Trello use “Markdown”, it’s a simple language used to format text.
Here’s what you should know…
The syntax for card descriptions, comments, checklist items, and your bio:
Bold text – Mark text in double asterisks, like **this**, to make it bold.
Italic text – Mark text in single asterisks, like *this*, to make it italic. You can also use underscores to achieve the same, for example, _this_
Strikethrough text – Cross out text by wrapping it in two tildes on each side, like ~~this~~.
Inline code – Include inline formatted code by wrapping it in a single backtick (`) at the beginning and end of the code.
Links – Create a link by putting the link text in brackets and the URL in parentheses, like this.
The syntax for card descriptions and comments only:
Horizontal line – A-line with at least three hyphens will create a horizontal line across the entire description or comment. In card descriptions, include an extra line break after any text before the line of hyphens to prevent the hyphens from being interpreted as header syntax.
Code block – Include formatted code by wrapping it in three backticks (“`) at the beginning and end of the block, or by starting a line with four spaces. Note that the triple backticks have to be on a separate line and ensure you have a blank line before and after the code block.
Indent text / Block Quotes – Indent text by including a “>” in front of each line of the text that you’d like to indent or quote.
Bullet and numbered lists: Preface a series of lines with hyphens or numbers to create a list. Lists will only be formatted if you start a new paragraph (by leaving a blank line before the list).
Any line that begins with a numbered format, even if the number isn’t 1, will automatically create an ordered list. This is as expected and per markdown specs. You can preserve your formatting by putting a ‘\’ before the period, e.g.
The syntax that only works in card descriptions:
Headers – Headers can be marked in several ways. Text in #Single Hashes# will be interpreted like an
<h1> HTML tag (a big header). Text in ##Double Hashes## will be interpreted like an
<h2> HTML tag (a smaller header). In headers, a line of hyphens below text will also be interpreted as an
<h2> tag. Headers can’t be included in the comments.