Migrating to Zod v4

Purpose

Comprehensive guide for migrating existing Zod v3 codebases to v4, covering all breaking changes, migration patterns, and testing strategies.

Migration Overview

Zod v4 introduced major performance improvements and API refinements:

• 100x reduction in TypeScript instantiations
• 14x faster string parsing
• 57% smaller bundle size
• Simplified API surface with consistent patterns

Breaking changes are intentional improvements that require code updates.

Breaking Changes