Choosing a Rails JSON serializer for your API in 2021

The state of JSON serialization in the Rails world seems to change fast and often. A few years back most developers advised you to use ActiveModelSerializers if you cared about speed, but most of them have since considered the project dead because the last release was in 2015. Furthermore it seems Netflix stopped maintaining the Fast JSON API gem while the RABL gem hasn’t seen any releases since 2018. So what would I pick when building a new API in Ruby on Rails in 2021?


On of the most common known gems to serialize objects into JSON is probably Jbuilder. Developed by the authors of Rails and it is even mentioned in a Gemfile comment for new Rails projects. Last release at the time of this writing was in September 2020. Serialization is configured in views with a simple but flexible DSL. You can generate any JSON structure you like using this gem. For simple API’s this works fine while rendering speed still seems to be ok. All in all a solid choice for a new API that doesn’t have too much data or users yet. Find out more about it on their Github page.

JSON:API Serializer

A fork of the original Fast JSON API project that was started by Netflix. When they stopped maintaining it some community members stepped up and continued the project under this name. If you want to conform to the JSON:API specification and care about speed, this is probably your most solid choice. Last release at the time of this writing was in August 2020. Find out more about it on their Github page.


A newcomer to the scene! It’s always great when people step up to fill a gap. This is my personal favorite because it gives you the nice DSL with serializers (Blueprints) that I’ve known from ActiveModelSerializers and Fast JSON API, while allowing you to render any JSON structure without giving up speed. If you expect your API to see lots of traffic you should definitely consider using this gem. Last release at the time of this writing was in November 2020. Find out more about it on their Github page.

After you deploy the API

I’ve experienced quite some weird issues after deploying Rails JSON API’s. Sometimes it can be a blackbox to debug, especially for web applications with lots of users. Following the access logs is not going to give you the insight you need when debugging high load, timeouts or other problems. I’m building a service to help you get insight into the usage and abuse of your web API, a sort of Analytics for API’s. My newly launched company Webindie will be the sole owner and the product is now open for sign ups. Leave your email below if you’re interested in updates about it.

Don’t hesitate to contact me on Twitter if you have any questions or comments about this post or my new company.