Zod Schema Generator Comparison

Comprehensive comparison of Orval, openapi-ts, Skmtc, and Kubb for generating Zod schemas from OpenAPI specifications.

Test Schema: GitHub REST API v3 OpenAPI spec (11.1MB JSON)

Performance & Output (Zod Only)

Metric	Kubb	openapi-ts	Orval	Skmtc	Winner
Average Generation Time	8.7s	11.8s	5.0s	2.4s	🏆 Skmtc (fastest)
Output File Size (Zod)	3.4MB	2.6MB	4.5MB	1.2MB	🏆 Skmtc (smallest)
Total Output Size	3.6MB	2.6MB	4.5MB	1.2MB	🏆 Skmtc (smallest)
Number of Files	2 files	1 file	1 file	1 file	openapi-ts/Orval/Skmtc
Output Path	`src/gen/zod.ts`	`src/client/zod.gen.ts`	`src/gen/github-zod.ts`	`skmtc-zod-output/types.generated.ts`	-

Configuration

Feature	Kubb	openapi-ts	Orval	Skmtc
Config File	`kubb.config.ts`	`openapi-ts.config.ts`	`orval.config.mjs`	`.skmtc/<project>/deno.json`
Package Name	`@kubb/cli` + plugins	`@hey-api/openapi-ts`	`orval`	`skmtc`
Version Tested	4.4.0	0.86.8	8.0.0-rc.0	Latest (Deno)
Config Type	TypeScript	TypeScript	JavaScript/ESM	JSON
Installation	`pnpm add -D @kubb/cli @kubb/core @kubb/plugin-oas @kubb/plugin-zod`	`pnpm add -D -E @hey-api/openapi-ts`	`pnpm add -D orval`	`deno install -A jsr:@skmtc/cli`
Runtime	Node.js	Node.js	Node.js	Deno
Zod Dependency	`pnpm add zod`	`pnpm add zod`	`pnpm add zod`	Included (Deno)

Generated Code Style

Feature	Kubb	openapi-ts	Orval	Skmtc
Zod Import	`import { z } from 'zod/v4'`	`import { z } from 'zod'`	`import * as zod from 'zod'`	`import { z } from 'zod'`
Namespace	Uses `z.object()`	Uses `z.object()`	Uses `zod.object()`	Uses `z.object()`
Property Quotes	Quoted (`"id"`)	Unquoted (`id:`)	Quoted (`"id"`)	Unquoted (`id:`)
Optional Syntax	`z.optional(z.number())`	`z.optional(z.number())`	`zod.number().optional()`	`z.number().optional()`
Formatting	Multi-line, readable	Multi-line, readable	Multi-line, readable	Single-line, compact
TypeScript Integration	❌ No	❌ No	❌ No	❌ No
File Organization	Single file or separate files	Single file	Single file	Single file or separate files

Example Output Comparison

Orval:

export const updatePetBody = zod.object({
  "id": zod.number().optional(),
  "name": zod.string(),
  "photoUrls": zod.array(zod.string()),
  "status": zod.enum(['available', 'pending', 'sold']).optional()
})

openapi-ts:

export const zRoot = z.object({
    current_user_url: z.string(),
    authorizations_url: z.string(),
    hub_url: z.optional(z.string()),
});

export const zSecurityAdvisoryEcosystems = z.enum([
    'rubygems',
    'npm',
    'pip',
]);

Skmtc:

export const root = z.object({current_user_url: z.string(), current_user_authorizations_html_url: z.string(), authorizations_url: z.string(), code_search_url: z.string(), commit_search_url: z.string(), emails_url: z.string(), emojis_url: z.string(), events_url: z.string(), feeds_url: z.string(), followers_url: z.string(), following_url: z.string(), gists_url: z.string(), hub_url: z.string().optional(), issue_search_url: z.string(), issues_url: z.string(), keys_url: z.string(), label_search_url: z.string(), notifications_url: z.string(), organization_url: z.string(), organization_repositories_url: z.string(), organization_teams_url: z.string(), public_gists_url: z.string(), rate_limit_url: z.string(), repository_url: z.string(), repository_search_url: z.string(), current_user_repositories_url: z.string(), starred_url: z.string(), starred_gists_url: z.string(), topic_search_url: z.string().optional(), user_url: z.string(), user_organizations_url: z.string(), user_repositories_url: z.string(), user_search_url: z.string()});

export const securityAdvisoryEcosystems = z.enum(["rubygems", "npm", "pip", "maven", "nuget", "composer", "go", "rust", "erlang", "actions", "pub", "other", "swift"]);

Kubb:

// File: src/gen/zod/rootSchema.ts
import { z } from "zod/v4";

export const rootSchema = z.object({
    "current_user_url": z.string(),
    "current_user_authorizations_html_url": z.string(),
    "authorizations_url": z.string(),
    "code_search_url": z.string(),
    // ... more properties
    "hub_url": z.optional(z.string()),
    // ... more properties
})

Features & Capabilities

Feature	Kubb	openapi-ts	Orval	Skmtc
Zod Schema Generation	✅ Yes	✅ Yes	✅ Yes	✅ Yes
TypeScript Types	❌ No (Zod only mode)	✅ Yes (optional)	❌ No (Zod only mode)	❌ No
SDK Generation	❌ No	✅ Yes (optional)	❌ No	❌ No
Client Generation	❌ No	✅ Yes (optional)	❌ No	❌ No
Request Validation	✅ Yes	✅ Yes	✅ Yes	✅ Yes
Response Validation	✅ Yes	✅ Yes	✅ Yes	✅ Yes
Definitions/Components	✅ Yes	✅ Yes	✅ Yes	✅ Yes
Split Mode	✅ Yes (separate files per schema)	❌ No	✅ Yes (tags-split, split)	✅ Yes (separate files per schema)
Single File Mode	✅ Yes	✅ Yes	✅ Yes	✅ Yes
Compact Output	❌ No	❌ No	❌ No	✅ Yes (single-line)
Type Integration	❌ No	❌ No	❌ No	❌ No

Timing Details

Tool	Run 1	Run 2	Run 3	Average
Kubb	8.661s	8.499s	8.909s	8.7s
openapi-ts	11.706s	11.672s	12.093s	11.8s
Orval	5.135s	4.827s	5.138s	5.0s
Skmtc	2.371s	2.361s	2.331s	2.4s

Configuration Examples

Orval Configuration

File: orval.config.mjs

import { defineConfig } from 'orval';

export default defineConfig({
  github: {
    input: {
      target: './schemas/github-openapi.json',
    },
    output: {
      client: 'zod',
      mode: 'single',
      target: './src/gen/github-zod.ts',
    },
  },
});

openapi-ts Configuration

File: openapi-ts.config.ts

import { defineConfig } from '@hey-api/openapi-ts';

export default defineConfig({
  input: './schemas/github-openapi.json',
  output: 'src/client',
  plugins: [
    {
      name: 'zod',
      requests: true,
      responses: true,
      definitions: true,
    },
  ],
});

Skmtc Configuration

File: .skmtc/skmtc-zod/deno.json

{
  "imports": {
    "@skmtc/gen-zod": "jsr:@skmtc/gen-zod@^0.1.0"
  }
}

Command:

skmtc generate skmtc-zod .skmtc/skmtc-zod/openapi.json

Kubb Configuration

File: kubb.config.ts

import { defineConfig } from '@kubb/core'
import { pluginOas } from '@kubb/plugin-oas'
import { pluginZod } from '@kubb/plugin-zod'

export default defineConfig({
  root: '.',
  input: {
    path: './schemas/github-openapi.json',
  },
  output: {
    path: './src/gen',
  },
  plugins: [
    pluginOas({
      output: false, // Disable JSON schema output
    }),
    pluginZod({
      output: {
        path: 'zod.ts', // Single file output
      },
      typed: false,
      dateType: 'stringOffset',
      unknownType: 'unknown',
      version: '4',
    }),
  ],
})

Command:

pnpm generate

Use Case Recommendations

Use Case	Recommended Tool	Reason
Fastest generation	🏆 Skmtc	2.4s - Fastest by far (52% faster than Orval)
Smallest bundle size	🏆 Skmtc	1.2MB - Most compact output (54% smaller than openapi-ts)
Large monorepos	🏆 Kubb or Skmtc	Separate files per schema for better organization
Future extensibility	🏆 openapi-ts	Can add SDK, types, and client later
Deno projects	🏆 Skmtc	Native Deno support
Tree-shakeable imports	🏆 Kubb or Skmtc	Individual files enable optimal tree-shaking (when using split mode)
Simple single-file output	🏆 Skmtc or openapi-ts	Cleanest single-file output (Skmtc: 1.2MB, openapi-ts: 2.6MB)
Plugin-based extensibility	🏆 Kubb	Modular plugin architecture for custom generators

Final Verdict

Choose Skmtc if:

🚀 Speed is the top priority (2.4s - fastest by far, 52% faster than Orval)
📦 Smallest possible bundle size (1.2MB - 54% smaller than openapi-ts)
🦕 You're using Deno or want Deno support
✨ You prefer compact, minified-style output
🎯 Best all-around performance (fastest AND smallest)
📁 Flexibility: supports both single-file and multi-file modes

Choose Orval if:

🎯 Simple single-file output is preferred (4.5MB)
📁 You need tag-based split mode for organization
🔧 You prefer JavaScript/ESM configuration
⚡ Fast generation with readable output (5.0s - second fastest)
🛠️ Node.js ecosystem with excellent npm/pnpm integration

Choose openapi-ts if:

🛠️ Future extensibility is important (SDK, types, client)
📝 You prefer TypeScript configuration
🔄 You might need SDK generation later
📦 Moderate bundle size is acceptable

Choose Kubb if:

🔧 You prefer plugin-based architecture for extensibility
🎯 You need flexible output modes (single file or split mode)
🌳 Tree-shaking is important (supports separate file per schema)
📦 Moderate file size is acceptable (3.4MB - larger than openapi-ts)
⚡ Generation time is acceptable (8.7s - third fastest)

Additional Notes

Skmtc Strengths

Speed: Fastest generation time (2.4s - 52% faster than Orval, 80% faster than openapi-ts)
Size: Smallest output (1.2MB - 54% smaller than openapi-ts, 73% smaller than Orval)
Flexibility: Supports both single-file (1.2MB) and multi-file (870 files) modes
Deno-native: Built for Deno runtime with native TypeScript support
Compact format: Uses single-line compact format for minimal file size
Simplicity: Zero configuration needed for basic usage
Best overall: Only tool that is BOTH fastest AND smallest

Orval Strengths

Speed: Second fastest (5.0s)
Simple output: Single-file output (4.5MB) for easy integration
Flexibility: Multiple output modes (single, split, tags-split)
Organization: Tag-based split mode for large monorepos
Validation options: Can disable validation for broken schemas
Node.js ecosystem: Excellent npm/pnpm integration

openapi-ts Strengths

Extensibility: Can enable additional features (SDK, types) when needed
Modern tooling: TypeScript-first configuration
Complete solution: Types + Schemas + SDK in one tool
Moderate size: 2.6MB output balances size and features

Kubb Strengths

Speed: Third fastest (8.7s)
Flexibility: Supports both single-file (3.4MB) and multi-file modes
Plugin Architecture: Modular, extensible plugin system
Configuration: Highly configurable with transformers and custom generators
Output modes: Can disable JSON schema output for cleaner builds
Barrel files: Automatic index.ts generation for convenient imports

All Tools Excel At

✅ Generating high-quality Zod v4 schemas
✅ Handling large OpenAPI specifications (11MB+ JSON)
✅ Request/response/component schema generation
✅ Easy integration into existing projects
✅ Active development and community support

Key Trade-offs

Speed vs Features:

Skmtc is fastest (2.4s) with flexible single/multi-file modes
Orval is second fastest (5.0s) with more flexibility options
Kubb is third fastest (8.7s) with plugin-based architecture
openapi-ts is slowest (11.8s) but offers SDK/client generation

Size vs Organization:

Skmtc has smallest output (1.2MB single file) - best for bundle size
openapi-ts has second smallest (2.6MB single file)
Kubb has moderate output (3.4MB single file, 3.6MB total)
Orval has larger output (4.5MB single file)

File Organization:

Single-file: Skmtc (1.2MB), openapi-ts (2.6MB), Kubb (3.4MB), Orval (4.5MB)
Multi-file: Skmtc (870 files, 4.4MB), Kubb (2014 files, 9.5MB) - better tree-shaking
Both Skmtc and Kubb support both modes with configuration

Speed Comparison:

Skmtc: 2.4s (baseline - fastest)
Orval: 5.0s (2.08x slower than Skmtc)
Kubb: 8.7s (3.63x slower than Skmtc)
openapi-ts: 11.8s (4.92x slower than Skmtc)

Test Date: October 28, 2025 Test Environment: macOS, Node.js v22.16.0, Deno (latest), pnpm v10.15.1

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Zod Schema Generator Comparison

Performance & Output (Zod Only)

Configuration

Generated Code Style

Example Output Comparison

Features & Capabilities

Timing Details

Configuration Examples

Orval Configuration

openapi-ts Configuration

Skmtc Configuration

Kubb Configuration

Use Case Recommendations

Final Verdict

Choose Skmtc if:

Choose Orval if:

Choose openapi-ts if:

Choose Kubb if:

Additional Notes

Skmtc Strengths

Orval Strengths

openapi-ts Strengths

Kubb Strengths

All Tools Excel At

Key Trade-offs

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File metadata and controls

Zod Schema Generator Comparison

Performance & Output (Zod Only)

Configuration

Generated Code Style

Example Output Comparison

Features & Capabilities

Timing Details

Configuration Examples

Orval Configuration

openapi-ts Configuration

Skmtc Configuration

Kubb Configuration

Use Case Recommendations

Final Verdict

Choose Skmtc if:

Choose Orval if:

Choose openapi-ts if:

Choose Kubb if:

Additional Notes

Skmtc Strengths

Orval Strengths

openapi-ts Strengths

Kubb Strengths

All Tools Excel At

Key Trade-offs