String#empty?

str.empty? -> true or false

Returns: boolean · Updated March 13, 2026 · String Methods

strings checking boolean

The empty? method checks whether a string contains any characters. It returns true if the string’s length is zero, and false otherwise.

Syntax

string.empty?

Parameters

This method takes no parameters.

Examples

Basic usage

"".empty?
# => true

"hello".empty?
# => false

Checking before operations

def greet(name)
  name = name.strip
  if name.empty?
    "Hello, stranger!"
  else
    "Hello, #{name}!"
  end
end

greet("   ")
# => "Hello, stranger!"

greet("Ada")
# => "Hello, Ada!"

Common Patterns

Form validation

def validate_form(name:, email:)
  errors = []
  
  if name.strip.empty?
    errors << "Name is required"
  end
  
  if email.strip.empty?
    errors << "Email is required"
  end
  
  errors
end

validate_form(name: "  ", email: "ada@ruby.org")
# => ["Name is required"]

Conditional rendering

def render_sidebar(content)
  if content.nil? || content.empty?
    "<aside class=\"empty\">No content</aside>"
  else
    "<aside>#{content}</aside>"
  end
end

Array filtering

strings = ["ruby", "", "rails", "   ", "hanami"]

strings.reject(&:empty?)
# => ["ruby", "rails", "   "]

strings.reject { |s| s.strip.empty? }
# => ["ruby", "rails", "hanami"]

Empty String vs Nil

Ruby distinguishes between empty string and nil:

"".nil?     # => false
"".empty?  # => true

nil.nil?    # => true
nil.empty?  # => NoMethodError (undefined method for nil)

# Use safe navigation operator with nil
nil&.empty? # => nil (returns nil instead of raising error)

The safe navigation operator (&.) is particularly useful when you’re unsure whether the variable might be nil.

Performance

The empty? method runs in O(1) constant time because Ruby stores string length as metadata. This is more efficient than comparing str.length == 0, though the difference is negligible for single checks.

Edge Cases

# Whitespace is not empty
" ".empty?      # => false
"\n".empty?     # => false
"\t".empty?     # => false

# Use strip to handle whitespace
" ".strip.empty? # => true