What are some reasonable approaches in client-side JS to detect whether a given URL is blocked for the user on whose browser the code is running? Is there a lib or other project that does this for some types of blocks?
In Russia, for example, https://linkedin.com redirects to http://denypage.ru/ due to being on the government's blacklist. But other governments:
- simply throttle, which is harder to detect
- block the URLs used by messenger apps
- force platforms to block specific accounts
...
See also: Tor's OONI project, Twitter's policy on so-called Country Withheld Content™, TurkeyBlocks.org's methodology