Protobuf Formatter Online - Format & Validate .proto Files Free

Example .proto file:

syntax = "proto3";

package example;

message User {
  int32 id = 1;
  string name = 2;
  string email = 3;
  repeated string roles = 4;
}

service UserService {
  rpc GetUser(UserRequest) returns (User);
  rpc ListUsers(Empty) returns (UserList);
}

How to Use the Protobuf Formatter

Step 1: Paste Proto File

Copy your .proto file content and paste it into the input area. The formatter handles proto2 and proto3 syntax, including messages, services, enums, and nested definitions.

Step 2: Format or Validate

Click "Format Proto" to beautify your file with proper indentation and spacing. Use "Validate" to check for syntax errors before formatting. The formatter preserves comments and organizes definitions logically.

Step 3: Use Formatted Output

Copy the formatted proto to your clipboard or download it as a .proto file. Use the formatted version in your project for better readability and team collaboration.

Best Practices

Keep messages focused and single-purpose. Use meaningful field names. Number fields sequentially starting from 1. Reserve field numbers for deleted fields to maintain backward compatibility.

Common Use Cases

1. gRPC Service Development

Format .proto files that define gRPC services. Well-formatted proto files make it easier to understand service contracts and generate client/server code in multiple languages.

2. Microservices Communication

Use Protobuf for efficient inter-service communication. Format proto files to define message contracts between microservices, ensuring type safety and backward compatibility.

3. Data Storage

Store structured data in Protobuf format for efficient serialization. Format proto schemas to document data structures and generate code for reading/writing data.

4. API Documentation

Well-formatted proto files serve as API documentation. They clearly show message structures, field types, and service methods, making it easy for developers to understand the API.

5. Code Generation

Format proto files before running the protobuf compiler. Clean, well-formatted proto files generate cleaner code and are easier to maintain as your API evolves.

Protobuf Examples

Example 1: Simple Message

syntax = "proto3";

message Person {
  string name = 1;
  int32 age = 2;
  string email = 3;
}

Example 2: Nested Messages

syntax = "proto3";

message Address {
  string street = 1;
  string city = 2;
  string country = 3;
}

message Person {
  string name = 1;
  Address address = 2;
}

Example 3: Enum Definition

syntax = "proto3";

enum Status {
  UNKNOWN = 0;
  ACTIVE = 1;
  INACTIVE = 2;
  DELETED = 3;
}

message User {
  string name = 1;
  Status status = 2;
}

Example 4: gRPC Service

syntax = "proto3";

service UserService {
  rpc CreateUser(CreateUserRequest) returns (User);
  rpc GetUser(GetUserRequest) returns (User);
  rpc UpdateUser(UpdateUserRequest) returns (User);
  rpc DeleteUser(DeleteUserRequest) returns (Empty);
  rpc ListUsers(ListUsersRequest) returns (UserList);
}

Example 5: Repeated and Map Fields

syntax = "proto3";

message User {
  string name = 1;
  repeated string emails = 2;
  map<string, string> metadata = 3;
  repeated Address addresses = 4;
}

Frequently Asked Questions