How does protocol buffer handle versioning?

How does protocol buffers handle type versioning?

For example, when I need to change a type definition over time? Like adding and removing fields.

Google designed protobuf to be pretty forgiving with versioning:

• unexpected data is either stored as "extensions" (making it round-trip safe), or silently dropped, depending on the implementation
• new fields are generally added as "optional", meaning that old data can be loaded successfully

however:

• do not renumber fields - that would break existing data
• you should not normally change the way any given field is stored (i.e. from a fixed-width 32-bit int to a "varint")

Generally speaking, though - it will just work, and you don't need to worry much about versioning.