JSON to Go structs
freeGenerate Go struct definitions with json tags and idiomatic field naming.
package main
type Root struct {
Id string `json:"id"`
Name string `json:"name"`
Email string `json:"email"`
Age int64 `json:"age"`
Bio interface{} `json:"bio"`
Address Address `json:"address"`
Tags []string `json:"tags"`
CreatedAt string `json:"createdAt"`
Verified bool `json:"verified"`
}
type Address struct {
Street string `json:"street"`
City string `json:"city"`
Country string `json:"country"`
PostalCode string `json:"postalCode"`
}
Generate Go struct definitions from any JSON sample. The converter handles the small but important Go idioms: PascalCase field names with `json:"..."` tags, pointer-with-omitempty for optional fields, `*T` for nullable values, and consistent type naming across the whole document tree. Pick your package name, tag style (original / snake_case / camelCase), and whether optional fields get `,omitempty`.
Common use cases
- Modelling REST API responses. Drop the JSON payload, copy the structs into a `types.go` file, and use `json.Unmarshal` directly. Optional fields with `,omitempty` round-trip cleanly back to JSON.
- Defining gRPC / Protobuf adjacents. When you need a Go representation that mirrors a JSON shape used elsewhere (config files, webhook payloads, etc.) without owning the canonical schema.
- Webhook handlers. Generate from a sample webhook payload — Stripe, GitHub, Slack — to get a typed handler instead of `map[string]interface{}` access.
- Config file parsing. Strongly type your YAML/JSON config: generate the structs, then `yaml.Unmarshal` or `json.Unmarshal` into them with confidence about which fields are required.
Frequently asked
Why are some fields `*string` instead of `string`?
Pointers are how Go distinguishes 'absent' from 'zero value' in JSON. Optional fields use `*T` so that an absent key stays as nil rather than getting the type's zero value, which would round-trip incorrectly.
What does `,omitempty` do?
When marshalling back to JSON, fields tagged with `,omitempty` are excluded if their value is the zero value (or nil pointer). Turn it off if you always want every field present in the output.
Should I use snake_case or camelCase tags?
Match what your API actually returns. Many REST APIs use snake_case; GraphQL and many newer APIs use camelCase. 'Original' preserves whatever your sample uses, which is usually the safest bet.
Why is my nullable field `interface{}` instead of `*string`?
If a field is observed as both `string` and `null` across the sample, it gets the nullable string treatment (`*string`). If it's observed as multiple non-null types, the inference falls back to `interface{}` since Go has no union types.
Does it support `encoding/json` v2?
The output works with both v1 and v2. v2 adds support for `omitzero` (more precise than `omitempty`) — you can search/replace if you prefer the stricter semantic.
Can I add custom tags (e.g., `bson`, `gorm`)?
Not currently. The output is a starting point — append additional tags by hand to specific fields as needed. A future option may surface this directly.