ExaLogLog (Ertl, EDBT 2025) reaches the same RMSE as 6-bit HyperLogLog with around 43% less memory. Today I'm releasing a from-scratch pure-Rust implementation: both variants the paper recommends, both estimators, lock-free concurrent ingest, sparse mode, optional serde/rayon/SIMD features, and a byte-for-byte parity test against the Dynatrace Java reference.