# What are "blanks"?

**URL:** <https://talk.commonmark.org/t/what-are-blanks/2478>\
**Category:** Spec\
**Tags:** release-1.0\
**Created:** [June 9, 2017, 4:40pm UTC](https://talk.commonmark.org/t/what-are-blanks/2478 "2017-06-09T16:40:35Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Arandur](https://cdn.commonmark.org/letter_avatar_proxy/v2/letter/a/bc79bd/32.png) [@Arandur](https://talk.commonmark.org/u/Arandur)\
**Post date:** [June 9, 2017, 4:40pm UTC](https://talk.commonmark.org/t/what-are-blanks/2478/1 "2017-06-09T16:40:35Z")

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Section 4.2 ATX Headings states:

> Leading and trailing blanks are ignored in parsing inline content

and then gives `# foo ` =\> `<h1>foo</h1>` as an example.

The term “blank” appears in the spec (v0.27) 85 times; 83 times in the phrase “blank line[s]”, once in the phrase “blank HTML comment”, and once in the above-quoted statement.

Earlier, in section 2.1, the spec takes care to define the terms “blank _line_”, “whitespace character”, “whitespace”, “Unicode whitespace character”, “Unicode whitespace”, “space”, and “non-whitespace character”. But the term “blank”, in reference to a character, is nowhere defined, which renders the above-quoted statement ambiguous.

I think that it’s clear from context and from precedent that “blank” should here be treated as synonymous with “space”, but I believe it would be prudent to make that explicit in the text.

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**Author:** ![Arandur](https://cdn.commonmark.org/letter_avatar_proxy/v2/letter/a/bc79bd/32.png) [@Arandur](https://talk.commonmark.org/u/Arandur)\
**Post date:** [June 9, 2017, 6:58pm UTC](https://talk.commonmark.org/t/what-are-blanks/2478/2 "2017-06-09T18:58:23Z")

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> [@Arandur](#):
>
> I think that it’s clear from context and from precedent that “blank” should here be treated as synonymous with “space”, but I believe it would be prudent to make that explicit in the text.

The Javascript reference implementation at [try.commonmark.org](http://try.commonmark.org) appears to take a different approach than I expected, and treats U+0009 (horizontal tab) as a “blank.” This is evidence in favor of the proposition that “blank” should be synonymous with “whitespace character”, although it could still be “Unicode whitespace character”.

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**Author:** ![jgm](https://cdn.commonmark.org/user_avatar/talk.commonmark.org/jgm/32/1360_2.png) [@jgm](https://talk.commonmark.org/u/jgm)\
**Post date:** [June 11, 2017, 9:05am UTC](https://talk.commonmark.org/t/what-are-blanks/2478/3 "2017-06-11T09:05:12Z")

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It would be best to avoid the term “blanks” and rewrite  
using one of the defined terms you mentioned in each case.

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**Author:** ![handcraftedbits](https://cdn.commonmark.org/letter_avatar_proxy/v2/letter/h/b5e925/32.png) [@handcraftedbits](https://talk.commonmark.org/u/handcraftedbits)\
**Post date:** [June 19, 2017, 1:25pm UTC](https://talk.commonmark.org/t/what-are-blanks/2478/4 "2017-06-19T13:25:38Z")

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From what I’ve seen in the reference implementations, “blank” is a space or tab, NOT all whitespace (like \f or \v).

Furthermore, even when the a definition links the term “whitespace” in many cases I’ve noticed that the reference implementations really mean space or tab.