How to get Fragment value from url in Drupal 8? I need to get the Fragment value from url like: admin/config/system/meta_custom?query=test#abc=xyz in Drupal 8.

Need value of abc - ideally using Drupal's API, rather than doing my own Url Parsing.
You could use it like this: 

$path = \Drupal::request()->getpathInfo();
$arg  = explode('/',$path);

It gives:  

Array
(
    [0] => 
    [1] => node
    [2] => add
    [3] => application
)