JSON to Go Struct Converter - TestMu AI (Formerly LambdaTest)

What is a JSON to Go Struct Converter?

A JSON to Go struct converter is a code generation tool that reads a JSON document and produces matching Go struct type definitions. It infers a Go type for every value, creates nested structs for nested objects, and attaches json struct tags so the encoding/json package can decode the data and encode it back.

JSON is defined by RFC 8259, and Go reads and writes it through the standard encoding/json package. TestMu AI built this converter for backend developers and QA engineers who turn API payloads into typed Go models for services, CLIs, and test suites.

Working across languages? The same payload converts to TypeScript interfaces with the JSON to TypeScript tool and to Kotlin classes with the JSON to Kotlin tool.

How does this JSON to Go converter work?

The converter parses your JSON with the browser's native JSON parser and walks the result recursively. Each key is capitalized into an exported field, nested objects become named structs, and an array of objects becomes a slice of a generated element type (an orders array produces []Order). Objects with identical field sets are deduplicated into a single struct definition.

Every field carries a json tag with the original key, so the generated code round trips your payload without renaming anything. All processing happens in your browser. Your JSON is never uploaded, stored, or sent to a server.

How to Use the JSON to Golang Converter

• Add your JSON: paste it into the Input box, upload a .txt or .json file, load it from a URL, or click the sample icon to try a demo payload.
• Convert: Auto Update is on by default, so the Go code appears as you type. Uncheck it and click Convert when you prefer manual control.
• Fix invalid input: malformed JSON shows a readable Invalid JSON message instead of output. Run the payload through the JSON Validator to locate the exact syntax error.
• Copy or download: use the copy icon next to the Output box, or download the result as a .go file.

Try this: paste the JSON below and compare your output.

{"name":"Asha","active":true,"orders":[{"id":1,"total":250.75}]}

The converter returns these two structs:

type Root struct {
	Name string `json:"name"`
	Active bool `json:"active"`
	Orders []Order `json:"orders"`
}

type Order struct {
	Id int `json:"id"`
	Total float64 `json:"total"`
}

How to Decode JSON into a Go Struct (json.Unmarshal)

Decoding, also called unmarshaling, turns JSON bytes into a typed Go value. Pass json.Unmarshal a byte slice and a pointer to a variable of the generated struct type.

package main

import (
	"encoding/json"
	"fmt"
)

type Order struct {
	Id    int     `json:"id"`
	Total float64 `json:"total"`
}

type Root struct {
	Name   string  `json:"name"`
	Active bool    `json:"active"`
	Orders []Order `json:"orders"`
}

func main() {
	data := []byte(`{"name":"Asha","active":true,"orders":[{"id":1,"total":250.75}]}`)

	var root Root
	if err := json.Unmarshal(data, &root); err != nil {
		fmt.Println("decode failed:", err)
		return
	}
	fmt.Println(root.Orders[0].Total) // 250.75
}

When the JSON comes from an io.Reader, such as an HTTP response body or a file, wrap the reader with json.NewDecoder and call Decode, for example json.NewDecoder(resp.Body).Decode(&root). If you decode into any instead of a struct, every JSON number arrives as float64, which is one more reason typed structs with int and float64 fields are the safer choice.

How to Encode a Go Struct back to JSON (json.Marshal)

Encoding, also called marshaling, is the reverse trip. json.Marshal returns the JSON encoding of the value you pass in, and json.MarshalIndent formats the same output with indentation for logs and config files.

root := Root{Name: "Asha", Active: true, Orders: []Order{{Id: 1, Total: 250.75}}}

out, err := json.Marshal(root)
if err != nil {
	fmt.Println("encode failed:", err)
	return
}
fmt.Println(string(out))
// {"name":"Asha","active":true,"orders":[{"id":1,"total":250.75}]}

pretty, _ := json.MarshalIndent(root, "", "  ")
fmt.Println(string(pretty))

Only exported fields appear in the result, and the json tags supply the output keys. That is why every struct this converter generates uses capitalized field names with the original JSON key preserved in the tag.

Go Struct Tags and the omitempty Option

A struct tag is the string after a field declaration, and the json key inside it controls how encoding/json treats that field. The first item renames the key, and comma separated options follow it.

type Profile struct {
	Name  string `json:"name"`
	Email string `json:"email,omitempty"`
	Notes string `json:"-"`
}

• json:"name": maps the Name field to the name key in the JSON document.
• omitempty: drops the field from output when the value is empty, defined by the encoding/json documentation as false, 0, a nil pointer, a nil interface value, and any array, slice, map, or string of length zero.
• json:"-": excludes the field from both encoding and decoding.

Marshaling the Profile above with an empty Email field therefore omits the email key entirely. Go 1.24 added a stricter option called omitzero (Go 1.24 release notes), which omits a field when its value is the zero value for its type and respects a custom IsZero() bool method.

Handling Nested Objects, Arrays, and Dynamic JSON

• Nested objects: the converter generates named structs for nested objects, so a deeply nested payload becomes a set of small readable types instead of one giant definition. When two different objects share the same key name, review the generated types and rename them if needed.
• Arrays: the element type is inferred from the first element. Arrays that mix types cannot be represented as a typed slice, so change such fields to []any yourself.
• Unknown or changing shapes: use any, the alias for interface{} added in Go 1.18, or map[string]any when keys vary per record. json.RawMessage keeps a subtree as raw bytes so you can decode it later, once you know its shape.
• null values: encoding/json sets interfaces, maps, pointers, and slices to nil for a JSON null and leaves every other type unchanged. Fields that are sometimes null are best declared as pointers, for example *string.

Use Cases of JSON to Go Struct Converter

• API integration: turn a sample response from a REST or GraphQL endpoint into typed models before you write the client.
• API test automation: generate structs for request and response fixtures, then author and run the matching API checks with Kane AI, TestMu AI's AI-native test agent.
• Backend development: define data models for services that validate, persist, or forward JSON payloads.
• Prototyping: scaffold types for a spike without hand writing long field lists.
• Learning Go: see exactly how JSON keys, arrays, and nesting map to Go types and struct tags.
• Polyglot teams: convert the same payload to C# classes with the JSON to C# tool when your services span languages.

Frequently Asked Questions (FAQs)

What is a JSON struct?

A JSON struct usually refers to a Go struct type that mirrors the shape of a JSON document. Each JSON key maps to an exported Go field with a json struct tag, so the encoding/json package can decode JSON values into typed Go data and encode them back.

How do I create a struct in Go?

Declare a struct with the type keyword, a name, and typed fields, for example: type User struct { Name string }. To generate structs from JSON automatically, paste a sample payload into this converter and copy the produced definitions together with their json tags.

How do I decode JSON in Go?

Call json.Unmarshal with a byte slice and a pointer to your struct: err := json.Unmarshal(data, &user). For JSON arriving from an io.Reader, such as an HTTP response body, use json.NewDecoder(resp.Body).Decode(&user). Both functions come from the standard encoding/json package.

How do I encode a struct to JSON in Golang?

Pass the struct value to json.Marshal, which returns the JSON encoding as a byte slice: out, err := json.Marshal(user). For pretty printed output, call json.MarshalIndent with a prefix and an indent string. Only exported fields, those starting with an uppercase letter, appear in the result.

Are field names converted to Go conventions?

The first letter of every JSON key is capitalized so the generated field is exported and visible to the encoding/json package. Keys should already be valid Go identifiers; the original key is preserved in the json struct tag, so decoding and encoding still match your source JSON exactly.

Can I rename the generated struct?

Yes. The converter names the top level type Root and derives nested struct names from your JSON keys. After copying the output, rename any type in your editor. The json struct tags keep the field to key mapping intact, so renaming types never breaks decoding.

Is my JSON data safe?

Yes. All processing happens in your browser using JavaScript. Your JSON is never uploaded, stored, or sent to a server, which makes the tool safe for API responses that contain credentials, tokens, or customer data you cannot share outside your machine.

Which Go versions does the generated code work with?

Structs generated from standard JSON payloads use plain Go types and json struct tags that work with every supported Go release. Two extras mentioned on this page have version floors: the any alias requires Go 1.18 or later, and the omitzero tag option requires Go 1.24 or later.

Paste your next API payload above and copy the generated Go structs in seconds. When those models feed automated API suites, run them at scale on HyperExecute, TestMu AI's test orchestration cloud, and generate matching Java models with the JSON to POJO converter.