File extension for serialized protobuf output

Question

Seems odd that I can't find the answer to this, but what file extension are you supposed to use when storing serialized protobuf output in a file? Just .protobuf? The json equivalent of what I am talking about would be a .json file.

Answer 1

I just use .bin, but there's no actual standard here AFAIK. If protoc -o (which emits a .proto schema in protobuf binary format as a FileDescriptorSet) had taken a directory like all the other output options do, we could have used that as a de-facto answer, but protoc -o is unusual in that it takes a file instead. In an old post on the protobuf group, Kenton Varda (one of the original authors) suggests that the file extension should be implementation specific (meaning: you decide) rather than simply referring to the format: https://groups.google.com/forum/#!topic/protobuf/JWZx9n8CUvw