Rubree: A Modern Ruby Regex Editor Running Fully in Your Browser

shimokawa — Mon, 24 Nov 2025 11:55:20 +0000

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 started with Ruby 3.3 + Rails 8.0 running stably on Wasm.
After working through several technical challenges specific to Wasm builds, Rubree now runs on Ruby 4.0 + Rails 8.1 as of April 5, 2026.

⚙️ Backend

Ruby 4.0
Rails 8.1
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! 🔍✨

DEV Community: shimokawa