Developer Tools
Generate Go Structs From JSON
JSON To Go Struct for formatting, validating, converting, or cleaning JSON data in the browser.
Direct Answer
Use the JSON To Go Struct tool when you have sample API or config JSON and need a starting Go struct with properly capitalized fields and json tags for unmarshaling.
What the Generated Struct Handles Automatically
Go requires exported fields to be capitalized for the encoding/json package to read or write them, and it needs an explicit tag to map back to the original JSON key name, both of which a generator produces from your sample data.
- Every JSON key becomes a capitalized Go field name so it is exported and visible to encoding/json
- A json struct tag is added to map the Go field back to the exact original JSON key
- Nested JSON objects become nested Go structs, generated as separate named types
- JSON arrays become Go slices of the corresponding element type
What You Still Need to Review Manually
A generated struct is a solid starting point, not a finished type, because a single JSON sample cannot tell the generator everything about which fields are truly optional, nullable, or variable in type.
- Fields that might be missing in other responses need omitempty added to their tag, or a pointer type if you must distinguish missing from zero value
- A field that sometimes holds a string and sometimes a number needs to become an interface type, with manual type assertions afterward
- Date and time strings arrive as plain Go strings and need explicit parsing into a time.Time value, since encoding/json does not infer this
- Very large integer IDs may need to be represented as a string or json.Number to avoid float64 precision loss during unmarshaling
How to Use JSON To Go Struct
- Paste or type your content into the input box.
- The transformed result appears instantly in the result panel below.
- Click Copy result to copy the output to your clipboard.
- Download .txt saves the transformed text as a file.
- Reset clears everything and lets you start over.
Reference
| Feature | Details |
|---|---|
| Purpose | Transform pasted text into a cleaner or different format. |
| Input | Text, lines, lists, or copied content. |
| Result | Transformed text ready to copy or download. |
| Best for | Cleanup, formatting, list preparation, and copy-paste workflows. |
| Category | Developer Tools |
| Works on | Desktop, tablet, and mobile browsers |
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A Focused JSON To Go Struct Alternative
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Useful Related Tools
Frequently Asked Questions
Why are all the fields in my generated Go struct capitalized?
Go's encoding/json package can only marshal and unmarshal exported fields, and in Go a field is exported only if its name starts with an uppercase letter. The generator capitalizes every field name for this reason, then adds a json struct tag to preserve the original lowercase or camelCase key from your JSON.
What does the json struct tag actually do?
The struct tag tells encoding/json which JSON key maps to that Go field during marshaling and unmarshaling, since the Go field name itself had to be capitalized and may no longer match the original JSON key exactly. Without the tag, Go would look for a JSON key matching the capitalized field name, which usually does not exist in real API responses.
Should I add omitempty to every field in my generated struct?
Not automatically. Add omitempty only to fields that are genuinely optional and where you want them excluded from JSON output entirely when they hold a zero value. Be cautious with omitempty on fields where a legitimate zero value, like the number 0 or false, needs to be sent explicitly, since omitempty would incorrectly drop those too.
Why does my generated struct use a pointer type for some fields?
A pointer type lets you distinguish a field that is genuinely missing or null from one that is present but holds the zero value, such as an empty string or 0. If a generator sees a null value in your sample JSON, it typically generates a pointer type for that field so your code can check for nil explicitly.
How do I handle a JSON field that has different types in different responses?
Go is statically typed and a struct field can only have one declared type, so if a field is sometimes a string and sometimes a number across different API responses, you need to type it as an empty interface, then perform a type assertion or type switch in your code after unmarshaling to handle each case.
Why does my date field just show up as a string in the generated struct?
JSON has no native date type, so a date is always transmitted as a plain string, and a generator has no reliable way to know a string like "2024-01-05" should become a Go time value. Keep the field as a string in the struct and parse it explicitly with time.Parse using the correct layout, or implement a custom UnmarshalJSON method if the API always uses a consistent date format.
Why did my large ID number lose precision after unmarshaling into my Go struct?
If the generated field type is float64, Go's default for a JSON number field when using generic parsing, rather than int64 or a string, integers larger than about 9 quadrillion can lose precision because float64 cannot represent every large integer exactly. Use int64 for the field type if the source values are always whole numbers, or a string if you need to safely pass through arbitrarily large numbers like 64-bit database IDs.
Does the generated Go struct need manual review before using it in production code?
Yes. A single JSON sample only shows the generator one possible shape of the data, so fields that happen to be present and non-null in your sample get generated as required, non-pointer types, when in reality the API might omit them or return null in other cases. Review nullable and optional fields carefully, and test with multiple real API responses before finalizing the struct.
Why does my generated struct have a separate type for a nested object instead of an inline definition?
Go does not have a convenient shorthand for deeply inline anonymous nested struct literals in most generator output, so a nested JSON object typically becomes its own named struct type, referenced as a field in the parent struct. This keeps the generated code more readable and reusable if the same nested shape appears in multiple places.
How are JSON arrays of objects converted into Go types?
An array of objects becomes a Go slice of the corresponding struct type, generated from the shape of the objects found in your sample array. If the array is empty in your sample JSON, the generator cannot infer the element's fields and will likely fall back to a generic slice type or placeholder.
What happens if my JSON has a field name that is a Go reserved word, like "type" or "range"?
The generator will typically rename the Go field to something like TypeField, since capitalizing already avoids most keyword conflicts because Go keywords are lowercase, while keeping the original lowercase key in the json struct tag so serialization still matches the source data correctly.
Should I use encoding/json or a third-party library with my generated struct?
The generated struct's json tags work directly with the standard library's encoding/json package, which is sufficient for most use cases. Consider a third-party library only if you have measured a specific performance bottleneck, since most alternatives are largely drop-in compatible with the same tag conventions.
What is the JSON To Go Struct?
The JSON To Go Struct is a free online utility for developer formatting, validation, and debugging tasks. It changes pasted text into the requested format and shows the transformed output ready to copy.