams in ```mermaid blocks (and .mmd files) are drawn, and formulas in $…$, $$…$$, $…$ and \[…\] are set with KaTeX. In a PDF or Word file both become pictures.

Can I open a whole Obsidian vault?

Yes: drop the vault folder or a ZIP of it. Every note is listed, pictures and ![[embeds]] are found in the vault, and [[links]] are shown. Converting the whole vault to PDF or Word files in one go is paid.