strum

strum is the single most popular Rust enum ergonomics crate, with 100M+ all-time downloads. It provides derive macros that cover the most common enum boilerplate: Display, FromStr, iteration, counting, metadata, discriminant extraction, and integer conversion — what would otherwise require five separate dependencies.

Key derives

• Display / AsRefStr — convert variants to strings with configurable casing and formatting
• EnumString (FromStr) — parse strings into enum variants
• EnumIter — iterate all variants of a fieldless or unit-variant enum
• EnumCount — const COUNT: usize for the number of variants
• EnumProperty — attach custom key-value metadata per variant via #[strum(props(key = "value"))]
• EnumDiscriminants — generate a separate fieldless "kind" enum mirroring the data-carrying one
• EnumIs — is_variant() methods for each variant
• FromRepr — convert integers to enum variants (safer than as casting)

When to use strum

strum is the default choice when you need any combination of enum-to-string, string-to-enum, or variant iteration. For error types specifically, thiserror or snafu are better fits. For broader trait derivation beyond enums (From, Into, operators), derive-more covers more ground. For bitflag-style enums, bitflags is the standard.

enum-iterator offers a richer iteration API than strum's EnumIter (cyclic navigation, next()/previous(), works on composite types), but strum's bundled approach is usually sufficient. strum-lite provides a lighter alternative using declarative macros for faster compilation.

See rust-enum-crates for the full landscape.