Sergei Zobov | Blog Software and robotics engineer

Human-readable protobuf -- text and JSON formats.


This article can be interesting for you if you use or plan to use protobuf. Protobuf is a binary format and it’s wonderful, but sometimes we need something more readable, and protobuf can give it to us with text or JSON formats.


For example we have a messages definition message.proto, like this:

message Bar {
    string name = 1;
message Foo {
    string super_name = 1;
    Bar bar = 2;

Now we can create a messages from this definition:

#include <google/protobuf/text_format.h>
#include <google/protobuf/util/json_util.h>
#include <our_proto_files/proto.h>

// Create and fill messages
our_proto::Foo fooInstance;
fooInstance.set_super_name("some cool super name");

auto barInstance = fooInstance.mutable_bar();
barInstance.set_name("another, but also cool name");

// Make prototext version of our messages
std::string prototextOutput;
google::protobuf::TextFormat::PrintToString(fooInstance, &prototextOutput);

// Make also JSON version
std::string JSONOutput;
google::protobuf::util::MessageToJsonString(fooInstance, &JSONOutput);

// Write strings with serialized messages into the files

Now you can see, that so prototext output looks like this:

super_name: "some cool super name"
bar {
  name: "another, but also cool name"

And JSON like this:

{"super_name":"some cool super name","bar":{"name":"another, but also cool name"}}

Unfortunately, JSON is not so pretty by default, but it stays quite readable, than protobuf.

This protobuf’s option can be useful in some cases. For example, you need to transfer files and you want to add some readable metadata with it. You don’t need to add additional dependency or write serialization code, you can just use this option out of the box.