I couldn't find any tools to check this, so I built one myself.
This is a little site I built: the Defederation Investigator defed.xyz. With it, you can get a comprehensive view of which instances have blocked yours, as well as which ones you are federated with.
The tool is open source and available on GitHub. Hopefully someone will find it useful, enjoy.
I couldn't find any tools to check this, so I built one myself.
Literally the first link on join-lemmy.org has a table showing all instances and it shows both how many instances that instance is blocking "and* how many other instances are blocking that instance