37signals Rails Best Practices

Comprehensive coding principles and conventions for Ruby on Rails applications, as practiced at 37signals (Basecamp, HEY, Fizzy). Contains 56 rules across 8 categories, prioritized by architectural impact. Derived from official 37signals sources: the Fizzy codebase, STYLE.md, AGENTS.md, the Rails Doctrine, DHH's "On Writing Software Well" series, and the unofficial 37signals style guide (265 Fizzy PRs).

When to Apply

Reference these guidelines when:

• Writing new Rails controllers, models, or views
• Deciding between gems and vanilla Rails
• Modeling state and database schema
• Setting up background jobs, caching, or real-time features
• Reviewing code for 37signals-style conventions
• Refactoring toward rich domain models
• Choosing authentication or authorization approach
• Adding Stimulus controllers or Turbo patterns

Rule Categories by Priority