Question 1

What's the difference between SDL and a code-first schema?

Accepted Answer

SDL is the human-readable text form: `type User { id: ID! }`. Code-first builds the schema from your server-language types (TypeScript classes, Python Pydantic, etc.) and emits SDL as output. Schema-first writes SDL by hand and reads it into the server. Trade-offs: schema-first is more readable, code-first stays in sync with your types automatically. This generator produces SDL, you can use it as a schema-first source or as a target for code-first generation.

Question 2

What scalar types does GraphQL have built in?

Accepted Answer

Five: `Int` (32-bit signed), `Float` (double-precision), `String` (UTF-8), `Boolean`, `ID` (serialized as String, but represents a unique identifier, distinct type for tooling). Notably absent: `DateTime`, `Date`, `JSON`, `URL`, `BigInt`. These are custom scalars, declare `scalar DateTime` and provide serialization in the resolver. Most projects add `DateTime`, `JSON`, and maybe `UUID` as the first custom scalars.

Question 3

When should I use an interface vs a union?

Accepted Answer

**Interface**: shared structure, types that have common fields. `type User implements Node`, `type Post implements Node` where Node has an `id` field. Clients can query for `id` on any Node without knowing the concrete type. **Union**: no shared structure, types that can appear in the same place but have nothing in common. `union SearchResult = User | Post | Comment`, clients must use inline fragments (`... on User`) to query fields. Rule: same fields → interface; same slot, different shapes → union.

Question 4

What's an input type and why can't I reuse a regular type?

Accepted Answer

GraphQL distinguishes output types (what a query returns) from input types (what a mutation takes). Reason: output types can have arguments and resolvers (functions); input types are plain data. So `type User { posts: [Post]! }` (output) can't be used as a mutation argument; you need `input UserInput { name: String! }` separately. Convention: suffix input types with `Input` (`UserInput`, `CreatePostInput`).

Question 5

What does the ! mean?

Accepted Answer

Non-null. `String` is nullable, `String!` is non-null. `[String]` is a nullable list of nullable strings; `[String!]!` is a non-null list of non-null strings. The position matters: `[String]!` = non-null list, but elements can be null. The `!` on the inside is about element nullability; the `!` on the outside is about the list itself. Convention: be liberal with `!` on internal types; conservative on external API to leave room for future changes.

Question 6

How do I model relationships?

Accepted Answer

Field references between types. `type Post { author: User! }`, a post has an author. `type User { posts: [Post!]! }`, a user has posts. Pagination uses connection-style fields: `posts(first: Int, after: String): PostConnection` returning `{ edges: [...], pageInfo: {...} }`. The Relay-style cursor pagination is the GraphQL standard; offset-based pagination works too but doesn't handle inserted/deleted items as cleanly.

Question 7

Should I use enums or constants?

Accepted Answer

Enums in GraphQL are first-class types: `enum Role { ADMIN EDITOR VIEWER }`. Clients see the allowed values; servers validate inputs against them; IDE autocomplete works. Use enums for closed sets of values (status codes, roles, categories). Use String for open sets (tags, custom labels). Don't put numbers in enums, GraphQL enums are always uppercase names, no associated values.

Question 8

Is my schema sent anywhere?

Accepted Answer

No. The generator builds SDL strings from form inputs in your browser. The output is yours, paste it into your server, save it to a file, or feed it to code-generation tools (graphql-codegen).

Question 9

What standards does GraphQL Schema Generator validate against?

Accepted Answer

GraphQL Schema Generator checks compliance with Output format specification.

Question 10

What are the limitations of GraphQL Schema Generator?

Accepted Answer

Output is template-based, may need customization Does not validate output against target system

Type Kind	Semantic Context	Standard Usage
Object	Output Channel	Data returned to queries/mutations
Input	Input Channel	Data passed into mutation arguments
Interface	Shared Selection	Common field sets across multiple types
Enum	Closed Set	Restricted string values for flags/roles
Union	Polymorphic Slot	Selection across non-related concrete types

GraphQL Schema Generator

Privacy note

How to Use GraphQL Schema Generator

Describe Your Data

Generate Schema

Copy Schema

GraphQL Schema Generator: the essentials

Key points

Learn More

cURL Cheatsheet for Developers 2026 — Every Flag You Actually Use

Essential API and Web Development Tools for Frontend and Backend Engineers

How to Debug Webhooks: A Complete Developer Playbook (2026)

What is GraphQL Schema Generator?

Frequently Asked Questions

Technical Deep Dive

GraphQL Schema Generator

Built for Devs

Smart Defaults

Workflow-Friendly

01 GQL Type Kind Matrix

02 Schema Construction Pipeline

Runs 100% in your browser

You Might Also Need

Git Commit Message Generator

Regex Explainer

AI Code Review Assistant

API Client Code Generator