Rails 7.2 Unveiled: YJIT Default, DevContainers & Performance Boosts

Ruby on Rails 7.2 has been released, featuring YJIT (Yet another JIT) enabled by default and automatic generation of development containers.

The minimum required Ruby version is now 3.1, and to use YJIT as the default you need Ruby 3.3 or newer.

YJIT was developed by GitHub and Shopify’s Ruby team, originating in 2019, initially written in C and later ported to Rust for improved safety and tooling.

According to Shopify engineers, YJIT in Ruby 3.2 delivers a 38% speed increase over the interpreter, though memory usage concerns remain.

The Rails team promises a 15‑25% reduction in latency, and the default Docker deployment includes jemalloc for optimized memory allocation.

The default Puma thread count has been lowered from 5 to 3 based on production experience, reducing potential adverse effects of too many threads.

Rails 7.2 also adds a devcontainer configuration that can be generated when creating a new app with rails new or adding to an existing app with rails devcontainer.

The default devcontainer includes a Redis container, a selectable database (SQLite, PostgreSQL, MySQL, or MariaDB), and a headless Chrome container, assuming use of VS Code with the Dev Containers extension.

This setup ensures consistent environments across teams and isolates development dependencies from the host system.

Additional features in the release note include blocking unsupported browsers and adding progressive web app support, allowing Rails apps to run with some desktop‑app capabilities.

Rails 7.2 also ships with Brakeman, a static analysis security tool, enabled by default.

Rails, created by David Heinemeier Hansson in 2004, follows the “convention over configuration” principle and uses ActiveRecord for rapid data‑driven web development.