# Guide / What is Markdown?
What is a .md file?How to open it, and what to do when it will not
.md is the file extension for plain-text files written in Markdown. People also call them “MD files” or “Markdown files”. They open without any special app, but as they stand you see marks such as # and ** in a row.
What you use depends on whether you just want to see what is inside, or want to read it with headings and tables in shape. Here it is device by device.
Last checked October 4, 2026
# Sales report tool Adds up each month's sales from CSV files and writes them out as a table. ## How to use 1. Put the CSV files in `data/` 2. Run the command below 3. `report.md` is created ```bash python aggregate.py --month 2026-09 ``` ## Options | Option | Default | What it does | | --- | --- | --- | | `--month` | This month | Month to add up | | `--out` | `report.md` | Where to write | ## Notes - [x] Needs Python 3.11 or later - [ ] Keep the files in **UTF-8**
Nothing is saved. What you type is gone when you leave this page.
On this page
What a .md file is (the .md extension)
.md marks a file written in Markdown. It holds nothing but text — no images, no formatting data. Unlike a Word .docx, it is not tied to one particular app.
These days you often receive one as a document made by an AI such as ChatGPT or Claude, or as the README.md that comes with a program.
If you open it and see marks everywhere, nothing is broken. # is a heading, - is a bullet, | is a table: the shape of the document is written with marks. What each mark means is covered in What is Markdown?.
The .md extension, and other names for it
The .md at the end of a file name is its extension: a label saying “this file is written in Markdown”. If you come across any of the following, they all mean the same kind of file.
| What you may see | What it means |
|---|---|
.md / .MD | A Markdown file. Upper or lower case makes no difference |
.markdown | Also a Markdown file, with a longer extension |
| MD file, Markdown file | Names for a .md file |
README.md | A .md often placed as the manual for a program or folder |
It is plain text, so like a .txt file it opens in any text editor. The difference is that in an app that understands Markdown, the marks take the shape of headings and tables.
At a glance, by device
| Device | Just to see what is inside | To read and edit it in shape |
|---|---|---|
| Windows | Notepad | Monoshiri Note (app), VS Code |
| Mac | TextEdit | Monoshiri Note (app), VS Code |
| iPhone, iPad | The Files app | Monoshiri Note (app) |
| Browser only | — | Monoshiri Note (in the browser) |
The editor above is the real Monoshiri Note. Paste the contents of a .md into it to see how it looks, right here.
On Windows
Just to see what is inside: Notepad
- Right-click the
.mdfile - Choose Open with → Notepad
Every word is readable. The marks are shown as they are.
To read it in shape
- Monoshiri Note: install it from the Microsoft Store, then right-click the
.md→ Open with → Markdown Editor - Monoshiri. It opens with headings, tables and checkboxes in shape, and you can edit right there. - VS Code: open the file and press
Ctrl + Shift + Vfor a rendered preview. The editing view and the preview are separate.
On a Mac
Just to see what is inside: TextEdit
- Right-click the
.mdfile - Choose Open With → TextEdit
To read it in shape
- Monoshiri Note: install it from the App Store, then right-click the
.md→ Open With → Monoshiri. That file opens on its own. - VS Code: open the file and press
⌘ + Shift + Vfor the preview.
On iPhone and iPad
A .md you received by email or chat is easier to handle once it is saved in the Files app.
Opening it in Monoshiri Note
- Install Monoshiri Note from the App Store and choose “Inside this app” on the start screen
- In the Files app, move the
.mdinto the ものしりメモ folder under On My iPhone (on an iPad, On My iPad) - Go back to Monoshiri Note and the file is in the list
This storage works without a Google account. Deleting the app deletes the files in it, so keep a copy elsewhere of anything you want to keep.
In a browser, without installing anything
Dropping a .md onto a browser usually just shows the text with its marks.
To read it in shape, either of these is quick:
- Paste it into the editor at the top of this page: open the
.mdin Notepad or similar, copy everything and paste. Nothing is saved, but you can read it without signing in. - Open it in the browser version of Monoshiri Note: for a
.mdthat is in Google Drive. First sign in to the browser version with Google and press View → Add to Drive menu (it asks for one extra permission). After that, right-click the file in Drive → Open with and choose this app; you can edit and save it there.
If the text is garbled
Characters turn into nonsense when the file’s encoding does not match. A .md is normally saved as UTF-8.
- In Notepad on Windows you can pick the encoding again in the File → Open dialog.
- When you save it again yourself, choose UTF-8.
When the .md was made by an AI
A .md made by an AI often contains tables, flowcharts (Mermaid) and maths. In Notepad or TextEdit these stay as marks; in Monoshiri Note a table becomes a ruled table, a flowchart becomes a diagram, and maths is typeset.
After you read and fix it, it is still a .md, so you can hand it back to the AI and ask it to carry on.
Common questions
- What is the .md file extension?
- It is the extension for files written in Markdown. The content is plain text, and marks describe the shape:
#for headings,-for bullets,|for tables. - What is the difference between .md and .markdown?
- None in content: both are Markdown files. The shorter
.mdis far more common. - What is the difference between .md and .txt?
- Both are plain-text files.
.mdsignals “a document whose shape is written with Markdown marks”, and an app that understands Markdown shows it with headings and tables. Rename a.txtto.mdand the text still reads the same. - Which app opens .md files?
- To just see the content, Notepad (Windows) or TextEdit (Mac) will do. To read and edit it with headings and tables in shape, use an editor that understands Markdown. The free Monoshiri Note runs on Windows, Mac, iPhone, iPad and in the browser, and a
.mdtakes shape the moment you open it. - How do I convert a .md file to Word?
- Monoshiri Note does not export to Word. Google Docs can import Markdown, so one way is to bring it in there and download it in Word format (.docx). To paste an AI answer into Word, see the page on marks appearing when you copy.
- Is a .md file safe to open?
- It is plain text; opening it does not run anything. As with any file, take care with where its links lead.
##Related
- When copying brings the marks along Why answers from ChatGPT or Claude turn into a mess of symbols in Word or email, and how to fix it for each place you paste into — plus a way to keep them readable without deleting anything.
- Markdown editors compared 12 Markdown editors that open and edit .md files, compared on price, devices, editing style, where files are stored, and support for tables, diagrams and math: Typora, Obsidian, VS Code, Notion, MarkText, Joplin, Zettlr, iA Writer, Bear, Monoshiri Note and more. With picks by use case, Obsidian vs Typora, and how to move from Notion to .md.
Write one line and see.
Nothing to install — try it straight from the browser. Sign in with Google and the notes are created in your own Drive.
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