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Hi, is it possible to override serializer?  I have a library class annotated as `@Serializable` but I would like to use different serializer than default one but I can't change the library code.

Depends a bit on your use case. You can always specify the serializer explicitly when encoding/decoding if it's the immediate element you're trying to encode/decode. If it's nested in a structure you don't control it gets trickier..

see <https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md#serializing-3rd-party-classes>

I can't set serializer when calling encode, I don't call it directly

if the library class is nested in a structure you own you could override it that way, see: <https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md#specifying-serializer-on-a-property>

Are you using some framework which performs the serialization then?

Ktor &amp; Kmongo, both use kotlinx.serialization

I'm not aware of any explicit ways to set the serializer of a specific class when constructing `Json` serializer sadly..  Could've been handy in this case? :slightly_smiling_face:
```Json {
  useSerializerForClass&lt;MyLibClass&gt;(CustomLibSerializer)
}```
Perhaps there's some GH issue for it

It would be great! Even better if it was possible to set it in serializer module

Let me know if you find or create an issue.. I'd add a thumbs up to it :blob-joy:

<https://github.com/Kotlin/kotlinx.serialization/issues/1952>

the serialization format has influence over `@Contextual` and `@Polymorphic` serialization because the containing classes' serializers look up the members' serializers via `serializersModule`, but that's not true for other members. serializers for generics are passed as constructor parameters and all others are referenced directly, the serial format has no influence over that.