What is the difference between make() and new() in Go?
Jun 19, 2025 am 01:00 AM
In Go, new() is used to allocate and return a zero-value pointer to any type, while make() is used specifically to initialize slices, maps, and channels. The specific differences are as follows: 1.new(T) allocates memory and returns a *T type pointer, suitable for scenarios where pointers to structures or basic types are needed without complex initialization; 2.make() is only used for slice, map and chan types. It not only allocates memory but also performs internal structure settings so that these types can be used directly; 3.new() returns a pointer, make() returns a non-pointer instance of the actual type; 4.new() is suitable for any type, make() is only for specific built-in types. The two have different uses and are not interchangeable.
In Go, make() and new() are both built-in functions used for allocation, but they serve different purposes and are used in different contexts. Understanding when to use each is key to writing effective Go code.
When to Use new()
new(T) is used to allocate memory for a type T and returns a pointer to the zero value of that type. It doesn't initialize the value beyond setting it to its default (like 0 for integers, false for booleans, nil for points).
For example:
p := new(int) fmt.Println(*p) // prints: 0
This creates a pointer to an integer with the initial value of 0. You'll typically use new() when you need a pointer to a struct or a basic type, especially if you want to avoid manually initializing it to zero yourself.
A common case might be:
type User struct {
Name string
Age int
}
u := new(User)
// u is now a pointer to a User with empty Name and Age 0 Just remember, new() gives you a pointer, and it only zeroes out the memory — it doesn't do any custom initialization logic.
When to Use make()
make() is specifically for initializing slices, maps, and channels. These types require more than just allocating memory — they need internal structure setup to be usable.
You can't use make() for arbitrary types; it only works with those three built-in types.
Examples:
s := make([]int, 0, 5) // slice with length 0, capacity 5 m := make(map[string]int) // empty map ready to use c := make(chan int) // unbuffered channel
Using make() ensures these types are properly initialized so you can start appending to slices, putting values ??into maps, or sending data through channels right away.
If you tried to declare them without make() like this:
var m map[string]int m["key"] = 42 // panic: assignment to entry in nil map
You'd get a runtime error because the map wasn't initialized.
Key Differences Summary
-
Purpose :
-
new()allocates memory and zeroes it. -
make()initializes certain types (slice,map,chan) so they're ready for use.
-
-
Return Type :
-
new(T)returns*T. -
make()returns the actual type (T, not*T).
-
-
Usability :
-
new()works with any type. -
make()only works with slices, maps, and channels.
-
So while both help with memory management, they're not interchangeable — make() handles more complex setup for specific types, and new() simply allocates and zeros.
That's basically it. They each have their own role, and once you know what kind of type you're dealing with, choosing between them becomes straightforward.
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