Using omitempty in Go JSON Struct Tags

The omitempty Tag in Go

The omitempty option tells Go's JSON encoder to skip a field if it holds its zero value. This produces cleaner, smaller JSON output.

Zero Values by Type

Type	Zero Value
string	""
int, float64	0
bool	false
pointer	nil
slice, map	nil (not empty)
struct	never omitted

Example

type User struct {
    Name     string  `json:"name"`
    Email    string  `json:"email,omitempty"`
    Age      int     `json:"age,omitempty"`
    Verified bool    `json:"verified,omitempty"`
    Bio      *string `json:"bio,omitempty"`
}

If Email is "", Age is 0, and Verified is false, marshaling produces:

{ "name": "Alice" }

The Bool and Zero Pitfall

A common mistake: if false or 0 are valid values in your domain (e.g., a boolean flag that can legitimately be false), omitempty will hide them. The solution is to use a pointer type:

Verified *bool `json:"verified,omitempty"`

Now nil means "not provided" and is omitted, while false is a valid value and will be included.

Structs Are Never Omitted

omitempty on a struct field has no effect — an empty struct {} is always included. Use a pointer to the struct if you need omit behavior:

Address *Address `json:"address,omitempty"`

When to Use omitempty

Use it for optional fields in PATCH requests, sparse response objects, and anywhere the absence of a field carries meaning. Avoid it for fields where zero is a valid, meaningful value.