Blueprint HTML2Slim

A Ruby gem providing a command-line tool to convert HTML and ERB files to Slim format.

Online Converter: Try the web-based version at https://railsblueprint.com/html2slim

• Ruby 2.7 - 3.4 (compatible with latest Ruby versions)

Add this line to your application's Gemfile:

gem 'blueprint-html2slim'

And then execute:

bundle install

Or install it yourself as:

gem install blueprint-html2slim

require 'blueprint/html2slim'

# Create a converter instance
converter = Blueprint::Html2Slim::Converter.new

# Convert HTML string
html = '<div class="container"><h1>Hello</h1></div>'
slim = converter.convert(html)
puts slim
# Output: .container
#           h1 Hello

# Convert ERB string
erb = '<%= form_for @user do |f| %>
  <div class="field">
    <%= f.text_field :name %>
  </div>
<% end %>'
slim = converter.convert(erb)
# Output: = form_for @user do |f|
#           .field
#             = f.text_field :name

# With custom indentation (default is 2)
converter = Blueprint::Html2Slim::Converter.new(indent_size: 4)

Convert a single file:

html2slim index.html
# Creates: index.html.slim

Convert with custom output:

html2slim -o custom.slim index.html

Convert multiple files:

html2slim file1.html file2.erb file3.html.erb

Convert and backup original files:

html2slim -b index.html
# Creates: index.html.slim
# Renames: index.html -> index.html.bak

Convert files in a directory recursively:

html2slim -r ./views

Convert to target directory (preserves structure):

html2slim -t dist/ -r src/
# Converts src/views/index.html to dist/views/index.html.slim

Delete source files after conversion:

html2slim -d old_templates/*.erb
# Converts and deletes the original .erb files

Dry run (preview what would be converted):

html2slim -n file.html

• file.html → file.html.slim
• file.html.erb → file.html.slim
• file.erb → file.slim

• -o, --output FILE - Output file path (only for single file conversion)
• -r, --recursive - Process directories recursively
• -n, --dry-run - Show what would be converted without actually converting
• -d, --delete - Delete source files after successful conversion
• -t, --target-dir DIR - Target directory for converted files (preserves directory structure)
• -f, --force - Overwrite existing files without prompting
• -b, --backup - Backup source files with .bak extension
• -i, --indent SIZE - Indentation size in spaces (default: 2)
• -h, --help - Show help message
• -v, --version - Show version

• Converts HTML tags to Slim syntax
• Handles HTML attributes, IDs, and classes
• Preserves ERB tags (<%= %> and <% %>)
• Supports nested elements
• Handles void elements correctly
• Preserves comments
• Smart output file naming
• Optional source file backup