Has anyone defederated your instance? Introducing Defederation Investigator
Has anyone defederated your instance? Introducing Defederation Investigator
defed.xyz
Defederation Investigator

EDIT 3: All good now, the DNS has done its thing and defed.xyz is fully operational! Once again, thank you all for having checked out my tool, it means a lot to me.
ORIGINAL POST: 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.