If I understand this correctly, this section only makes sense when creating a custom normalizer (as the build-in normalizers already implement this). Is there a reason to keep this section in /serializer, or should we instead only put it in /serializer/custom_normalizers?

Indeed yes, after it's always interesting to know it. Tell me, what do you prefer?

@wouterj what would you like to do with this ? move all in the custom normalizer or keep it as it is ?

Sorry, I somehow missed your reaction. Yes, I'm in favor of moving the performance section to the custom normalizer article.

Maxime, thanks for improving this. I'm sorry it took us so long to merge.