Preview Markdown in Textmode on Mac
While you edit a Markdown document, you can show how it reads when rendered, in a preview beside the editor.
Show or hide the preview
In the Textmode app 
on your Mac, open a document whose syntax is Markdown.
Choose View > Show Markdown Preview.
The window splits in two, with the editor on the left and the preview on the right.
To hide the preview, choose View > Hide Markdown Preview.
The preview updates a moment after you stop typing. You can select and copy text in the preview, but you can’t edit it.
Note: Show Markdown Preview is dimmed when the syntax of the document isn’t Markdown. If you change the syntax to another one while the preview is shown, the preview closes.
What the preview shows
Headings, paragraphs, and bold, italic, strikethrough, and inline code text.
Numbered and bulleted lists, including lists inside lists.
Tables as a grid, with a bold header row and the column alignment set in the Markdown.
Block quotes with a bar along the left side.
Fenced code blocks in a monospaced font on a shaded background.
Links open when you click them only if they are http, https, or mailto links, and other links are shown as text.
Images are not loaded: in place of an image, the preview shows its alternative text, as in “[Image: a diagram]”.
Preview a large document
When the document holds more than 2 MB of text, the preview stops updating as you type and shows the note “Preview pauses above 2 MB; choose Refresh Preview to update.” at the top.
To render the current text, choose View > Refresh Preview.
What to keep in mind
The preview belongs to its window. Each window shows or hides its own preview.
Textmode doesn’t remember that the preview was shown. After you quit and open the app again, show the preview again.