double | | double | double | float | float64 | double | float | Float |

float | | float | float | float | float32 | float | float | Float |

int32 | Uses variable-length encoding. Inefficient for encoding negative numbers - if your field is likely to have negative values, use sint32 instead. | int32 | int | int | int32 | int | integer | Bignum or Fixnum (as required) |

int64 | Uses variable-length encoding. Inefficient for encoding negative numbers - if your field is likely to have negative values, use sint64 instead. | int64 | long | int/long | int64 | long | integer/string | Bignum |

uint32 | Uses variable-length encoding. | uint32 | int | int/long | uint32 | uint | integer | Bignum or Fixnum (as required) |

uint64 | Uses variable-length encoding. | uint64 | long | int/long | uint64 | ulong | integer/string | Bignum or Fixnum (as required) |

sint32 | Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int32s. | int32 | int | int | int32 | int | integer | Bignum or Fixnum (as required) |

sint64 | Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int64s. | int64 | long | int/long | int64 | long | integer/string | Bignum |

fixed32 | Always four bytes. More efficient than uint32 if values are often greater than 2^28. | uint32 | int | int | uint32 | uint | integer | Bignum or Fixnum (as required) |

fixed64 | Always eight bytes. More efficient than uint64 if values are often greater than 2^56. | uint64 | long | int/long | uint64 | ulong | integer/string | Bignum |

sfixed32 | Always four bytes. | int32 | int | int | int32 | int | integer | Bignum or Fixnum (as required) |

sfixed64 | Always eight bytes. | int64 | long | int/long | int64 | long | integer/string | Bignum |

bool | | bool | boolean | boolean | bool | bool | boolean | TrueClass/FalseClass |

string | A string must always contain UTF-8 encoded or 7-bit ASCII text. | string | String | str/unicode | string | string | string | String (UTF-8) |

bytes | May contain any arbitrary sequence of bytes. | string | ByteString | str | []byte | ByteString | string | String (ASCII-8BIT) |