String#capitalize

str.capitalize -> string

Returns string· Updated May 13, 2026· String Methods

stringscaseconversion

String#capitalize returns a new string with the first character converted to uppercase and all remaining characters converted to lowercase. It is useful for formatting names, titles, and other text that should start with a capital letter.

This method does not modify the original string. It always returns a fresh string object.

Syntax

string.capitalize

Parameters

This method takes no parameters.

Examples

Basic usage

"hello".capitalize
# => "Hello"

"world".capitalize
# => "World"

All remaining characters become lowercase

Every character after the first gets forced to lowercase, regardless of its original case:

"HELLO".capitalize
# => "Hello"

"hELLO".capitalize
# => "Hello"

"HeLLo WoRLD".capitalize
# => "Hello world"

Non-alphabetic first character

If the first character is not an ASCII letter, no uppercasing occurs. Only the rest of the string gets lowercased:

"123abcDEF".capitalize
# => "123abcdef"

"!hello".capitalize
# => "!hello"

Empty string

"".capitalize
# => ""

Unicode and case mapping options

Modern Ruby applies Unicode-aware case mapping by default. That means non-ASCII letters can be capitalized correctly when the string encoding supports them.

"étude".capitalize
# => "Étude"

"über".capitalize
# => "Über"

If you specifically want ASCII-only behavior, pass the :ascii option:

"über".capitalize(:ascii)
# => "über"

Use the default behavior for normal text. Reach for :ascii only when you are intentionally processing ASCII-only identifiers, protocol values, or legacy data.

Mutating version

String#capitalize! modifies the string in place instead of returning a new one:

name = "alice"
name.capitalize!
# => "Alice"
name
# => "Alice"

Note that capitalize! returns nil if no change was needed:

str = "Alice"
str.capitalize!
# => nil
str
# => "Alice"

Common Patterns

Formatting user input

A common pattern is to combine capitalize with other string methods:

def format_name(name)
  name.strip.capitalize
end

format_name("  john doe  ")
# => "John doe"

This converts "john doe" to "John doe" — the first letter becomes uppercase and everything else becomes lowercase.