diff --git a/pkg.go b/pkg.go
index 63ad339..cf46dd3 100644
--- a/pkg.go
+++ b/pkg.go
@@ -10,9 +10,16 @@ import (
 type Error struct {
 	Wrapped error
 	ErrStr  string // wrapped error isn't necessarily json encodable
+	Code    string `json:",omitempty"`
 	File    string
 	Line    int
-	Data    interface{} `json:",omitempty"`
+	Data    any `json:",omitempty"`
+}
+
+type CodableError interface {
+	error
+	WithCode(string) CodableError
+	WithData(any) CodableError
 }
 
 type LogCallback func(Error)
@@ -43,15 +50,20 @@ func callback(wrapped Error) {
 
 // Error implements the error inteface and adds filename and line to the error.
 func (wrapped Error) Error() string {
+	var code string
+	if wrapped.Code != "" {
+		code = wrapped.Code + " "
+	}
 	return fmt.Sprintf(
-		"[%s:%d] %s",
+		"%s[%s:%d] %s",
+		code,
 		wrapped.File,
 		wrapped.Line,
 		wrapped.Wrapped.Error(),
 	)
 }
 
-func create(err error, data interface{}) error {
+func create(err error, data interface{}) *Error {
 	if err == nil {
 		return nil
 	}
@@ -67,27 +79,38 @@ func create(err error, data interface{}) error {
 	}
 
 	callback(wrapped)
-	return wrapped
+	return &wrapped
 }
 
 // Wrap wraps an existing error with file and line.
-func Wrap(err error) error {
+func Wrap(err error) *Error {
 	return create(err, nil)
 }
 
-func WrapData(err error, data interface{}) error {
+func WrapData(err error, data interface{}) *Error {
 	return create(err, data)
 }
 
 // New creates a new wrapped error with file and line.
-func New(msg string, params ...any) error {
+func New(msg string, params ...any) *Error {
 	err := fmt.Errorf(msg, params...)
-	wrapped := create(err, "")
+	wrapped := create(err, nil)
 	return wrapped
 }
 
-func NewData(msg string, data interface{}, params ...any) error {
+// NewData creates a new WrappedError with associated data.
+func NewData(msg string, data interface{}, params ...any) *Error {
 	err := fmt.Errorf(msg, params...)
 	wrapped := create(err, data)
 	return wrapped
 }
+
+func (e *Error) WithCode(code string) CodableError {
+	e.Code = code
+	return e
+}
+
+func (e *Error) WithData(data any) CodableError {
+	e.Data = data
+	return e
+}