String#downcase

str.downcase -> string

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

strings case conversion unicode

String#downcase returns a new string with all characters converted to lowercase. It is useful for case-insensitive comparisons, normalizing user input, and formatting output for display.

This method does not modify the original string—it always returns a new string.

Syntax

string.downcase

Parameters

This method takes no parameters. It operates on all characters in the string.

Examples

Basic usage

"Hello World".downcase
# => "hello world"

"Ruby Programming".downcase
# => "ruby programming"

With Unicode characters

"ÇÀÂ".downcase
# => "çàâ"

"über".downcase
# => "über"

"Ångström".downcase
# => "ångström"

Working with special characters

"Numbers: 123".downcase
# => "numbers: 123"

"Symbols: !@#".downcase
# => "symbols: !@#"

Common Patterns

Case-insensitive comparison

When comparing strings without regard to case, convert both to lowercase first:

username = "JohnDoe"
username.downcase == "johndoe"
# => true

Normalizing user input

Many applications normalize user input to ensure consistent storage:

def normalize_name(name)
  name.strip.downcase
end

normalize_name("  JOHN ")
# => "john"

normalize_name("ALICE")
# => "alice"

Unicode Support

Ruby handles Unicode properly. The method respects Unicode character properties, so it works correctly with international text. The Turkish dotted and dotless i problem is handled correctly in Ruby 2.5+.