High-performance JSON serializer/deserializer with zero extra allocations, zero-copy buffer wrapping, map/object inlining, polymorphic value-subclass support, and advanced parser hooks.
Fast and powerful implementation of JSON format for kotlinx-serialization.
kotlinx-serialization-json@Serializable sealed interface Base
@Serializable value class Foo(val int: Int): Base
val s = ZeroJson.encodeToString<Base>(Foo(42))
println(s)
// { "type": "Foo", "value": 42 }
println(ZeroJson.decodeFromString<Base>(s))
// 42
Setup Google repository (zero-json uses androidx.collection:collection under the hood):
repositories {
google()
}
zero-json-core)This option allows you to use all the features specific to zero-json.
implementation("io.github.adokky:zero-json-core:0.5.2")
zero-json-kotlinx)Compatible with kotlinx-serialization-json 1.9.0.
Not available for JavaScript, though WasmJs is supported.
implementation("io.github.adokky:zero-json-kotlinx:0.5.2")
Exclude the original kotlinx-serialization-json:
configurations.configureEach {
resolutionStrategy {
exclude("org.jetbrains.kotlinx", "kotlinx-serialization-json")
}
}
Both zero-json-core and zero-json-kotlinx can be used simultaneously.
StructureKind.MAP and StructureKind.CLASSQuick example:
Result:
{
"name": "Alex",
"age": 44,
zero-json is built for fast UTF-8 encoding/decoding — super common in network-related workloads. It's tuned for JVM backend services which handle tons of client requests, so serialization is one of the main bottlenecks. Client apps rarely hit serialization limits — they're more bogged down by UI or network delays.
Benchmarks use JMH, so results may vary on other platforms.
Decoding (smaller is better):
bytes_kotlinx 136.218 ± 1.453 us/op
bytes_zjson 107.799 ± 0.891 us/op
string_kotlinx 80.194 ± 0.751 us/op
string_zjson 100.707 ± 0.770 us/op
tree_kotlinx 42.197 ± 3.291 us/op
tree_zjson 28.922 ± 0.574 us/op
Encoding (smaller is better):
bytes_kotlinx 36.517 ± 0.587 us/op
bytes_zjson 29.325 ± 0.553 us/op
string_kotlinx 27.550 ± 0.635 us/op
string_zjson 42.241 ± 4.009 us/op
tree_kotlinx 31.760 ± 3.394 us/op
tree_zjson 19.541 ± 0.352 us/op
@JsonInline to inline its serialized form. Only final classes and Map instances can be inlined.ChunkedDecoder) and Float/Double types (still allocates much less than most serializers). On Kotlin/JS, it may allocate much more — not much we can do about it.Buffer interface that requires only size property and get method to be implemented.JsonReader). That allows implementing simple and efficient content-based polymorphism without extra allocations of JsonElement.The input JSON string must be fully loaded into memory before decoding. This library is not suitable for deserializing large JSON files. This limitation is irrelevant for typical REST APIs, where request and response sizes are limited
Duplicate JSON object keys are not allowed
On JS: no dynamic support
On JVM: Serialization using InputStream/OutputStream is not recommended. Nearly all I/O libraries and frameworks provide access to underlying array or buffer abstractions. Wrapping these is the intended way to use this library. For any streaming workload, we recommend using the original kotlinx-serialization-json instead.
No prettyPrint option
class Person(
val name: String,
val age: Int,
val location: Location,
val extra: Map<String, String>?,
)
class Location( val country: Country, val city: String)
class Country(
val name: String,
val code: Int
)
ZeroJson.encodeToString(
Person(
name = "Alex",
age = 44,
location = Location(
country = Country("Dreamland", 1234),
city = "SimCity"
),
extra = mapOf("avatar" to "https://cdn.example/profile_picture23535")
)
)
bytes:
decodeFromStream, encodeToStream (ByteArrayOutputStream/ByteArrayInputStream)decodeFromBuffer, encodeToBuffer (ArrayBuffer)string - decodeFromString, encodeToStringtree - decodeFromJsonElement, encodeToJsonElementSurfaced from shared tags and platforms — no rankings paid for.