Tools: JSON to Go Struct: The Complete Conversion Guide for 2026

Basic Struct Generation ## JSON Tags Explained ## Nested Structs and Arrays ## Nullable and Optional Fields ## Decoding JSON ## Encoding JSON ## Dynamic JSON with map[string]interface{} ## Custom Marshaling ## Tools: json-to-go and quicktype ## Common Pitfalls Converting JSON to Go structs is a daily task for Go backend developers. Here's everything you need to know. For automatic struct generation from JSON: DevToolBox JSON to Go converter — paste JSON, get Go struct instantly Convert JSON to Go structs instantly with DevToolBox's free JSON to Go tool — handles nested objects, arrays, nullable fields, and Go naming conventions. Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to ? It will become hidden in your post, but will still be visible via the comment's permalink. as well , this person and/or CODE_BLOCK: { "id": 1, "name": "Alice", "email": "[email protected]", "active": true } CODE_BLOCK: { "id": 1, "name": "Alice", "email": "[email protected]", "active": true } CODE_BLOCK: { "id": 1, "name": "Alice", "email": "[email protected]", "active": true } CODE_BLOCK: type User struct { ID int `json:"id"` Name string `json:"name"` Email string `json:"email"` Active bool `json:"active"` } CODE_BLOCK: type User struct { ID int `json:"id"` Name string `json:"name"` Email string `json:"email"` Active bool `json:"active"` } CODE_BLOCK: type User struct { ID int `json:"id"` Name string `json:"name"` Email string `json:"email"` Active bool `json:"active"` } CODE_BLOCK: type Product struct { // "json" tag maps field to JSON key ProductID int `json:"product_id"` // omitempty: skip field if zero value Description string `json:"description,omitempty"` // "-": always skip this field Internal string `json:"-"` // string: marshal number as JSON string Price float64 `json:"price,string"` } CODE_BLOCK: type Product struct { // "json" tag maps field to JSON key ProductID int `json:"product_id"` // omitempty: skip field if zero value Description string `json:"description,omitempty"` // "-": always skip this field Internal string `json:"-"` // string: marshal number as JSON string Price float64 `json:"price,string"` } CODE_BLOCK: type Product struct { // "json" tag maps field to JSON key ProductID int `json:"product_id"` // omitempty: skip field if zero value Description string `json:"description,omitempty"` // "-": always skip this field Internal string `json:"-"` // string: marshal number as JSON string Price float64 `json:"price,string"` } CODE_BLOCK: type Order struct { OrderID string `json:"order_id"` Customer Customer `json:"customer"` // nested struct Items []Item `json:"items"` // array of structs Tags []string `json:"tags"` // array of primitives Meta map[string]interface{} `json:"meta"` // dynamic object } type Customer struct { Name string `json:"name"` Email string `json:"email"` Address Address `json:"address"` } type Address struct { Street string `json:"street"` City string `json:"city"` Zip string `json:"zip"` } CODE_BLOCK: type Order struct { OrderID string `json:"order_id"` Customer Customer `json:"customer"` // nested struct Items []Item `json:"items"` // array of structs Tags []string `json:"tags"` // array of primitives Meta map[string]interface{} `json:"meta"` // dynamic object } type Customer struct { Name string `json:"name"` Email string `json:"email"` Address Address `json:"address"` } type Address struct { Street string `json:"street"` City string `json:"city"` Zip string `json:"zip"` } CODE_BLOCK: type Order struct { OrderID string `json:"order_id"` Customer Customer `json:"customer"` // nested struct Items []Item `json:"items"` // array of structs Tags []string `json:"tags"` // array of primitives Meta map[string]interface{} `json:"meta"` // dynamic object } type Customer struct { Name string `json:"name"` Email string `json:"email"` Address Address `json:"address"` } type Address struct { Street string `json:"street"` City string `json:"city"` Zip string `json:"zip"` } CODE_BLOCK: // Use pointers for nullable/optional fields type User struct { ID int `json:"id"` Name string `json:"name"` Bio *string `json:"bio"` // null or string AvatarURL *string `json:"avatar_url,omitempty"` // may be absent } // Decoding var user User json.Unmarshal(data, &user) if user.Bio != nil { fmt.Println("Bio:", *user.Bio) } CODE_BLOCK: // Use pointers for nullable/optional fields type User struct { ID int `json:"id"` Name string `json:"name"` Bio *string `json:"bio"` // null or string AvatarURL *string `json:"avatar_url,omitempty"` // may be absent } // Decoding var user User json.Unmarshal(data, &user) if user.Bio != nil { fmt.Println("Bio:", *user.Bio) } CODE_BLOCK: // Use pointers for nullable/optional fields type User struct { ID int `json:"id"` Name string `json:"name"` Bio *string `json:"bio"` // null or string AvatarURL *string `json:"avatar_url,omitempty"` // may be absent } // Decoding var user User json.Unmarshal(data, &user) if user.Bio != nil { fmt.Println("Bio:", *user.Bio) } CODE_BLOCK: import ( "encoding/json" "net/http" ) // From bytes var user User if err := json.Unmarshal(data, &user); err != nil { return fmt.Errorf("parse user: %w", err) } // From HTTP response resp, err := http.Get("https://api.example.com/users/1") if err != nil { /* handle */ } defer resp.Body.Close() var user User if err := json.NewDecoder(resp.Body).Decode(&user); err != nil { return fmt.Errorf("decode user: %w", err) } CODE_BLOCK: import ( "encoding/json" "net/http" ) // From bytes var user User if err := json.Unmarshal(data, &user); err != nil { return fmt.Errorf("parse user: %w", err) } // From HTTP response resp, err := http.Get("https://api.example.com/users/1") if err != nil { /* handle */ } defer resp.Body.Close() var user User if err := json.NewDecoder(resp.Body).Decode(&user); err != nil { return fmt.Errorf("decode user: %w", err) } CODE_BLOCK: import ( "encoding/json" "net/http" ) // From bytes var user User if err := json.Unmarshal(data, &user); err != nil { return fmt.Errorf("parse user: %w", err) } // From HTTP response resp, err := http.Get("https://api.example.com/users/1") if err != nil { /* handle */ } defer resp.Body.Close() var user User if err := json.NewDecoder(resp.Body).Decode(&user); err != nil { return fmt.Errorf("decode user: %w", err) } CODE_BLOCK: user := User{ID: 1, Name: "Alice", Email: "[email protected]"} // To bytes data, err := json.Marshal(user) // Pretty print data, err := json.MarshalIndent(user, "", " ") // To writer (e.g., http.ResponseWriter) w.Header().Set("Content-Type", "application/json") json.NewEncoder(w).Encode(user) CODE_BLOCK: user := User{ID: 1, Name: "Alice", Email: "[email protected]"} // To bytes data, err := json.Marshal(user) // Pretty print data, err := json.MarshalIndent(user, "", " ") // To writer (e.g., http.ResponseWriter) w.Header().Set("Content-Type", "application/json") json.NewEncoder(w).Encode(user) CODE_BLOCK: user := User{ID: 1, Name: "Alice", Email: "[email protected]"} // To bytes data, err := json.Marshal(user) // Pretty print data, err := json.MarshalIndent(user, "", " ") // To writer (e.g., http.ResponseWriter) w.Header().Set("Content-Type", "application/json") json.NewEncoder(w).Encode(user) CODE_BLOCK: // When structure is unknown var result map[string]interface{} json.Unmarshal(data, &result) // Type assertions needed for nested access if name, ok := result["name"].(string); ok { fmt.Println(name) } // Better: json.RawMessage for delayed decoding type Response struct { Status string `json:"status"` Data json.RawMessage `json:"data"` // decode later based on status } CODE_BLOCK: // When structure is unknown var result map[string]interface{} json.Unmarshal(data, &result) // Type assertions needed for nested access if name, ok := result["name"].(string); ok { fmt.Println(name) } // Better: json.RawMessage for delayed decoding type Response struct { Status string `json:"status"` Data json.RawMessage `json:"data"` // decode later based on status } CODE_BLOCK: // When structure is unknown var result map[string]interface{} json.Unmarshal(data, &result) // Type assertions needed for nested access if name, ok := result["name"].(string); ok { fmt.Println(name) } // Better: json.RawMessage for delayed decoding type Response struct { Status string `json:"status"` Data json.RawMessage `json:"data"` // decode later based on status } CODE_BLOCK: // Custom time format type Event struct { Name string `json:"name"` CreatedAt time.Time `json:"created_at"` } // time.Time marshals to RFC3339 by default: "2026-02-27T10:00:00Z" // Custom format: implement json.Marshaler type CustomDate struct { time.Time } func (d CustomDate) MarshalJSON() ([]byte, error) { return json.Marshal(d.Format("2006-01-02")) } func (d *CustomDate) UnmarshalJSON(data []byte) error { var s string if err := json.Unmarshal(data, &s); err != nil { return err } t, err := time.Parse("2006-01-02", s) d.Time = t return err } CODE_BLOCK: // Custom time format type Event struct { Name string `json:"name"` CreatedAt time.Time `json:"created_at"` } // time.Time marshals to RFC3339 by default: "2026-02-27T10:00:00Z" // Custom format: implement json.Marshaler type CustomDate struct { time.Time } func (d CustomDate) MarshalJSON() ([]byte, error) { return json.Marshal(d.Format("2006-01-02")) } func (d *CustomDate) UnmarshalJSON(data []byte) error { var s string if err := json.Unmarshal(data, &s); err != nil { return err } t, err := time.Parse("2006-01-02", s) d.Time = t return err } CODE_BLOCK: // Custom time format type Event struct { Name string `json:"name"` CreatedAt time.Time `json:"created_at"` } // time.Time marshals to RFC3339 by default: "2026-02-27T10:00:00Z" // Custom format: implement json.Marshaler type CustomDate struct { time.Time } func (d CustomDate) MarshalJSON() ([]byte, error) { return json.Marshal(d.Format("2006-01-02")) } func (d *CustomDate) UnmarshalJSON(data []byte) error { var s string if err := json.Unmarshal(data, &s); err != nil { return err } t, err := time.Parse("2006-01-02", s) d.Time = t return err } COMMAND_BLOCK: npm install -g quicktype quicktype --lang go --out types.go data.json COMMAND_BLOCK: npm install -g quicktype quicktype --lang go --out types.go data.json COMMAND_BLOCK: npm install -g quicktype quicktype --lang go --out types.go data.json CODE_BLOCK: // To always marshal as [] not null: type User struct { Tags []string `json:"tags"` } user := User{} // Tags is nil data, _ := json.Marshal(user) // {"tags": null} user.Tags = make([]string, 0) // empty slice data, _ = json.Marshal(user) // {"tags": []} CODE_BLOCK: // To always marshal as [] not null: type User struct { Tags []string `json:"tags"` } user := User{} // Tags is nil data, _ := json.Marshal(user) // {"tags": null} user.Tags = make([]string, 0) // empty slice data, _ = json.Marshal(user) // {"tags": []} CODE_BLOCK: // To always marshal as [] not null: type User struct { Tags []string `json:"tags"` } user := User{} // Tags is nil data, _ := json.Marshal(user) // {"tags": null} user.Tags = make([]string, 0) // empty slice data, _ = json.Marshal(user) // {"tags": []} - DevToolBox JSON to Go converter — paste JSON, get Go struct instantly - quicktype CLI: - json-to-go (classic web tool): josefpihrt/json-to-go - Unexported fields are ignored — start struct field names with uppercase - Integers vs floats — JSON numbers decode as float64 in interface{} - Missing omitempty — zero values (0, "", false) get marshaled unless omitempty - Nil vs empty slice — var s []int marshals as null, s := []int{} marshals as []