Runtime Validation with Zod
Validate and infer API response types with Zod schemas.
Runtime Validation with Zod is a free TypeScript Academy lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the TypeScript Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Welcome
Installing Zod
npm install zodBasic Schema
import { z } from 'zod';
const UserSchema = z.object({
id: z.number(),
name: z.string(),
email: z.string().email(),
});
type User = z.infer<typeof UserSchema>;Parsing Data
const user = UserSchema.parse({ id: 1, name: 'Alice', email: 'a@b.com' });
// user is typed as UserSafe Parsing
const result = UserSchema.safeParse(unknownData);
if (result.success) {
console.log(result.data); // User
} else {
console.log(result.error.issues);
}Array and Object Schemas
const UsersSchema = z.array(UserSchema);
const CreateUserSchema = UserSchema.omit({ id: true });Optional and Nullable
const Schema = z.object({
name: z.string(),
bio: z.string().optional(), // string | undefined
avatar: z.string().nullable(), // string | null
});Enum and Union
const StatusSchema = z.enum(['active', 'inactive', 'banned']);
const InputSchema = z.string().or(z.number());Transform
const PriceSchema = z.string().transform(s => parseFloat(s));Zod in API Routes
app.post('/users', async (req, res) => {
const result = CreateUserSchema.safeParse(req.body);
if (!result.success) return res.status(400).json(result.error);
const user = await db.create(result.data); // typed!
res.json(user);
});Custom Validators
const PasswordSchema = z.string().min(8).refine(
s => /[A-Z]/.test(s), { message: 'Need uppercase' }
);Quick Check
Recap
Frequently asked questions
Is the “Runtime Validation with Zod” lesson free?
Yes — the full text of “Runtime Validation with Zod” is free to read here on the web, and the TypeScript Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the TypeScript Academy course, upgrade to CoddyKit PRO.
What will I learn in “Runtime Validation with Zod”?
Validate and infer API response types with Zod schemas. You practise TypeScript Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start TypeScript Academy?
No prior experience is required. TypeScript Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Runtime Validation with Zod” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this TypeScript Academy lesson?
Yes. Every TypeScript Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.