SSEM User Guide
For SSEM Markdown Editor 1.0.2
1. Install
- On the Chrome Web Store, click Add to Chrome. Chrome installs updates automatically.
- Click the puzzle-piece Extensions icon in the toolbar and pin SSEM Markdown Editor. Clicking the pinned icon opens the settings popup.
2. Opening Markdown files
Open any page whose address ends in .md, .mdx, .mkd or .markdown (upper-case extensions and addresses with a ? query included) and SSEM Markdown Editor renders it automatically. There’s nothing to click.
- Files on the web: works where the server sends the raw Markdown text. On GitHub, for example, it works on the
raw.githubusercontent.comaddress you get with the Raw button — not on the repository page (github.com/…/README.md), which GitHub has already turned into HTML. - Files on your computer: drag the file into a Chrome window or type a
file:///path in the address bar. First allow access to file URLs. - Folders: open a folder on your computer (
file:///…/) and itsREADME.md— or, if there’s none,index.md— opens automatically. Turn this off with Auto index.md in the popup.
3. Files on your computer (Allow access to file URLs)
For security, Chrome doesn’t let extensions read file:// addresses by default. Allow it once to view Markdown files on your computer. Until you do, the popup shows a red notice at the top.
- Type
chrome://extensionsin the address bar, or choose the Extensions icon › Manage extensions. - Click Details under SSEM Markdown Editor.
- Turn on Allow access to file URLs.
- Reload any Markdown tabs that are already open.
Even with this on, the extension only handles files you open in the browser. It never looks for or reads other files on your computer.
4. View modes
Cycle through the three modes with the buttons at the top of the document or Ctrl/⌘ + E. The mode a document opens in is set with View Mode in the popup (Split after installation).
| Mode | What you see |
|---|---|
| Editor | Only the Markdown source, with line numbers, ready to edit. |
| Split | Edit on the left; the preview on the right updates as you type. |
| Viewer | Only the rendered document — the cleanest mode for reading. |
The sidebar button at the top left (or Alt + Shift + B) opens an outline built from the headings. Click an entry to jump to that heading.
5. Editing and saving
You can edit the source in Editor and Split modes. Browsers don’t allow extensions to overwrite files, so edits are not saved to the original file.
- Click the download button at the top of the document or press Ctrl/⌘ + S to start a browser download with the same file name. Depending on your Chrome settings it goes to your Downloads folder or Chrome asks where to save it.
- To update the original, replace it with the downloaded file yourself.
- If you close or reload the tab without downloading, your edits are gone.
If auto-refresh is on, Viewer mode refills the page from the original file whenever it changes. Edit in Editor or Split mode — auto-refresh pauses there.
6. Settings popup
Click the SSEM Markdown Editor icon in the toolbar to open the settings popup. Changes apply to open documents immediately and are saved in this browser.
| Setting | What it does |
|---|---|
| Enable | When off, Markdown pages aren’t rendered and you see the browser’s plain-text view. |
| Centered | Narrows the document and centers it (AltShiftC). |
| Auto Refresh | In Viewer mode, re-reads the same address at short intervals and shows changes to the file (AltShiftR). Handy while writing in another editor. |
| Auto index.md | Opening a folder on your computer opens its README.md or index.md. |
| Plugins | Turns each extended syntax on or off. |
| View Mode | The mode documents open in (Split, Editor, Viewer). |
| Theme | Light, Dark or Auto (follows your operating system). |
| Language | The popup’s language: English, 한국어, 简体中文, 繁體中文 or Українська. |
7. Supported syntax
Besides standard Markdown (CommonMark) with tables and highlighted code blocks, the following extensions can be switched on or off under Plugins in the popup. All are on after installation.
| Plugin | How to write it |
|---|---|
| Emoji | :rocket: → 🚀 |
| Sup · Sub | x^2^, H~2~O |
| Insert · Mark | ++inserted++, ==highlighted== |
| Abbrev | *[HTML]: Hyper Text Markup Language |
| Definition | A term, then : definition on the next line |
| Footnote | Text[^1] … [^1]: The footnote |
| TaskList | - [x] Done, - [ ] To do |
| TOC | Write [[toc]] where the table of contents should go. |
| Alert | > [!NOTE], [!TIP], [!IMPORTANT], [!WARNING], [!CAUTION] |
| Formula · Mermaid | See Diagrams and math |
Use the copy button at the top right of a code block to copy the code, and click an image in the document to enlarge it.
8. Diagrams and math
Mermaid diagrams
Code blocks whose language is mermaid are drawn as diagrams. With Mermaid 10 you get flowcharts, sequence, class, state, Gantt and pie charts, quadrantChart, mindmap, timeline and more.
```mermaid
graph LR
A[Edit] --> B[Preview] --> C[Save]
```If you see an error instead of a diagram, check the Mermaid syntax (brackets and quotes especially). Diagrams are redrawn to match when you change the theme.
KaTeX math
Wrap inline math in $…$ and display math in $$…$$.
Energy: $E = mc^2$
$$
\sum_{i=1}^{n} i = \frac{n(n+1)}{2}
$$9. Keyboard shortcuts
| Shortcut | Action |
|---|---|
| Ctrl/⌘ + S | Download the edited document |
| Ctrl/⌘ + E | Switch view mode (Split → Editor → Viewer) |
| Alt + Shift + B | Show or hide the outline sidebar |
| Alt + Shift + C | Toggle centered layout |
| Alt + Shift + R | Toggle auto-refresh |
| Alt + Shift + T | Switch between light and dark themes |
On a Mac, Alt is the ⌥ Option key. You can change or remove the Alt + Shift shortcuts at chrome://extensions/shortcuts. If another extension uses the same combination, Chrome assigns it to only one of them.
10. Turning off and removing
- Pause: turn off Enable in the settings popup to see Markdown files as plain text.
- Disable: switch SSEM Markdown Editor off at
chrome://extensions. - Remove: right-click the toolbar icon and choose Remove from Chrome, or click Remove at
chrome://extensions. Settings stored in this browser are removed too. After removal, Chrome opens the developer’s web page once in a new tab.
More questions? See Support.