mdrefine

structure/unspaced-heading ​

Reports text that would be a # heading with a space after its hashes, such as #Installation or ##Usage##. Every supported renderer needs blank space after the opening hashes, so it shows the line as paragraph text with its #.

Problem rule, reported only. Presets: none. Dialects: all. Options: none.

Reported:

markdown
#Installation

##Usage##

Not reported:

markdown
# Installation

#123 fixed the crash.

Edge cases and advanced usage ​

Details: adding the space turns text into a heading, which changes the outline and may not be what was meant, so the rule only reports. One to six # start the line, followed by a letter or a digit, also after a *, _, or backtick that opens emphasis or code. A line that ends with a run of # gets the advice to add spaces inside the hashes too. Only the first line of a paragraph is checked, after its container's markers, as in > #Note or - #Item, and, outside CommonMark, the line below an alert's or callout's marker, which starts its body. A paragraph's later lines are not checked, because wrapped text can start a line with any word.

Not checked: text that only resembles a heading:

  • a single # before a number, as in an issue reference such as #123 fixed;
  • another character after the hashes, as in a shebang (#!/bin/sh) or #[attribute];
  • seven or more hashes, and an escaped \#;
  • a heading whose closing hashes follow its text without a space, such as # C#, which is a heading whose text ends with #.

Dialect notes ​

In Obsidian: # and a word is a tag, as in #project text, and is not reported.