I’m excited to announce Rubree, a modern regular expression editor for Ruby developers — inspired by Rubular but rebuilt from scratch using Ruby, Rails, and WebAssembly (Wasm).
💡 Why Rubree?
Rubular has long been a beloved tool for Rubyists, but it comes with some limitations:
- Runs on older Ruby 2.5.9, which affects speed and maintainability
- Not open-source, making customization and internal investigation difficult
- Matching is server-dependent, requiring backend processing for every input
- Cannot visualize regex structure as a railroad diagram (like Regexper)
- Replacement preview is unavailable
Rubree addresses these challenges by redesigning both the UI and backend logic, running entirely in the browser for a fast, modern regex experience.
🔍 Key Features
■ In-Browser Regex Evaluation (Wasm)
All regex evaluation runs locally in the browser using WebAssembly-powered Ruby.
No network latency, and input responses feel instant.
■ Regex Structure Visualization (Railroad Diagrams)
Using regexp_parser for parsing and railroad_diagrams for SVG rendering,
Rubree provides clear, visual insights into your regex structure.
Perfect when you want to understand how your regex actually connects patterns.
■ Substitution Preview
Replacements directly in the browser and preview results instantly.
■ Ruby Code Snippet Generation
Generate ready-to-use Ruby code directly from your regex input.
■ Shareable URLs
Click the share icon to encode your current input in Base64 and generate a URL.
Share with teammates or in chat, and they can reproduce the same state instantly.
🔧 How to Use
First Visit
- Visit Rubree Demo
- Click "Get started"
- Initial Wasm loading takes about 10 seconds
Subsequent Visits
- Depending on browser cache, a few seconds of loading may occur. This is due to browser behavior, not Wasm.
Basic Flow
- Enter your regex
- Enter sample text
- Check matches, replacement results, and structure diagrams
Try Sample Texts
- Try this example: auto-fill a sample
- Dice icon: display a random text
- Regex Examples: choose from a curated list
Zoom & Share Diagrams
- Magnifying glass icon: zoom in
- Clipboard icon: copy the SVG diagram
🧱 Tech Stack
Rubree is built on Ruby 3.3 + Rails 8.0 and runs in the browser using Wasmify Rails.
Unsupported Versions
-
Ruby 3.4: WebAssembly Ruby has
bigdecimalissues -
Rails 8.1:
jsongem native extensions cannot build on Wasm
Server-side deployment avoids these issues.
⚙️ Backend
- Ruby 3.3
- Rails 8.0
- Regexp::Parser
🎨 Frontend
- Hotwire
- TailwindCSS
- RailroadDiagrams (SVG)
🛠 Development
- Foreman
- Lefthook
🧹 Lint / Testing
- Rubocop / ERB Lint / Biome
- RSpec
- Playwright
- Octocov
🚀 Build / Deployment
- Wasmify Rails → WebAssembly
- GitHub Pages
🤖 Security (Shift-left)
- Dependabot
- Gitleaks
- Brakeman
▶️ CI/CD
- GitHub Actions
🧩 Background
- Started in 2022 as a FJORD BOOT CAMP graduation project
- Inspired by demand for an open-source Rubular alternative
- RubyKaigi 2025 LT helped define the combination of
regexp_parser+railroad_diagrams - Built a browser workflow: AST parsing → SVG rendering → Wasm execution
- Achieved full Rails app execution in the browser
🚀 Final Thoughts
Rubree is a one-stop regex tool for Rubyists, long-time Rubular users, and anyone learning regular expressions.
Use it for quick code testing, learning, or exploring complex regex patterns.
Questions or feature requests? Open an issue on GitHub:
👉 Rubree Issues
Happy regexing! 🔍✨
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