Convert between byte array/slice and string

Basics

When you convert between a string and a byte slice (array), you get a brand new slice that contains the same bytes as the string, and vice versa.

• The conversion doesn’t change the data;
• the only difference is that strings are immutable, while byte slices can be modified.

If you need to manipulate the characters (runes) of a string, you may want to convert the string to a rune slice instead. See Convert between rune array/slice and string.

Convert string to bytes

When you convert a string to a byte slice, you get a new slice that contains the same bytes as the string.

b := []byte("ABC€")
fmt.Println(b) // [65 66 67 226 130 172]

Note that the character € is encoded in UTF-8 using 3 bytes. See the Go rune article for more on UTF-8 encoding of Unicode code points.

Convert bytes to string

When you convert a slice of bytes to a string, you get a new string that contains the same bytes as the slice.

s := string([]byte{65, 66, 67, 226, 130, 172})
fmt.Println(s) // ABC€

Performance

These conversions create a new slice or string, and therefore have time complexity proportional to the number of bytes that are processed.

More efficient alternative

In some cases, you might be able to use a string builder, which can concatenate strings without redundant copying:

Efficient string concatenation [full guide]

Further reading

40+ practical string tips [cheat sheet]

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