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Go Slice vs Array

Last Updated : May 27, 2025

In Go, both arrays and slices are used to store collections of elements, but they have important differences in behavior and usage. In this chapter, we will learn the differences between them with the help of examples.

What is an Array?

An array is a fixed-size collection of items of the same type. The size of an array is part of its type, and it cannot be changed after declaration.

Example

This example shows how to declare and use an array:

package main
import "fmt"

func main() {
    var numbers [3]int = [3]int{10, 20, 30}
    fmt.Println("Array:", numbers)
}

When executed, this program outputs:

Array: [10 20 30]

What is a Slice?

A slice is a flexible, dynamically-sized view into an array. Unlike arrays, slices can grow and shrink.

Example

This example shows how to create and use a slice:

package main
import "fmt"

func main() {
    fruits := []string{"Apple", "Banana", "Cherry"}
    fmt.Println("Slice:", fruits)
}

When executed, this program outputs:

Slice: [Apple Banana Cherry]

Key Differences Between Slice and Array

This table shows the main difference between an array and a table:

Aspect	Difference
Size	Arrays have a fixed size, while slices are dynamically sized.
Declaration	Arrays include the size in their type; slices do not.
Usage	Slices are used more often due to their flexibility.
Memory	Slices are references to underlying arrays, making them more efficient in many scenarios.

Comparison Example

This example compares an array and a slice:

package main
import "fmt"

func main() {
    arr := [3]int{1, 2, 3}      // Array with fixed size
    slc := []int{4, 5, 6}       // Slice with dynamic size

    fmt.Println("Array:", arr)
    fmt.Println("Slice:", slc)
}

When executed, this program outputs:

Array: [1 2 3]
Slice: [4 5 6]

Modifying Elements

Both arrays and slices allow modifying elements by index, but slices can also be resized or appended.

Example

Here, we modify and append to a slice, but not an array:

package main
import "fmt"

func main() {
    array := [2]string{"Go", "Lang"}
    slice := []string{"Hello"}

    array[1] = "Programming"
    slice = append(slice, "World")

    fmt.Println("Modified Array:", array)
    fmt.Println("Appended Slice:", slice)
}

When executed, this program outputs:

Modified Array: [Go Programming]
Appended Slice: [Hello World]

Exercise

Select the correct option to test your understanding of the differences between slices and arrays in Go.

1. An array in Go has a ___ size. --Select-- fixed dynamic unlimited
2. A slice in Go can be resized using ___. --Select-- append() resize() expand()
3. Which of the following is a valid slice declaration? --Select-- var nums []int var nums [int] var nums int[]

Check Answers