Read and write gRPC data using the Postman JSON interface

When sending or receiving a gRPC request or response, the messages being sent back and forth are transmitted in a format called protobuf (protocol buffers). Unlike other data formats such as JSON or XML, which are text-based, protobuf uses a binary format. Binary formats aren't meant to be read by humans, so Postman provides a JSON interface that enables you to read and write data when using gRPC.

JSON interface

Protobuf type	JSON type	JSON example	Notes
message	object	{ "field": 123 }	null is an accepted value for all field types and treated as the default value of the corresponding field type.
enum	string or number	"an_enum"	Both enum names and integer values are accepted.
repeated V	array	[v, ...]
map<K, V>	object	{ "k": v }	All keys are converted to strings.
bool	boolean	true, false
string	string	"Hello World!"
bytes	base64 string or array of bytes (numbers [0, 255])	"SGVsbG8gZ1JQQw=="
int32, sint32, uint32, fixed32, sfixed32	number	1, -10, 0
int64, sint64, uint64, fixed64, sfixed64	number or string	"-1152921504606847254"	Decimal strings are used to increase compatibility with languages that lack a 64-bit integer.
float, double	number or "NaN" or "Infinity" or "-Infinity"	1.1, -10.0, 0, "NaN"

Inspecting fields and types

When composing a message for a gRPC request, you input the data as JSON. Internally, that JSON represents protobuf (protocol buffers) data. For example, you can enter a base64 JSON string to represent bytes in protobuf data.

Postman uses the service definition you select to provide rich type information as you compose your message. When you hover your mouse over various JSON fields or values, a tooltip will explain the underlying protobuf type for that JSON field or value. This can help you remember how to enter certain types of data, or to understand what's going on internally.