# JSON Encoding (Go)

> json.Marshal, json.Unmarshal, struct tags, custom marshaling, streaming, RawMessage

- 20 interview questions
- Mid-Level
- [Interview Questions: Go](https://sharpskill.dev/en/technologies/go/interview-questions.md)

## 1. Which function allows encoding a Go struct into JSON?

**Answer**

json.Marshal encodes a Go struct into JSON bytes. This function reads struct tags to customize serialization (renaming, field omission). For streaming to io.Writer, using json.NewEncoder avoids creating an intermediate buffer in memory.

## 2. Which function allows decoding JSON into a Go struct?

**Answer**

json.Unmarshal decodes JSON bytes into a Go struct. A pointer to the target struct must be passed for data to be correctly written. For streaming from io.Reader, json.NewDecoder is more efficient as it avoids loading all JSON into memory.

## 3. Which JSON struct tag allows renaming a field during serialization?

**Answer**

The json:"custom_name" tag allows renaming a field during JSON serialization. For example, a UserID field can become user_id in JSON. This is useful for respecting naming conventions (snake_case in JSON vs CamelCase in Go).

## 17 more questions available

- Which JSON struct tag completely excludes a field from serialization?
- Which JSON struct tag allows omitting a field if its value is empty?

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