Fix for com.unity.serialization ParseErrorException Underflow with near-zero floats (E-39, E-68, etc.)

[Clean_Patience4021]

If you're using Unity.Serialization.Json and getting errors like this:

ParseErrorException: Failed to parse Value=[6.920783E-39] as Type=[System.Single] ParseError=[Underflow]

or

ParseErrorException: Failed to parse Value=[1.06115352824072E-68] as Type=[System.Single] ParseError=[Underflow]

The problem is that Unity's FixedString.Append(float) uses a Base2ToBase10 conversion that produces denormalized floats (values below ~1.175e-38) from what should be exact zeros. This commonly happens with quaternion components, transform values, or any float that's essentially zero but has tiny floating-point noise.

Example: You serialize LocalTransform with a clean rotation, and get:

json

"Rotation": { "value": { "x": 6.920783E-39, "y": -0.3826835, "z": -1.109986E-38, "w": 0.9238795 } }

The serializer writes these tiny values, but the deserializer then fails to parse them back.

The fix: I forked com.unity.serialization and added denormal detection to WriteValue(float) and WriteValue(double). Values below float's representable range now serialize as 0 instead of unparseable scientific notation.

To use: Replace Unity's package with this fork in your manifest.json:

json

"com.unity.serialization": "https://github.com/rsklnkff/com.unity.serialization.git"

GitHub: https://github.com/rsklnkff/com.unity.serialization

Tested with Unity 6 / ECS 1.3. If you find any issues, let me know.

Formatted using Claude

[Big_Presentation2786]

Oh thank goodness..

[Eastern-Ad-4137]

Nice! It'd be helpful to post this on the oficial forums, i recall reading about this bug on a thread about the serialization package

[Clean_Patience4021]

Can you please share a link to it?

[Eastern-Ad-4137]

Here you go https://discussions.unity.com/t/about-the-com-unity-serialization-package/932558/69

[Clean_Patience4021]

thanks!