<div>
What's the context? You probably don't need a regex. You can do the lot with a few replaces. A lot easier to read for those that don't do regex's. Probably not as efficient as a rgex but it works, and unless you're doing millions of calls to this in one go, the efficiency will porbably not affect you.<br />
<br />
<br />

<pre><code class="code-1 nolinks" id="code-20-41397314-1"><span>function fixFileName(psFileName)</span>
<span>{</span>
<span>  return psFileName.replace('https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/', '').replace('_M', '').replace('_thumb', '').replace('?response-content-disposition', '');</span>
<span>}</span>
</code></pre>
</div>


<div>
I need a regex, the system I use requires a regex input to do its processing.
</div>


<div>
For me this works:<br />

<pre><code class="code-1 nolinks" id="code-20-41397338-1"><span>/.*\/(.*?)_?[SMLt]?[humb]*\.jpg.*/</span>
</code></pre>
<br />
You can test and tweak and understand it @ <a href="https://regex101.com/" rel="ugc">https://regex101.com/</a>
</div>


<div>
return psFileName.replaceFirst(&quot;.<wbr />*/(.*?)(_(<wbr />S|M|L|thum<wbr />b))?\\.jpg<wbr />.*&quot;, &quot;$1&quot;);
</div>


<div>
Doesn't work for me, please see it live at <a href="http://www.regexr.com/3ch31" rel="ugc">http://www.regexr.com/3ch31</a>
</div>


<div>
ozo doesn't work either <a href="http://www.regexr.com/3ch34" rel="ugc">http://www.regexr.com/3ch34</a>
</div>


<div>
try:<br />

<pre><code class="code-1 nolinks" id="code-20-41397366-1"><span>^.*\/(.*(\_(S|M|L|thumb))?\.jpg).*$</span>
</code></pre>
please note that the regexr site shows only first match from the whole string, so if you paste all of the URLs in the regexr only the first will match, you can delete one by one and see if the next one matches - as you would also process each line by line
</div>


<div>
If you add the flag global you have 9 matches
</div>


<div>
<pre><code class="code-1 nolinks" id="code-20-41397373-1"><span>/https://.*/(.*)_/m</span>
</code></pre>
HTH,<br />
Dan
</div>


<div>
with my regex if you go with global and multiline flags all lines match<br />
<a href="http://www.regexr.com/3ch37" rel="ugc">http://www.regexr.com/3ch3<wbr />7</a>
</div>


<div>
This makes me think my solution works: <a href="https://regex101.com/r/zL8dS5/1" rel="ugc">https://regex101.com/r/zL8dS5/1</a>
</div>


<div>
Errata:<br />

<pre><code class="code-1 nolinks" id="code-20-41397383-1"><span>/https://.*/(.*)_(M|L|thumb)*.*\./g</span>
</code></pre>
</div>


<div>
<a href="http://regexr.com/3ch3d" rel="ugc">http://regexr.com/3ch3d</a>
</div>


<div>
Hi,<br />
<br />
pls try<br />
<br />

<pre><code class="code-1 nolinks" id="code-20-41397388-1"><span>.*\/(.*?)(_([SML]|thumb))?\.jpg.*</span>
</code></pre>
Regards
</div>


<div>
<div class="content wysiwyg-content">
What regex would capture the file name not including <b>_[S|M|L|thumb].jpg</b> in all the following examples:<br />
<br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/AS6_1683-77_S.jpg" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/AS6_1683-77_S.jpg</a><br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/preview/AS6_1683-77_M.jpg" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/preview/AS6_1683-77_M.jpg</a><br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/content/AS6_1683-77.jpg?response-content-disposition" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/content/AS6_1683-77.jpg?response-content-disposition</a><br />
<b>AS6_1683-77</b><br />
<br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/AS6_3900-136_thumb.jpg" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/AS6_3900-136_thumb.jpg</a><br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/preview/AS6_3900-136_M.jpg" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/preview/AS6_3900-136_M.jpg</a><br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/content/AS6_3900-136.jpg?response-content-disposition" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/content/AS6_3900-136.jpg?response-content-disposition</a><br />
<b>AS6_3900-136</b><br />
<br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_S.jpg" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_S.jpg</a><br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/preview/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_M.jpg" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/preview/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_M.jpg</a><br />
<a href="https://d1yl1kh78jj1rr.cloudfront.net/content/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_L.jpg?response-content-disposition" rel="ugc">https://d1yl1kh78jj1rr.cloudfront.net/content/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_L.jpg?response-content-disposition</a><br />
<b>hand-drawn-illustration-of<wbr />-cocktail-<wbr />vector-col<wbr />lection_X1<wbr />EVoU</b><br />
<br />
Note: it should be the same regex for all of them.
</div>
</div>


What regex would capture the file name not including _[S|M|L|thumb].jpg in all the following examples:

https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/AS6_1683-77_S.jpg
https://d1yl1kh78jj1rr.cloudfront.net/preview/AS6_1683-77_M.jpg
https://d1yl1kh78jj1rr.cloudfront.net/content/AS6_1683-77.jpg?response-content-disposition
AS6_1683-77

https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/AS6_3900-136_thumb.jpg
https://d1yl1kh78jj1rr.cloudfront.net/preview/AS6_3900-136_M.jpg
https://d1yl1kh78jj1rr.cloudfront.net/content/AS6_3900-136.jpg?response-content-disposition
AS6_3900-136

https://d1yl1kh78jj1rr.cloudfront.net/thumbnail/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_S.jpg
https://d1yl1kh78jj1rr.cloudfront.net/preview/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_M.jpg
https://d1yl1kh78jj1rr.cloudfront.net/content/hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU_L.jpg?response-content-disposition
hand-drawn-illustration-of-cocktail-vector-collection_X1EVoU

Note: it should be the same regex for all of them.

regex needed

A regular expression ("regex") is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. "find and replace"-like operations. Regular expression processors are found in several search engines, search and replace dialogs of several word processors and text editors, and in the command lines of text processing utilities, such as sed and AWK. Many programming languages provide regular expression capabilities, some built-in, for example Perl, JavaScript, Ruby, AWK, and Tcl, and others via a standard library, for example .NET languages, Java, Python and C++ (since C++11). Most other languages offer regular expressions via a library.

Regular Expressions

JavaScript is a dynamic, object-based language commonly used for client-side scripting in web browsers. Recently, server side JavaScript frameworks have also emerged. JavaScript runs on nearly every operating system and  in almost every mainstream web browser.