Define String Constants in Kotlin

Using string constants to represent values that stay the same across the course of your application’s lifecycle is crucial while working on Kotlin projects.

String constants not only improve the readability and maintainability of your code but also aid in reducing typographical errors. In this post, we’ll examine through examples how to define string constants in Kotlin.

To define a String constant in Kotlin, use constant and val keyword for the String.

Why Use String Constants ?

Before we dive into the Kotlin code, let’s understand why it’s a good practice to use string constants:

  1. Readability: Constants have meaningful names, making your code more self-explanatory. Developers reading your code can easily understand the purpose of the value.
  2. Maintainability: If you need to change a constant value, you only need to update it in one place. This avoids the risk of inconsistencies caused by multiple occurrences of the same value.
  3. Error Prevention: Typos are a common source of bugs. Using constants reduces the chances of introducing errors due to misspelled strings.

Defining String Constants in Kotlin

In Kotlin, you can define string constants in several ways, but one of the most common and recommended approaches is to use the const val keyword combination within a companion object. Here’s how you can do it:

In the code above, we’ve created a class called Constants, and within it, a companion object to group our constants.

Each constant is defined using the const val keyword combination. In this example, we’ve defined two string constants: API_BASE_URL and API_KEY.

Using String Constants

Once you’ve defined your string constants, you can easily use them throughout your Kotlin code:

fun main() {
    val apiUrl = Constants.API_BASE_URL
    val apiKey = Constants.API_KEY

    println("Connecting to API at $apiUrl with API key: $apiKey")

In this main function, we access the API_BASE_URL and API_KEY constants from the Constants class. This makes the code more readable and helps prevent errors when referring to these values.


It is recommended that you use string constants in your Kotlin applications to produce code that is easier to read, maintain, and write without mistakes. You may efficiently organise and access your constants across your codebase by defining them inside a companion object. Therefore, to enjoy these advantages the next time you use a constant string in a Kotlin project, keep in mind to specify it correctly.

These recommendations can help you create cleaner, more dependable Kotlin code for your website, resulting in a faster development cycle and a better user experience.

Happy coding!

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