You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <compare fromrevid="1" torevid="2" xml:space="preserve">&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Linha 3:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Linha 3:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;div&gt;Consulte o [http://meta.wikimedia.org/wiki/Help:Contents Manual de Usuário] para informações de como usar o software wiki.&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;div&gt;Consulte o [http://meta.wikimedia.org/wiki/Help:Contents Manual de Usuário] para informações de como usar o software wiki.&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td class='diff-deletedline'&gt;&lt;div&gt;== &lt;del class=&quot;diffchange diffchange-inline&quot;&gt;Começando &lt;/del&gt;==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td class='diff-addedline'&gt;&lt;div&gt;&amp;#160;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td class='diff-addedline'&gt;&lt;div&gt;== &lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;Bem vindo ao WikiBase &lt;/ins&gt;==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td class='diff-addedline'&gt;&lt;div&gt;&amp;#160;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;div&gt;* [http://www.mediawiki.org/wiki/Manual:Configuration_settings Lista de opções de configuração]&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;div&gt;* [http://www.mediawiki.org/wiki/Manual:Configuration_settings Lista de opções de configuração]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;div&gt;* [http://www.mediawiki.org/wiki/Manual:FAQ FAQ do MediaWiki]&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;div&gt;* [http://www.mediawiki.org/wiki/Manual:FAQ FAQ do MediaWiki]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;div&gt;* [https://lists.wikimedia.org/mailman/listinfo/mediawiki-announce Lista de discussão com avisos de novas versões do MediaWiki]&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;&amp;#160;&lt;/td&gt;&lt;td class='diff-context'&gt;&lt;div&gt;* [https://lists.wikimedia.org/mailman/listinfo/mediawiki-announce Lista de discussão com avisos de novas versões do MediaWiki]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
</compare>
</api>