regex101: PCRE (Legacy) Match Workspace

Positive Lookbehind(?<=<img)

<imgthe literal text <img (case sensitive)

Group 1([^>]*)

Negated Character Class[^>]*

*matches any number of characters outside the set below:

>the literal > (62₁₀ / 76₈ / 3E₁₆)

Group 2([0-9]+.imgdomain\.com)

Character Class[0-9]+

+matches at least one character from the set below:

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

.any character (except for line terminators)

imgdomainthe literal text imgdomain (case sensitive)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

comthe literal text com (case sensitive)

Negated Character Class[^>]*?

*?matches any number of characters outside the set below:

>the literal > (62₁₀ / 76₈ / 3E₁₆)

Global pattern flags

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

Search reference

Regular Expression

(?<=<img)([^>]*)([0-9]+.imgdomain\.com)[^>]*?>

New

<div class="separator" style="clear: both; text-align: center;">
<img src="/demodomain.com/-13ucJuEQEUw/linktoimg.png"><a href="https://12.imgdomain.com/-13ucJuEQEUw/linktoimg.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="618" data-original-width="1062" height="372" src="https://21.imgdomain.com/-13ucJuEQEUw/WsGsjY2E2bI/-13ucJuEQEUw/linktoimg.jpg" width="640"></a></div>

<div class="separator" style="clear: both; text-align: center;"><img src="/demodomain.com/-13ucJuEQEUw/linktoimg.png"><a href="https://12.imgdomain.com/-13ucJuEQEUw/linktoimg.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="618" data-original-width="1062" height="372" src="https://21.imgdomain.com/-13ucJuEQEUw/WsGsjY2E2bI/-13ucJuEQEUw/linktoimg.jpg" width="640"></a></div>

Regular Expressions 101

Regular Expression

Extraction