Type coercion in Zod

How it works

1. Use z.coerce instead of z. z.coerce.string() is used in place of z.string(). The code parses a string, a number, a boolean and null and prints each result. [1]
2. Convert to numbers and booleans. z.coerce.number() parses values like "42" and "3.5", and the code prints each value with its typeof. z.coerce.boolean() parses several values, including the string "false", and prints what comes out. [1]

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import * as z from "zod";

const str = z.coerce.string();
for (const v of ["tuna", 42, true, null]) {
  const out = str.parse(v);
  console.log(`coerce.string(${JSON.stringify(v)}) ->`, JSON.stringify(out));
}

const num = z.coerce.number();
for (const v of ["42", "3.5", true]) {
  const out = num.parse(v);
  console.log(`coerce.number(${JSON.stringify(v)}) ->`, out, `(${typeof out})`);
}

const bool = z.coerce.boolean();
for (const v of ["yes", "false", "", 0, 1]) {
  console.log(`coerce.boolean(${JSON.stringify(v)}) ->`, bool.parse(v));
}

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The boolean lines print what z.coerce.boolean() returns for each value, including the string "false". Code written by AgentGid [1].

Checked Oct 12, 2026: it starts without errors in Chromium with zod 4.6.6. Needs WebGL.

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