Armin Ronacher ships Deser, an experimental Rust serialization library to fix Serde's pain points
mitsuhiko · x · 2026-09-30
Armin Ronacher (mitsuhiko) published a long-form writeup on Deser, his new experimental Rust serialization library built to address long-standing Serde limitations.
Pain points he details:
- Arbitrarily precise numbers interact badly with internally tagged enums under serde's arbitraryprecision feature: in-band signalling via a magic-key map breaks enum buffering, and Cargo feature unification means any dependency can trigger it.
- #[serde(flatten)] breaks integer map keys, since buffered values keep JSON keys as strings ("42" fails to parse as u32).
Deser features its own data model (including arbitrary-precision numbers), a modular multi-format crate layout (JSON, CBOR, MessagePack, TOML, YAML, XML, and more), location tracking, validation, and a deser-serde bridge. He also explains why replacing Serde is hard given its ecosystem dominance. The repo is open source on GitHub.
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