---
slug: /en/sql-reference/data-types/data-types-binary-encoding
sidebar_position: 56
sidebar_label: Data types binary encoding specification.
---


# Data types binary encoding specification

This specification describes the binary format that can be used for binary encoding and decoding of ClickHouse data types. This format is used in `Dynamic` column [binary serialization](dynamic.md#binary-output-format) and can be used in input/output formats [RowBinaryWithNamesAndTypes](../../interfaces/formats.md#rowbinarywithnamesandtypes) and [Native](../../interfaces/formats.md#native) under corresponding settings.

The table below describes how each data type is represented in binary format. Each data type encoding consist of 1 byte that indicates the type and some optional additional information.
`var_uint` in the binary encoding means that the size is encoded using Variable-Length Quantity compression.

| ClickHouse data type                                                                                      | Binary encoding                                                                                                                                                                                                                                                                                                                                                            |
|-----------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `Nothing`                                                                                                 | `0x00`                                                                                                                                                                                                                                                                                                                                                                     |
| `UInt8`                                                                                                   | `0x01`                                                                                                                                                                                                                                                                                                                                                                     |
| `UInt16`                                                                                                  | `0x02`                                                                                                                                                                                                                                                                                                                                                                     |
| `UInt32`                                                                                                  | `0x03`                                                                                                                                                                                                                                                                                                                                                                     |
| `UInt64`                                                                                                  | `0x04`                                                                                                                                                                                                                                                                                                                                                                     |
| `UInt128`                                                                                                 | `0x05`                                                                                                                                                                                                                                                                                                                                                                     |
| `UInt256`                                                                                                 | `0x06`                                                                                                                                                                                                                                                                                                                                                                     |
| `Int8`                                                                                                    | `0x07`                                                                                                                                                                                                                                                                                                                                                                     |
| `Int16`                                                                                                   | `0x08`                                                                                                                                                                                                                                                                                                                                                                     |
| `Int32`                                                                                                   | `0x09`                                                                                                                                                                                                                                                                                                                                                                     |
| `Int64`                                                                                                   | `0x0A`                                                                                                                                                                                                                                                                                                                                                                     |
| `Int128`                                                                                                  | `0x0B`                                                                                                                                                                                                                                                                                                                                                                     |
| `Int256`                                                                                                  | `0x0C`                                                                                                                                                                                                                                                                                                                                                                     |
| `Float32`                                                                                                 | `0x0D`                                                                                                                                                                                                                                                                                                                                                                     |
| `Float64`                                                                                                 | `0x0E`                                                                                                                                                                                                                                                                                                                                                                     |
| `Date`                                                                                                    | `0x0F`                                                                                                                                                                                                                                                                                                                                                                     |
| `Date32`                                                                                                  | `0x10`                                                                                                                                                                                                                                                                                                                                                                     |
| `DateTime`                                                                                                | `0x11`                                                                                                                                                                                                                                                                                                                                                                     |
| `DateTime(time_zone)`                                                                                     | `0x12<var_uint_time_zone_name_size><time_zone_name_data>`                                                                                                                                                                                                                                                                                                                  |
| `DateTime64(P)`                                                                                           | `0x13<uint8_precision>`                                                                                                                                                                                                                                                                                                                                                    |
| `DateTime64(P, time_zone)`                                                                                | `0x14<uint8_precision><var_uint_time_zone_name_size><time_zone_name_data>`                                                                                                                                                                                                                                                                                                 |
| `String`                                                                                                  | `0x15`                                                                                                                                                                                                                                                                                                                                                                     |
| `FixedString(N)`                                                                                          | `0x16<var_uint_size>`                                                                                                                                                                                                                                                                                                                                                      |
| `Enum8`                                                                                                   | `0x17<var_uint_number_of_elements><var_uint_name_size_1><name_data_1><int8_value_1>...<var_uint_name_size_N><name_data_N><int8_value_N>`                                                                                                                                                                                                                                   |
| `Enum16`                                                                                                  | `0x18<var_uint_number_of_elements><var_uint_name_size_1><name_data_1><int16_little_endian_value_1>...><var_uint_name_size_N><name_data_N><int16_little_endian_value_N>`                                                                                                                                                                                                    |
| `Decimal32(P, S)`                                                                                         | `0x19<uint8_precision><uint8_scale>`                                                                                                                                                                                                                                                                                                                                       |
| `Decimal64(P, S)`                                                                                         | `0x1A<uint8_precision><uint8_scale>`                                                                                                                                                                                                                                                                                                                                       |
| `Decimal128(P, S)`                                                                                        | `0x1B<uint8_precision><uint8_scale>`                                                                                                                                                                                                                                                                                                                                       |
| `Decimal256(P, S)`                                                                                        | `0x1C<uint8_precision><uint8_scale>`                                                                                                                                                                                                                                                                                                                                       |
| `UUID`                                                                                                    | `0x1D`                                                                                                                                                                                                                                                                                                                                                                     |
| `Array(T)`                                                                                                | `0x1E<nested_type_encoding>`                                                                                                                                                                                                                                                                                                                                               |
| `Tuple(T1, ..., TN)`                                                                                      | `0x1F<var_uint_number_of_elements><nested_type_encoding_1>...<nested_type_encoding_N>`                                                                                                                                                                                                                                                                                     |
| `Tuple(name1 T1, ..., nameN TN)`                                                                          | `0x20<var_uint_number_of_elements><var_uint_name_size_1><name_data_1><nested_type_encoding_1>...<var_uint_name_size_N><name_data_N><nested_type_encoding_N>`                                                                                                                                                                                                               |
| `Set`                                                                                                     | `0x21`                                                                                                                                                                                                                                                                                                                                                                     |
| `Interval`                                                                                                | `0x22<interval_kind>` (see [interval kind binary encoding](#interval-kind-binary-encoding))                                                                                                                                                                                                                                                                                |
| `Nullable(T)`                                                                                             | `0x23<nested_type_encoding>`                                                                                                                                                                                                                                                                                                                                               |
| `Function`                                                                                                | `0x24<var_uint_number_of_arguments><argument_type_encoding_1>...<argument_type_encoding_N><return_type_encoding>`                                                                                                                                                                                                                                                          |
| `AggregateFunction(function_name(param_1, ..., param_N), arg_T1, ..., arg_TN)`                            | `0x25<var_uint_version><var_uint_function_name_size><function_name_data><var_uint_number_of_parameters><param_1>...<param_N><var_uint_number_of_arguments><argument_type_encoding_1>...<argument_type_encoding_N>` (see [aggregate function parameter binary encoding](#aggregate-function-parameter-binary-encoding))                                                     |
| `LowCardinality(T)`                                                                                       | `0x26<nested_type_encoding>`                                                                                                                                                                                                                                                                                                                                               |
| `Map(K, V)`                                                                                               | `0x27<key_type_encoding><value_type_encoding>`                                                                                                                                                                                                                                                                                                                             |
| `IPv4`                                                                                                    | `0x28`                                                                                                                                                                                                                                                                                                                                                                     |
| `IPv6`                                                                                                    | `0x29`                                                                                                                                                                                                                                                                                                                                                                     |
| `Variant(T1, ..., TN)`                                                                                    | `0x2A<var_uint_number_of_variants><variant_type_encoding_1>...<variant_type_encoding_N>`                                                                                                                                                                                                                                                                                   |
| `Dynamic(max_types=N)`                                                                                    | `0x2B<uint8_max_types>`                                                                                                                                                                                                                                                                                                                                                    |
| `Custom type` (`Ring`, `Polygon`, etc)                                                                    | `0x2C<var_uint_type_name_size><type_name_data>`                                                                                                                                                                                                                                                                                                                            |
| `Bool`                                                                                                    | `0x2D`                                                                                                                                                                                                                                                                                                                                                                     |
| `SimpleAggregateFunction(function_name(param_1, ..., param_N), arg_T1, ..., arg_TN)`                      | `0x2E<var_uint_function_name_size><function_name_data><var_uint_number_of_parameters><param_1>...<param_N><var_uint_number_of_arguments><argument_type_encoding_1>...<argument_type_encoding_N>` (see [aggregate function parameter binary encoding](#aggregate-function-parameter-binary-encoding))                                                                       |
| `Nested(name1 T1, ..., nameN TN)`                                                                         | `0x2F<var_uint_number_of_elements><var_uint_name_size_1><name_data_1><nested_type_encoding_1>...<var_uint_name_size_N><name_data_N><nested_type_encoding_N>`                                                                                                                                                                                                               |
| `JSON(max_dynamic_paths=N, max_dynamic_types=M, path Type, SKIP skip_path, SKIP REGEXP skip_path_regexp)` | `0x30<uint8_serialization_version><var_int_max_dynamic_paths><uint8_max_dynamic_types><var_uint_number_of_typed_paths><var_uint_path_name_size_1><path_name_data_1><encoded_type_1>...<var_uint_number_of_skip_paths><var_uint_skip_path_size_1><skip_path_data_1>...<var_uint_number_of_skip_path_regexps><var_uint_skip_path_regexp_size_1><skip_path_data_regexp_1>...` |

For type `JSON` byte `uint8_serialization_version` indicates the version of the serialization. Right now the version is always 0 but can change in future if new arguments will be introduced for `JSON` type.

### Interval kind binary encoding

The table below describes how different interval kinds of `Interval` data type are encoded.

| Interval kind | Binary encoding |
|---------------|-----------------|
| `Nanosecond`  | `0x00`          |
| `Microsecond` | `0x01`          |
| `Millisecond` | `0x02`          |
| `Second`      | `0x03`          |
| `Minute`      | `0x04`          |
| `Hour`        | `0x05`          |
| `Day`         | `0x06`          |
| `Week`        | `0x07`          |
| `Month`       | `0x08`          |
| `Quarter`     | `0x09`          |
| `Year`        | `0x1A`          |

### Aggregate function parameter binary encoding

The table below describes how parameters of `AggragateFunction` and `SimpleAggregateFunction` are encoded.
The encoding of a parameter consists of 1 byte indicating the type of the parameter and the value itself.

| Parameter type           | Binary encoding                                                                                                                |
|--------------------------|--------------------------------------------------------------------------------------------------------------------------------|
| `Null`                   | `0x00`                                                                                                                         |
| `UInt64`                 | `0x01<var_uint_value>`                                                                                                         |
| `Int64`                  | `0x02<var_int_value>`                                                                                                          |
| `UInt128`                | `0x03<uint128_little_endian_value>`                                                                                            |
| `Int128`                 | `0x04<int128_little_endian_value>`                                                                                             |
| `UInt128`                | `0x05<uint128_little_endian_value>`                                                                                            |
| `Int128`                 | `0x06<int128_little_endian_value>`                                                                                             |
| `Float64`                | `0x07<float64_little_endian_value>`                                                                                            |
| `Decimal32`              | `0x08<var_uint_scale><int32_little_endian_value>`                                                                              |
| `Decimal64`              | `0x09<var_uint_scale><int64_little_endian_value>`                                                                              |
| `Decimal128`             | `0x0A<var_uint_scale><int128_little_endian_value>`                                                                             |
| `Decimal256`             | `0x0B<var_uint_scale><int256_little_endian_value>`                                                                             |
| `String`                 | `0x0C<var_uint_size><data>`                                                                                                    |
| `Array`                  | `0x0D<var_uint_size><value_encoding_1>...<value_encoding_N>`                                                                   |
| `Tuple`                  | `0x0E<var_uint_size><value_encoding_1>...<value_encoding_N>`                                                                   |
| `Map`                    | `0x0F<var_uint_size><key_encoding_1><value_encoding_1>...<key_endoding_N><value_encoding_N>`                                   |
| `IPv4`                   | `0x10<uint32_little_endian_value>`                                                                                             |
| `IPv6`                   | `0x11<uint128_little_endian_value>`                                                                                            |
| `UUID`                   | `0x12<uuid_value>`                                                                                                             |
| `Bool`                   | `0x13<bool_value>`                                                                                                             |
| `Object`                 | `0x14<var_uint_size><var_uint_key_size_1><key_data_1><value_encoding_1>...<var_uint_key_size_N><key_data_N><value_encoding_N>` |
| `AggregateFunctionState` | `0x15<var_uint_name_size><name_data><var_uint_data_size><data>`                                                                |
| `Negative infinity`      | `0xFE`                                                                                                                         |
| `Positive infinity`      | `0xFF`                                                                                                                         |
