GoKawiilArmin Ronacher unveils Deser, a new Rust serialization library challenging Serde
Developer Armin Ronacher has published a project called Deser, aiming to address longstanding limitations in Rust's dominant Serde serialization library. He details specific bugs and edge cases in Serde, including failures when combining internally tagged enums with arbitrary-precision numbers, broken integer key handling under field flattening, and deserializer adapters that don't compose properly.
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Serde's near-universal adoption across the Rust ecosystem means these edge cases can surface unpredictably whenever crates enable conflicting features, since Cargo unifies feature flags across a dependency graph. Ronacher's critique suggests that fixing these issues within Serde's existing architecture may be difficult, which could be part of the motivation for building an alternative rather than patching the incumbent library. Any serious challenger to Serde would need to prove it can match its maturity and ecosystem support before gaining meaningful adoption.
- Deser is a newly announced Rust serialization library positioned as a rethink of Serde's design.
- Serde's data model struggles with cases like arbitrary-precision numbers in internally tagged enums and integer keys under field flattening.
- Cargo's feature unification means a single dependency enabling a feature like arbitrary_precision can cause unexpected failures elsewhere in a project.
Source: lucumr.pocoo.org, 2026-09-29
Published there as: “Deser: Rethinking Rust Serialization”
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