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@swankjesse @ZacSweers @JakeWharton @NightlyNexus @vanniktech

Change Log

Version 1.14.0

Version 1.13.0


  • New: Support for Kotlin Symbol Processing (KSP). KSP is an alternative to annotation processing code gen. It's builds faster and better supports Kotlin language features.

    To use KSP in your application you must enable the KSP Gradle plugin and add a KSP dependency on Moshi codegen.

    plugins {
    dependencies {

    If you're switching from annotation processing (kapt) to KSP, you should remove the kapt plugin and the kapt Moshi dependency.

  • New: @Json(ignore = true) is a Moshi-specific way to exclude properties from JSON encoding and decoding.

  • New: Support Java 16 records. (Moshi still requires Java 8 only; we're shipping a multi-release jar to better support modern JVMs.)

  • New: Option to disable generating R8/ProGuard files. These files prevent code shrinkers from removing files that support JSON processing. If you're not using ProGuard or R8, you can skip this step.

    ksp {
      arg("moshi.generateProguardRules", "false")
  • Upgrade: Kotlin 1.6.0.

Version 1.12.0


  • New: Improve generated code performance when all properties are set.
  • Fix: Don't crash on a missing type element like @SuppressLint.
  • Fix: Update the JVM metadata library to avoid problems on Kotlin 1.5.0-M2.
  • Fix: Support generic arrays with defaults in generated adapters.
  • Fix: Don't generate code with simple name collisions.
  • Upgrade: Okio 2.10.0.
  • Upgrade: Kotlin 1.4.31.

Version 1.11.0


  • New: Kotlin extension functions and properties. Use of these extensions is only possible from Kotlin, and requires the Kotlin stdlib dependency. This release does not have any Kotlin requirement and can be used Kotlin-free from Java.

    /** Extension alternative to [Types.nextAnnotations()]. */
    fun <reified T : Annotation> Set<Annotation>.nextAnnotations(): Set<Annotation>?
    /** Extension alternative to [Types.getRawType()]. */
    val Type.rawType: Class<*>
    /** Extension alternative to [Types.arrayOf()]. */
    fun KClass<*>.asArrayType(): GenericArrayType
    /** Extension alternative to [Types.arrayOf()]. */
    fun Type.asArrayType(): GenericArrayType
  • New: Experimental Kotlin extensions. These depend on unreleased APIs and may break in a future release of Kotlin. If you are comfortable with this, add @ExperimentalStdlibApi at the callsite or add this argument to your Kotlin compiler: "-Xopt-in=kotlin.ExperimentalStdlibApi".

    /** Returns the adapter for [T]. */
    inline fun <reified T> Moshi.adapter(): JsonAdapter<T>
    /** Returns the adapter for [ktype]. */
    fun <T> Moshi.adapter(ktype: KType): JsonAdapter<T>
    /** Adds an adapter for [T]. */
    inline fun <reified T> Moshi.Builder.addAdapter(adapter: JsonAdapter<T>): Moshi.Builder
    /** Extension alternative to [Types.arrayOf()]. */
    fun KType.asArrayType(): GenericArrayType
    /** Extension alternative to [Types.subtypeOf()]. */
    inline fun <reified T> subtypeOf(): WildcardType
    /** Extension alternative to [Types.supertypeOf()]. */
    inline fun <reified T> supertypeOf(): WildcardType
  • New: JsonReader.nextSource(). This returns an Okio BufferedSource that streams the UTF-8 bytes of a JSON value. Use this to accept JSON values without decoding them, to delegate to another JSON processor, or for streaming access to very large embedded values.

  • New: Moshi.Builder.addLast(). Use this when installing widely-applicable adapter factories like KotlinJsonAdapterFactory. Adapters registered with add() are preferred (in the order they were added), followed by all adapters registered with addLast() (also in the order they were added). This precedence is retained when Moshi.newBuilder() is used.

  • New: setTag(), tag() methods on JsonReader and JsonWriter. Use these as a side-channel between adapters and their uses. For example, a tag may be used to track use of unexpected data in a custom adapter.

  • Fix: Don't crash with a StackOverflowError decoding backward-referencing type variables in Kotlin. This caused problems for parameterized types like MyInterface<E : Enum<E>>.

  • Upgrade: Okio 1.17.5.

  • Upgrade: Kotlin 1.4.10.

Version 1.10.0


  • New: Upgrade to Kotlin 1.4.0.
  • New: JsonReader.promoteNameToValue() makes it easier to build custom Map adapters.
  • New: Options.strings().
  • New: PolymorphicJsonAdapterFactory.withFallbackJsonAdapter() makes it possible to handle unrecognized types when encoding and decoding.
  • New: Add JsonWriter.jsonValue API
  • New: Code gen now generates precise proguard rules on-the-fly.
  • New: Improve error when incorrectly trying to use a collection class like ArrayList instead of List
  • Fix: Prevent R8 from keeping all @Metadata annotations
  • Fix: Avoid VerifyErrors on Android 4.4 devices when using R8
  • Fix: Fix resolution of types in superclass settable properties

Version 1.9.3


  • Fix: Tweak a shrinker rule to mitigate an R8 bug which was causing classes unrelated to the Kotlin adpater code generation to be retained.
  • Fix: Ensure that the Kotlin adapter code generation does not line wrap in the middle of a string if your JSON keys contain spaces.
  • Fix: Strip type annotations before emitting type references like Foo::class in the Kotlin adapter code generation.
  • Fix: Separate the runtime check for Kotlin's DefaultConstructorMarker from the check for Metadata. A shrinker may have removed Metadata and we should still check for DefaultConstructorMarker.

Version 1.9.2


  • Fix: Generate correct adapters for several special cases including reified inline types, public classes enclosed in internal classes, deprecated types with -Werror, primitives in type parameters, nullables in type parameters, and type aliases in type parameters.

Version 1.9.1


  • Fix: "abstract function ... cannot have code" code gen crash when parsing Kotlin metadata.
  • Fix: Generate code to support constructors with more than 32 parameters. The 1.9.0 release had a regression where classes with 33+ parameters would crash upon decoding.
  • Fix: Generate code to support more constructor cases, such as classes with non-property parameters and classes with multiple constructors.
  • Fix: Generate code to handle type aliases in type parameters.

Version 1.9.0


  • This release requires kotlin-reflect or moshi-kotlin-codegen for all Kotlin classes.

    Previously Moshi wouldn't differentiate between Kotlin classes and Java classes if Kotlin was not configured. This caused bad runtime behavior such as putting null into non-nullable fields! If you attempt to create an adapter for a Kotlin type, Moshi will throw an IllegalArgumentException.

    Fix this with either the reflection adapter:

    val moshi = Moshi.Builder()
        // ... add your own JsonAdapters and factories ...

    Or the codegen annotation processor:

    @JsonClass(generateAdapter = true)
    data class BlackjackHand(
            val hidden_card: Card,
            val visible_cards: List<Card>

    The Kotlin documentation explains the required build configuration changes.

  • New: Change how Moshi's generated adapters call constructors. Previous generated code used a combination of the constructor and copy() method to set properties that have default values. With this update we call the same synthetic constructor that Kotlin uses. This is less surprising though it requires us to generate some tricky code.

  • New: Make Rfc3339DateJsonAdapter null-safe. Previously Moshi would refuse to decode null dates. Restore that behavior by explicitly forbidding nulls with Rfc3339DateJsonAdapter().nonNull().

  • New: Require Kotlin 1.3.50 or newer.

  • New: JsonWriter.valueSink() streams JSON-formatted data inline. Use this to do basic includes of raw JSON within a streamed document.

  • New: Support Gradle incremental processing in code gen.

  • New: Improve error messages. This includes better errors when field names and JSON names disagree, and when failing on an unknown field.

  • New: Support default values in PolymorphicJsonAdapterFactory.

  • New: Permit multiple labels for each subtype in PolymorphicJsonAdapterFactory. The first label is used when writing an object to JSON.

  • New: Forbid automatic encoding of platform classes in kotlinx. As with java.*, android.*, and kotlin.* Moshi wants you to specify how to encode platform types.

  • New: @JsonClass(generator=...) makes it possible for third-party libraries to provide generated adapters when Moshi's default adapters are insufficient.

  • Fix: Simplify wildcard types like List<? extends Number> to their base types List<Number> when finding type adapters. This is especially useful with Kotlin where wildcards may be added automatically.

  • Fix: Use the correct name when the @Json annotation uses field targeting like @field:Json.

  • Fix: Support multiple transient properties in KotlinJsonAdapter.

  • Fix: Don't explode attempting to resolve self-referential type variables like in Comparable<T extends Comparable<T>>.

  • Fix: Don't infinite loop on skipValue() at the end an object or array. Also disallow calling skipValue() at the end of a document.

Version 1.8.0


  • New: Support JSON objects that include type information in the JSON. The new PolymorphicJsonAdapterFactory writes a type field when encoding, and reads it when decoding.

  • New: Fall back to the reflection-based KotlinJsonAdapterFactory if it is enabled and a generated adapter is not found. This makes it possible to use reflection-based JSON adapters in development (so you don't have to wait for code to be regenerated on every build) and generated JSON adapters in production (so you don't need the kotlin-reflect library).

  • New: The peekJson() method on JsonReader let you read ahead on a JSON stream without consuming it. This builds on Okio's new Buffer.peek() API.

  • New: The beginFlatten() and endFlatten() methods on JsonWriter suppress unwanted nesting when composing adapters. Previously it was necessary to flatten objects in memory before writing.

  • New: Upgrade to Okio 1.16.0. We don't yet require Kotlin-friendly Okio 2.1 but Moshi works fine with that release.

  • Fix: Don't return partially-constructed adapters when using a Moshi instance concurrently.

  • Fix: Eliminate warnings and errors in generated .kt triggered by type variance, primitive types, and required values.

  • Fix: Improve the supplied rules ( to better retain symbols used by Moshi. We recommend R8 when shrinking code.

  • Fix: Remove code generation companion objects. This API was neither complete nor necessary.

Version 1.7.0


  • New: EnumJsonAdapter makes it easy to specify a fallback value for unknown enum constants. By default Moshi throws an JsonDataException if it reads an unknown enum constant. With this you can specify a fallback value or null.

    new Moshi.Builder()

    Note that this adapter is in the optional moshi-adapters module.

    implementation 'com.squareup.moshi:moshi-adapters:1.7.0'
  • New: Embed R8/ProGuard rules in the .jar file.

  • New: Use @CheckReturnValue in more places. We hope this will encourage you to use skipName() instead of nextName() for better performance!

  • New: Forbid automatic encoding of platform classes in androidx. As with java.*, android.*, and kotlin.* Moshi wants you to specify how to encode platform types.

  • New: Improve error reporting when creating an adapter fails.

  • New: Upgrade to Okio 1.15.0. We don't yet require Kotlin-friendly Okio 2.x but Moshi works fine with that release.

    implementation 'com.squareup.okio:okio:1.15.0'
  • Fix: Return false from JsonReader.hasNext() at document's end.

  • Fix: Improve code gen to handle several broken cases. Our generated adapters had problems with nulls, nested parameterized types, private transient properties, generic type aliases, fields with dollar signs in their names, and named companion objects.

Version 1.6.0


  • Moshi now supports codegen for Kotlin. We've added a new annotation processor that generates a small and fast JSON adapter for your Kotlin types. It can be used on its own or with the existing KotlinJsonAdapterFactory adapter.

  • Moshi now resolves all type parameters. Previously Moshi wouldn't resolve type parameters on top-level classes.

  • New: Support up to 255 levels of nesting when reading and writing JSON. Previously Moshi would reject JSON input that contained more than 32 levels of nesting.

  • New: Write encoded JSON to a stream with JsonWriter.value(BufferedSource). Use this to emit a JSON value without decoding it first.

  • New: JsonAdapter.nonNull() returns a new JSON adapter that forbids explicit nulls in the JSON body. Use this to detect and fail eagerly on unwanted nulls.

  • New: JsonReader.skipName() is like nextName() but it avoids allocating when a name is unknown. Use this when JsonReader.selectName() returns -1.

  • New: Automatic module name of com.squareup.moshi for use with the Java Platform Module System. This moves moshi-adapters into its own .adapters package and forwards the existing adapter. It moves the moshi-kotlin into its own .kotlin.reflect package and forwards the existing adapter.

  • New: Upgrade to Okio 1.14.0.

  • Fix: Fail fast if there are trailing non-whitespace characters in the JSON passed to JsonAdapter.fromJson(String). Previously such data was ignored!

  • Fix: Fail fast when Kotlin types are abstract, inner, or object instances.

  • Fix: Fail fast if name() is called out of sequence.

  • Fix: Handle asymmetric Type.equals() methods when doing type comparisons. Previously it was possible that a registered type adapter would not be used because its Type.equals() method was not consistent with a user-provided type.

  • Fix: JsonValueReader.selectString() now returns -1 for non-strings instead of throwing.

  • Fix: Permit reading numbers as strings when the JsonReader was created from a JSON value. This was always supported when reading from a stream but broken when reading from a decoded value.

  • Fix: Delegate to user-adapters in the adapter for Object.class. Previously when Moshi encountered an opaque Object it would only use the built-in adapters. With this change user-installed adapters for types like String will always be honored.

Version 1.5.0


  • Moshi now uses @Nullable to annotate all possibly-null values. We've added a compile-time dependency on the JSR 305 annotations. This is a provided dependency and does not need to be included in your build configuration, .jar file, or .apk. We use @ParametersAreNonnullByDefault and all parameters and return types are never null unless explicitly annotated @Nullable.

  • Warning: Moshi APIs in this update are source-incompatible for Kotlin callers. Nullability was previously ambiguous and lenient but now the compiler will enforce strict null checks.

  • Kotlin models are now supported via the moshi-kotlin extension. KotlinJsonAdapterFactory is the best way to use Kotlin with Moshi. It honors default values and is null-safe. Kotlin users that don't use this factory should write custom adapters for their JSON types. Otherwise Moshi cannot properly initialize delegated properties of the objects it decodes.

  • New: Upgrade to Okio 1.13.0.

  • New: You may now declare delegates in @ToJson and @FromJson methods. If one of the arguments to the method is a JsonAdapter of the same type, that will be the next eligible adapter for that type. This may be useful for composing adapters.

  • New: Types.equals(Type, Type) makes it easier to compare types in JsonAdapter.Factory.

  • Fix: Retain the sign on negative zero.

Version 1.4.0


Moshi 1.4 is a major release that adds JSON values as a core part of the library. We consider any Java object comprised of maps, lists, strings, numbers, booleans and nulls to be a JSON value. These are equivalent to parsed JSON objects in JavaScript, Gson’s JsonElement, and Jackson’s JsonNode. Unlike Jackson and Gson, Moshi just uses Java’s built-in types for its values:

JSON typeJava type
{...}ObjectMap<String, Object>
123NumberDouble, Long, or BigDecimal

Moshi's new API JsonAdapter.toJsonValue() converts your application classes to JSON values comprised of the above types. Symmetrically, JsonAdapter.fromJsonValue() converts JSON values to your application classes.

  • New: JsonAdapter.toJsonValue() and fromJsonValue().
  • New: JsonReader.readJsonValue() reads a JSON value from a stream.
  • New: Moshi.adapter(Type, Class<? extends Annotation>) lets you look up the adapter for a qualified type.
  • New: JsonAdapter.serializeNulls() and indent() return JSON adapters that customize the format of the encoded JSON.
  • New: JsonReader.selectName() and selectString() optimize decoding JSON with known names and values.
  • New: Types.nextAnnotations() reduces the amount of code required to implement a custom JsonAdapter.Factory.
  • Fix: Don't fail on large longs that have a fractional component like 9223372036854775806.0.

Version 1.3.1


  • Fix: Don't incorrectly report invalid input when a slash character is escaped. When we tightened our invalid escape handling we missed the one character that is valid both escaped \/ and unescaped /.

Version 1.3.0


  • New: Permit @ToJson and @FromJson methods to take any number of JsonAdapter parameters to delegate to. This is supported for @ToJson methods that take a JsonWriter and @FromJson methods that take a JsonReader.

  • New: Throw JsonEncodingException when the incoming data is not valid JSON. Use this to differentiate data format problems from connectivity problems.

  • New: Upgrade to Okio 1.11.0.

  • New: Omit Kotlin (kotlin.*) and Scala (scala.*) platform types when encoding objects using their fields. This should make it easier to avoid unexpected dependencies on platform versions.

  • Fix: Explicitly limit reading and writing to 31 levels of nested structure. Previously no specific limit was enforced, but deeply nested documents would fail with either an ArrayIndexOutOfBoundsException due to a bug in JsonWriter's path management, or a StackOverflowError due to excessive recursion.

  • Fix: Require enclosed types to specify their enclosing type with Types.newParameterizedTypeWithOwner(). Previously this API did not exist and looking up adapters for enclosed parameterized types was not possible.

  • Fix: Fail on invalid escapes. Previously any character could be escaped. With this fix only characters permitted to be escaped may be escaped. Use JsonReader.setLenient(true) to read JSON documents that escape characters that should not be escaped.

Version 1.2.0


  • New: Take advantage of Okio's new Options feature when reading field names and enum values. This has a significant impact on performance. We measured parsing performance improve from 89k ops/sec to 140k ops/sec on one benchmark on one machine.

  • New: Upgrade to Okio 1.8.0.

  • New: Support types that lack no-argument constructors objects on Android releases prior to Gingerbread.

  • Fix: Add writer value overload for boxed booleans. Autoboxing resolves boxed longs and doubles to value(Number), but a boxed boolean would otherwise resolve to value(boolean) with an implicit call to booleanValue() which has the potential to throw NPEs.

  • Fix: Be more aggressive about canonicalizing types.

Version 1.1.0


  • New: Support RFC 7159, the latest JSON specification. This removes the constraint that the root value must be an array or an object. It may now take any value: array, object, string, number, boolean, or null. Previously this was only permitted if the adapter was configured to be lenient.
  • New: Enum constants may be annotated with @Json to customize their encoded value.
  • New: Create new builder from Moshi instance with Moshi.newBuilder().
  • New: Types.getRawType() and Types.collectionElementType() APIs to assist in defining generic type adapter factories.

Version 1.0.0


  • API Change: Replaced new JsonReader() with JsonReader.of() and new JsonWriter() with JsonWriter.of(). If your code calls either of these constructors it will need to be updated to call the static factory method instead.
  • API Change: Don’t throw IOException on JsonAdapter.toJson(T). Code that calls this method may need to be fixed to no longer catch an impossible IOException.
  • Fix: the JSON adapter for Object no longer fails when encountering null in the stream.
  • New: @Json annotation can customize a field's name. This is particularly handy for fields whose names are Java keywords, like default or public.
  • New: Rfc3339DateJsonAdapter converts between a java.util.Date and a string formatted with RFC 3339 (like 2015-09-26T18:23:50.250Z). This class is in the new moshi-adapters subproject. You will need to register this adapter if you want this date formatting behavior. See it in action in the dates example.
  • New: Moshi.adapter() keeps a cache of all created adapters. For best efficiency, application code should keep a reference to required adapters in a field.
  • New: The Types factory class makes it possible to compose types like List<Card> or Map<String, Integer>. This is useful to look up JSON adapters for parameterized types.
  • New: JsonAdapter.failOnUnknown() returns a new JSON adapter that throws if an unknown value is encountered on the stream. Use this in development and debug builds to detect typos in field names. This feature shouldn’t be used in production because it makes migrations very difficult.

Version 0.9.0


  • Databinding for primitive types, strings, enums, arrays, collections, and maps.
  • Databinding for plain old Java objects.
  • JSONPath support for both JsonReader and JsonWriter.
  • Throw JsonDataException when there’s a data binding problem.
  • Adapter methods: @ToJson and @FromJson.
  • Qualifier annotations: @JsonQualifier to permit different type adapters for the same Java type.
  • Imported code from Gson: JsonReader, JsonWriter. Also some internal classes: LinkedHashTreeMap for hash-collision avoidance and Types for typesafe databinding.