Dear all, afte Fuel being available for both Squeak and Pharo, I experimented a little bit. So, I put a new snapshot.fuel beside the snapshot.bin in the mcz zips (same for patch.* in mcd). But to make it easier in the future to experiment with things, I included a small facility to extend serializers/materializers or similar things more easily. How is it done? Example: new serializer in MCZ files: After my patch, include MCMczWriter class>>serializerMine ^ [:writer :snapshot | writer writeSnapshotAsMyFormat: snapshot] and MCMczWriter>>writeSnapshotAsMyFormat: snapshot self addString: (self doSomeConversion: aSnapshot) at: 'snapshot.myformat'. as Extension methods in MCMczWriter, and execute MCMczWriter populateSerializers. Now, a new file member is added to every new mcz file. As an example, I have done such thing for Fuel. Don't worry, it just uses the default behavior if Fuel is not present in either the image or the mcz-file. Best, -Tobias PS: for Squeak, see Inbox Monticello-topa.491, And I also have an MCD attached that should help using the code elsewhere.