free software, web technologies and heavy metal coding (and ruby of course)

Ruby serialization benchmark


Always use OJ for serialization (unless you’re using JRuby).

The longer version

The out-of-the-box solution for serialization in ruby is either the built-in JSON or the binary Marshal format. The former has the advantage that it’s a human readable, standardized and universal format, while the Marshal format is specific to ruby and not very human readable.

I was under the impression that the choice between those two was a decision between JSON and fast. For ruby’s core and standard library this is certainly true. But let’s have a closer look at the alternatives.

Standard types

--> Benchmarking an object of type Hash

     JSON (using oj):       68.3 i/s
         MessagePack:       62.7 i/s - 1.09x   slower
                BSON:       54.7 i/s - 1.25x   slower
             Marshal:       41.4 i/s - 1.65x   slower
   JSON (using Yajl):       31.3 i/s - 2.18x   slower
JSON (built-in ruby):       26.9 i/s - 2.54x   slower
                YAML:        1.2 i/s - 59.15x  slower

--> Benchmarking an object of type String

     JSON (using oj):      344.6 i/s
                BSON:      308.3 i/s - 1.12x   slower
             Marshal:      151.1 i/s - 2.28x   slower
         MessagePack:      127.8 i/s - 2.70x   slower
JSON (built-in ruby):       99.2 i/s - 3.47x   slower
   JSON (using Yajl):       96.9 i/s - 3.55x   slower
                YAML:        4.7 i/s - 74.01x  slower

--> Benchmarking an object of type Float

                BSON:      332.6 i/s
     JSON (using oj):      204.1 i/s - 1.63x   slower
             Marshal:      168.1 i/s - 1.98x   slower
         MessagePack:      124.3 i/s - 2.68x   slower
JSON (built-in ruby):       83.8 i/s - 3.97x   slower
   JSON (using Yajl):       80.2 i/s - 4.15x   slower
                YAML:        4.5 i/s - 73.27x  slower

So far OJ and BSON are the fast ones.

Any type

When evaluating a serializer it’s important that it’s a general purpose serializer, meaning that it can handle an arbitrary type without the need of modifying it. Most of the benchmarked serializers are eliminated by this requirement. The stereobooster/ruby-json-benchmark repository provides a nice overview of the capabilities of the different json implementations.

The next benchmark iteration focuses on the two fastest ones that can handle all types.

--> Benchmarking an object of type Float

     JSON (using oj):      198.8 i/s
             Marshal:      169.1 i/s - 1.18x  slower

--> Benchmarking an object of type Hash

     JSON (using oj):       70.9 i/s
             Marshal:       44.4 i/s - 1.60x  slower

--> Benchmarking an object of type String

     JSON (using oj):      368.0 i/s
             Marshal:      158.3 i/s - 2.33x  slower

--> Benchmarking an object of type CustomClass

     JSON (using oj):      195.2 i/s
             Marshal:       87.4 i/s - 2.23x  slower

Serializing a custom type is more than twice as fast with OJ than it is with Marshal.


Unless you are on JRuby I’d always use OJ. It is overall the fastest implementation and also provides the convenience of JSON. Additionally, if you’re using Ruby on Rails, you can use OJ as a drop in replacement for the standard implementation.


The benchmarks were made using benchmark-ips on a Lenovo X1 Carbon, Intel® Core™ i7-7600U CPU @ 2.80GHz, 16GB DDR3 RAM, running Ubuntu and running with ruby 2.5.0. Each iteration is performing a serialization and a subsequent deserialization.

The whole benchmark code is available as a gist.