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Taoensso open source
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The fastest serialization library for Clojure

Clojure's rich data types are awesome. And its reader allows you to take your data just about anywhere. But the reader can be painfully slow when you've got a lot of data to crunch (like when you're serializing to a database).

Nippy is an attempt to provide a reliable, high-performance drop-in alternative to the reader.

Used by Carmine, Faraday, PigPen, Onyx, XTDB, Datalevin, and others.

Latest release/s

  • 2022-07-18 3.2.0 (stable): changes
  • 2023-09-25 3.3.0-RC2 (upcoming): changes
  • 2023-09-26 3.4.0-beta1 (dev): changes

Main tests Graal tests

See here for earlier releases.

Why Nippy?

  • Small, simple all-Clojure library
  • Terrific performance: the best for Clojure that I'm aware of
  • Comprehensive support for all standard data types
  • Easily extendable to custom data types
  • Robust test suite, incl. full coverage for every supported type
  • Auto fallback to Java Serializable when available
  • Auto fallback to Clojure Reader for all other types (including tagged literals
  • Pluggable compression with built-in LZ4, Zstandard, etc.
  • Pluggable encryption with built-in AES128
  • Tools for easy + robust integration into 3rd-party libraries, etc.
  • Powerful thaw transducer for flexible data inspection and transformation


Since its earliest versions, Nippy has consistently been the fastest serialization library for Clojure that I'm aware of. It offers:

  • Roundtrip times >12x faster than tools.reader with 60% smaller data size.
  • Roundtrip times >2x faster than data.fressian with 30% smaller data size.


The benchmark code can be easily run in your own environment.



You can help support continued work on this project, thank you!! 🙏


Copyright © 2012-2023 Peter Taoussanis.
Licensed under EPL 1.0 (same as Clojure).