Thin space ( ) in HTML
A thin space is a fixed width space narrower than an ordinary one, used for fine typographic adjustment. Its named reference is   and its code point is U+2009.
At a glance
- Character
- (invisible, about one sixth of an em)
- Named entity
-  
- Decimal reference
-  
- Hex reference
-  
- Unicode code point
- U+2009
- Unicode name
- THIN SPACE
- In the entity reference
- Not in the 152 entity list
In detail
The thin space is roughly a sixth of an em, though the exact width is a font decision. Its jobs are all small adjustments: separating a quotation mark from the text it encloses, opening up the space around a mathematical operator, and separating groups of digits in a large number where a comma or a full stop would be ambiguous across locales.
That last use is the standards backed one. The international recommendation for large numbers is to group digits with a thin space rather than with a comma or a point, precisely because different countries read those two characters as opposite things. A number grouped with spaces is unambiguous to every reader.
There is one important limitation: this character is breakable. A line can wrap at it, so a number grouped with thin spaces can split across two lines with a group stranded. The character that avoids this is the narrow no-break space at U+202F, which is the same visual width and does not permit a break, and which is what a careful implementation actually uses inside numbers.
French typography needs the narrow no-break space for the same reason. It goes inside guillemets and before certain punctuation marks, and using a breakable space there produces a quotation that can wrap immediately after its opening mark. Neither character is in the entity reference tool's list, so both are written numerically.
Examples
<p>1 234 567 m</p>  is U+202F, the narrow no-break space. A plain thin space here would allow a wrap between the digit groups.
<p>a ± b</p>
<p>12 × 8 = 96</p>Things that catch people out
- The thin space permits a line break. Inside a number or a French quotation, use the narrow no-break space at U+202F instead.
- Neither of these characters is an ordinary space to a text search, so grouped numbers will not match a query typed with commas.
- Font support for the narrow no-break space is good but not universal, and a font without it may fall back to something visibly wider.
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