Regular Expressions 101

1st Alternative

<!--the literal text <!--

Group 1(.*?)

.*?any character, repeated any number of times

-->the literal text -->

2nd Alternative<(?P<tag>[a-z0-9]+?)[^>]*>.*?<\/(?P=tag)>

<the literal < (60₁₀ / 74₈ / 3C₁₆)

Group tag(?P<tag>[a-z0-9]+?)

Character Class[a-z0-9]+?

+?matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case insensitive)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Negated Character Class[^>]*

*matches any number of characters outside the set below:

>the literal > (62₁₀ / 76₈ / 3E₁₆)

.*?any character, repeated any number of times

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

(?P=tag)the text saved by group tag

>the literal > (62₁₀ / 76₈ / 3E₁₆)

3rd Alternative<([a-z0-9]+).*?\/>

<the literal < (60₁₀ / 74₈ / 3C₁₆)

Group 3([a-z0-9]+)

Character Class[a-z0-9]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case insensitive)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

.*?any character, repeated any number of times

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

>the literal > (62₁₀ / 76₈ / 3E₁₆)

4th Alternative[\S ]+

Character Class[\S ]+

+matches at least one character from the set below:

\Sany non-whitespace character

the literal (32₁₀ / 40₈ / 20₁₆)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

s modifier: single line. Allows a dot to match line terminators

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

<!--(.*?)-->|<(?P<tag>[a-z0-9]+?)[^>]*>.*?<\/(?P=tag)>|<([a-z0-9]+).*?\/>|[\S ]+

Test String
New

<!--comment1
 -->
<h1>header</h1>

<img src="http://example.com/img.png" title="single tag"/>

<p>long text</p>

<img src="http://example.com/img2.png"
 title="single tag"/>

&nbsp;

&nbsp;
<!-- comment1 -->
<ul>
    <li>item1</li>
    <li>item2</li>
    <li>item3</li>
</ul>

&nbsp;
some text
&nbsp;


<br class="unclosed">

Regular Expression

Test StringNew

SubstitutionProcessing...

Test String
New

Substitution
Processing...