How to Iterate Over String in Go: Simple Guide

In Go, you can iterate over a string using a for loop with range, which gives you the index and the Unicode character (rune) at that position. This method handles multi-byte characters correctly, unlike iterating by byte index.

Syntax

Use a for loop with range to iterate over a string. It returns the index and the rune (Unicode code point) at that position.

• index: position of the character in bytes
• char: the Unicode character (rune)

go

for index, char := range str {
    // use index and char
}

Example

This example shows how to print each character and its byte index from a string containing English and emoji characters.

go

package main

import "fmt"

func main() {
    str := "Go 🐹!"
    for index, char := range str {
        fmt.Printf("Index: %d, Character: %c\n", index, char)
    }
}

Output

Index: 0, Character: G
Index: 1, Character: o
Index: 2, Character:  
Index: 3, Character: 🐹
Index: 7, Character: !

Common Pitfalls

Iterating over a string by byte index (using for i := 0; i < len(str); i++) can break multi-byte characters like emojis or accented letters. This causes incorrect characters or errors.

Always use range to get full characters (runes) safely.

go

package main

import "fmt"

func main() {
    str := "Go 🐹!"
    fmt.Println("Wrong way (by byte):")
    for i := 0; i < len(str); i++ {
        fmt.Printf("%c ", str[i])
    }
    fmt.Println("\nRight way (by rune):")
    for _, char := range str {
        fmt.Printf("%c ", char)
    }
}

Output

Wrong way (by byte):
G o   ï  
Right way (by rune):
G o   🐹 ! 

Quick Reference

• Use for index, char := range str to iterate characters safely.
• Index is byte position, char is rune (Unicode character).
• Do not iterate by byte index for strings with multi-byte characters.

Key Takeaways

Use for-range loop to iterate over string characters safely in Go.

Range returns byte index and Unicode character (rune) for each iteration.

Avoid iterating by byte index to prevent breaking multi-byte characters.

The index from range is byte position, not character count.

This method works correctly with emojis and accented letters.