An empty interface is a special type in Go language that can store any type of value, written as interface{} without implementing any method. It is suitable for handling unknown or mutable data types, creating generic-like functions, and storing slices or maps of mixed types. For example, map[string]interface{} is often used to parse JSON data. When using an empty interface, type checking must be performed through type assertions or type switches to ensure runtime safety. However, excessive use of empty interfaces can cause code confusion and difficult to debug, so the generic mechanism introduced in Go 1.18 should be given priority and use empty interfaces when necessary to avoid abuse just to mimic dynamic typing.
In Go, an empty interface is a special type that can hold values ??of any type. It's written as interface{}
and doesn't require any methods to be implemented. This makes it extremely flexible but also comes with trade-offs.

What Exactly Is an Empty Interface?
An empty interface in Go has no method requirements, which means any type automatically satisfyes it. That's why you often see it used when the exact type isn't known ahead of time — like when working with JSON data or building generic functions.

For example:
var myVar interface{} myVar = "hello" myVar = 42 myVar = []int{1, 2, 3}
All of these assignments are valid because interface{}
can take any value.

Common Use Cases
Empty interfaces come in handy in several real-world scenarios:
- Handling unknown or variable data types , such as parsing JSON from external APIs.
- Creating generic-like functions before Go introduced generics in version 1.18.
- Storing mixed-type values ??in slices or maps , like
[]interface{}
ormap[string]interface{}
.
Here's how you might use one:
data := map[string]interface{}{ "name": "Alice", "age": 30, "active": true, }
This pattern is especially common when unmarshaling JSON into a structure that may vary.
Type Assertion and Type Switching
Because interface{}
doesn't know what type it holds at compile time, you need to perform type assertions or type switches to get useful behavior out of it.
Type Assertion
If you're pretty sure what type is stored, you can assert it:
str, ok := myVar.(string) if ok { fmt.Println("It's a string:", str) } else { fmt.Println("Not a string") }
Type Switch
When dealing with multiple possible types, a type switch is cleaner:
switch v := myVar.(type) { case string: fmt.Println("String value:", v) case int: fmt.Println("Integer value:", v) default: fmt.Println("Unknown type") }
These checks are essential because working directly with an empty interface gives you very little compile-time safety.
Caveats and Best Practices
Using empty interfaces too freely can lead to messy, hard-to-debug code. Here are a few tips:
- Avoid overusing
interface{}
unless you really need flexibility. - Prefer using Go's built-in generics (available from 1.18 ) for writing reusable typed functions.
- Always validate and check types before asserting to avoid runtime panics.
- Don't use
interface{}
just to mimic dynamic typing — Go isn't designed for that.
For instance, instead of this:
func PrintValue(v interface{}) { fmt.Println(v) }
You might prefer a generic function:
func PrintValue[T any](v T) { fmt.Println(v) }
Which gives better type safety and clarity.
So while an empty interface gives you flexibility, it should be used carefully and only when necessary. Mostly, it's a tool for handling unknown types dynamically — but not a substitute for proper typing.
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