What is a symbol in Ruby, and when should I use one instead of a string?

A minimal example

A string is a piece of text in quotes. A hash is a collection of key and value pairs, written between braces. Here a hash uses symbols as keys:

person = { name: "Ada", city: "London" }

p person[:name]    # => "Ada"
p person["name"]   # => nil
p person.keys      # => [:name, :city]

The second lookup returns nil because the key is the symbol :name, not the string "name". Ruby treats those as different things, and that one fact causes most symbol confusion.

The Ruby documentation for Symbol puts it this way: Symbol objects represent identifiers inside the interpreter, while String objects represent text or data. An identifier is a name your program uses for something, like a method or a variable.

Why a symbol is different from a string

The same documentation says that the same Symbol object is created for a given name for the whole run of a program. You can see this with equal?, which asks whether two variables point at the very same object:

p :ruby.equal?(:ruby)        # => true
a = "ruby"
b = "ruby"
p a.equal?(b)                # => false
p a == b                     # => true

Two strings with the same letters are equal in value but are two separate objects. Two copies of :ruby are one object. A symbol is also not something you edit. You can add letters to a string with <<, but a symbol has no such method, because it is a label and not a piece of text to change.

You can convert in both directions:

p :name.to_s          # => "name"
p "name".to_sym       # => :name
p "hello world".to_sym  # => :"hello world"

The last line shows that a symbol can hold spaces; Ruby then writes it with quotes after the colon, as the literals page describes.

Which should I use?

Situation	Use	Why
Hash keys you write in your own code	Symbol	Short, and the same object every time
Options and keyword arguments	Symbol	The key: value syntax is the same as for symbol keys in a hash
A status such as :active or :paused	Symbol	A fixed label, not text to show
A name or message a person will read	String	It is text, and you may build or change it
Data that arrives from a form, a file or a web request	String	Outside data is text until you convert it

The syntax documentation for literals shows the hash form { a: 1, b: 2 } and notes that the same syntax is used for keyword arguments in a method call. A keyword argument is a named input you pass like greet(name: "Ada").

Older and newer forms

Code from the guide's era often writes hashes with a hash rocket, as in { :name => "Ada" }. That form still works in Ruby 3.3. The name: "Ada" form is the shorter way to write the same thing. If you want a string key you must keep the rocket: { "name" => "Ada" }.

Mistakes beginners make

1. Looking up the wrong kind of key. A hash built with :name is not found by "name". Check with p hash.keys; if you see colons, use symbols.
2. Using symbols for text. A greeting or a sentence is not a label. If you plan to join it, shout it or print it, make it a string.
3. Converting everything to symbols. If the data came from a user, keep it as a string. Convert only when you need a fixed set of labels.
4. Mixing the two in one hash. { name: "Ada", "age" => 36 } is legal and confusing. Pick one style per hash.

Check this in order

1. Does your lookup return nil when you expected a value? Run p hash.keys.
2. Are the keys printed with a colon, such as :name? Then look them up with a colon.
3. Are the keys in quotes, such as "name"? Then look them up with quotes.
4. Did the data come from outside your program? Convert once, in one place, with to_sym or transform_keys(&:to_sym).

To see what p prints for a symbol versus puts, read What is the difference between puts, print and p in Ruby?, and if you have not set Ruby up yet, start with How do I install Ruby on a Mac with Homebrew and rbenv?. Keep Chapter 3 of the guide open while you try these lines in irb.

Checked on 12 November 2026.