HTML - Unicode space characters

The space character pixel width below (highlighted in green) assumes a 12 point / 16 pixel font size.

Zero width space

No width, but permits line breaks.
0 em / 0 px

abc

Thecatsatonthemat.

Hair space

The thinnest space available.
1/24 em / 0.7 px

a b c

The cat sat on the mat.

Six per Em space

1/6 em / 2.7 px

a b c

The cat sat on the mat.

Thin space

1/5 em / 3.2 px

a b c

The cat sat on the mat.

Medium Math space

Used around mathematical operators.
4/18 em / 3.6 px

a b c

The cat sat on the mat.

Space

The ASCII space character.
1/4 em / 4 px (approx.)

a b c

The cat sat on the mat.

Punctuation space

Equal to the width of the period.
1/4 em / 4 px (approx.)

a b c

The cat sat on the mat.

Four per Em space

Also called: Mid space
1/4 em / 4 px

a b c

The cat sat on the mat.

Three per Em space

Also called: Thick space
1/3 em / 5.3 px

a b c

The cat sat on the mat.

En space

&ensp;

Equal to the width of the lower-case letter n.
1/2 em / 8 px

a bnc

The cat sat on the mat.

 
&ensp;

En Quad

Same as En space.
1/2 em / 8 px

a b c

The cat sat on the mat.

Figure space

Equal to the width of the digit 0.
1/2 em / 8 px (approx.)

a b c

The cat sat on the mat.

Em space

&emsp;

Equal to the width of the upper-case letter M.
1 em / 16 px

a bMc

The cat sat on the mat.

 
&emsp;

Em Quad

Same as Em space.
1 em / 16 px

a b c

The cat sat on the mat.

Ideograhic space

Equal to the width of a CJK character.
1 em / 16 px

a　b　c

The　cat　sat　on　the　mat.