text-rendering

  • Revision slug: CSS/text-rendering
  • Revision title: text-rendering
  • Revision id: 25009
  • Created:
  • Creator: Sheppy
  • Is current revision? No
  • Comment update per bug 595688; 71 words added, 36 words removed

Revision Content

{{ CSSRef() }} {{ gecko_minversion_header("1.9") }}

Summary

The text-rendering property is used on Windows and Linux to provide information to the rendering engine about what sorts of tradeoffs to make when rendering text, in order to optimize speed or legibility.

Note: This property has no effect on Mac OS X.

One very visible effect is: optimizeLegibility enables ligatures (ff, fi, fl etc.) in text smaller than 20px for some fonts (e.g. Microsoft's Calibri, Candara, Constantia and Corbel or the DejaVu font family).

  • {{ Xref_cssinitial() }}: auto
  • Applies to: all elements
  • {{ Xref_cssinherited() }}: yes
  • Media: {{ Xref_cssvisual() }}
  • {{ Xref_csscomputed() }}: ?

Syntax

text-rendering:  auto | optimizeSpeed | optimizeLegibility | geometricPrecision | inherit

Values

auto
The browser will make educated guesses about when to optimize for speed, legibility, and geometric precision while drawing text.
In practice, Gecko desktop browsers like Firefox use optimizeLegibility if font size is 20px or larger. Otherwise optimizeSpeed for smaller text.
optimizeSpeed
Gecko will emphasize rendering speed over legibility and geometric precision while drawing text. Disables kerning and ligatures.
optimizeLegibility
Gecko will emphasize legibility over rendering speed and geometric precision. This enables kerning and optional ligatures.
geometricPrecision
Gecko will emphasize geometric precision over rendering speed and legibility; this is currently the same as optimizeLegibility.

Examples

/* make sure all fonts in the HTML document display in all its glory,
   but avoid inadequate ligatures in class foo elements */

body  { text-rendering: optimizeLegibility; }
.foo  { text-rendering: optimizeSpeed; }

Live Example

CSS code Kerning Ligatures
font: 19.9px 'DejaVu Serif',Constantia; LYoWAT ff fi fl ffl
font: 20px 'DejaVu Serif',Constantia; LYoWAT ff fi fl ffl
font: 3em 'DejaVu Serif',Constantia;
text-rendering: optimizeSpeed;
LYoWAT ff fi fl ffl
font: 3em 'Dejavu Serif',Constantia;
text-rendering: optimizeLegibility;
LYoWAT ff fi fl ffl

Notes

The 20px threshold value of the auto keyword can be changed by changing the browser.display.auto_quality_min_font_size preference.

{{ gecko_callout_heading("2.0") }}

The optimizeSpeed option has no effect on Gecko 2.0 {{ geckoRelease("2.0") }}, because the standard code for text rendering is already very fast and there is not a faster code path at this time. See {{ bug("595688") }} for details.

Browser compatibility

Browser Lowest version
Internet Explorer ---
Firefox (Gecko), Windows and Linux 3.0 (1.9)
Firefox (Gecko), Mac OS ---
Opera ---
Safari | Chrome | WebKit 5.0 | 4.0 | 532.5

Specifications

This is an SVG property, it is not defined in any CSS standard. Gecko (Firefox) and WebKit apply text-rendering also to HTML and XML content.

See also

{{ CSS_Reference:Text() }}

Revision Source

<p>{{ CSSRef() }} {{ gecko_minversion_header("1.9") }}</p>
<h3>Summary</h3>
<p>The<code> text-rendering </code>property is used on Windows and Linux to provide information to the rendering engine about what sorts of tradeoffs to make when rendering text, in order to optimize speed or legibility.</p>
<div class="note"><strong>Note:</strong> This property has no effect on Mac OS X.</div>
<p>One very visible effect is:<code> optimizeLegibility </code>enables ligatures (ff, fi, fl etc.) in text smaller than 20px for some fonts (e.g. Microsoft's<em> Calibri, Candara, Constantia and Corbel</em> or the <em>DejaVu</em> font family).</p>
<ul> <li>{{ Xref_cssinitial() }}: auto</li> <li>Applies to: all elements</li> <li>{{ Xref_cssinherited() }}: yes</li> <li>Media: {{ Xref_cssvisual() }}</li> <li>{{ Xref_csscomputed() }}: ?</li>
</ul>
<h3>Syntax</h3>
<pre class="eval">text-rendering:  auto | optimizeSpeed | optimizeLegibility | geometricPrecision | inherit</pre>
<h3>Values</h3>
<dl> <dt><code>auto</code></dt> <dd>The browser will make educated guesses about when to optimize for speed, legibility, and geometric precision while drawing text.</dd> <dd>In practice, Gecko desktop browsers like Firefox use<code> optimizeLegibility </code>if font size is <strong>20px </strong>or larger. Otherwise<code> optimizeSpeed </code>for smaller text.</dd> <dt><code>optimizeSpeed</code></dt> <dd>Gecko will emphasize rendering speed over legibility and geometric precision while drawing text. Disables kerning and ligatures.</dd> <dt><code>optimizeLegibility</code></dt> <dd>Gecko will emphasize legibility over rendering speed and geometric precision. This enables <strong>kerning</strong> and optional <strong>ligatures</strong>.</dd> <dt><code>geometricPrecision</code></dt> <dd>Gecko will emphasize geometric precision over rendering speed and legibility; this is currently the same as<code> optimizeLegibility</code>.</dd>
</dl>
<h3>Examples</h3>
<pre>/* make sure all fonts in the HTML document display in all its glory,
   but avoid inadequate ligatures in class foo elements */

body  { text-rendering: optimizeLegibility; }
.foo  { text-rendering: optimizeSpeed; }</pre>
<h4>Live Example</h4>
<table class="standard-table"> <tbody> <tr> <th>CSS code</th> <th>Kerning</th> <th>Ligatures</th> </tr> <tr style="font: 19.9px 'DejaVu Serif',Constantia"> <td style="font:medium monospace">font: 19.9px 'DejaVu Serif',Constantia;</td> <td>LYoWAT</td> <td>ff fi fl ffl</td> </tr> <tr style="font: 20px 'DejaVu Serif',Constantia"> <td style="font:medium monospace">font: 20px 'DejaVu Serif',Constantia;</td> <td>LYoWAT</td> <td>ff fi fl ffl</td> </tr> <tr style="font: 3em 'DejaVu Serif',Constantia; text-rendering:optimizeSpeed;"> <td style="font:medium monospace">font: 3em 'DejaVu Serif',Constantia;<br> text-rendering: optimizeSpeed;</td> <td>LYoWAT</td> <td>ff fi fl ffl</td> </tr> <tr style="font: 3em 'Dejavu Serif',Constantia; text-rendering:optimizeLegibility;"> <td style="font:medium monospace">font: 3em 'Dejavu Serif',Constantia;<br> text-rendering: optimizeLegibility;</td> <td>LYoWAT</td> <td>ff fi fl ffl</td> </tr> </tbody>
</table>
<h3>Notes</h3>
<p>The 20px threshold value of the<code> auto </code>keyword can be changed by changing the <code>browser.display.auto_quality_min_font_size</code> preference.</p>
<div class="geckoVersionNote">
<p>{{ gecko_callout_heading("2.0") }}</p>
<p>The <code>optimizeSpeed</code> option has no effect on Gecko 2.0 {{ geckoRelease("2.0") }}, because the standard code for text rendering is already very fast and there is not a faster code path at this time. See {{ bug("595688") }} for details.</p>
</div>
<h3>Browser compatibility</h3>
<table class="standard-table"> <tbody> <tr> <th>Browser</th> <th>Lowest version</th> </tr> <tr> <td>Internet Explorer</td> <td>---</td> </tr> <tr> <td>Firefox (Gecko), Windows and Linux</td> <td><strong>3.0</strong> (1.9)</td> </tr> <tr> <td>Firefox (Gecko), Mac OS</td> <td>---</td> </tr> <tr> <td>Opera</td> <td>---</td> </tr> <tr> <td>Safari | Chrome | WebKit</td> <td>5.0 | 4.0 | 532.5</td> </tr> </tbody>
</table>
<h3>Specifications</h3>
<p>This is an SVG property, it is not defined in any CSS standard. Gecko (Firefox) and WebKit apply<code> text-rendering </code>also to HTML and XML content.</p>
<ul> <li><a class="external" href="http://www.w3.org/TR/SVG11/painting.html#TextRenderingProperty" title="http://www.w3.org/TR/SVG11/painting.html#TextRenderingProperty">SVG 1.1 Painting #text-rendering</a></li>
</ul>
<h3>See also</h3>
<p>{{ CSS_Reference:Text() }}</p>
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