Rare find

Ow. Check that function inputs are the right type before your code breaks.

sindresorhus.com/ow

Problem

The full read on this project is a sign-in away — what it solves, who it serves, and where it sits in the market.

Audience

The full read on this project is a sign-in away — what it solves, who it serves, and where it sits in the market.

Market

The full read on this project is a sign-in away — what it solves, who it serves, and where it sits in the market.

Pricing

The full read on this project is a sign-in away — what it solves, who it serves, and where it sits in the market.

Vaya's read on this project

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Updates

October 2025

Release — Oct 16
3.1.1 Oct 16
Prevent publishing broken builds Oct 16
Fix CI Oct 10
Release — Oct 10
3.1.0 Oct 10
Update dependencies Oct 10
Add tests for const value validation patterns Oct 10
Add `ow.validate()` method that returns validation results without th… Oct 9
Fix `ow.any()` not working in collection shape methods Oct 9
Fix type narrowing not working with reusable validators Oct 9
Add `.absent` modifier for optional object properties Oct 9
Add `.custom()` method Oct 9

September 2025

Add `isPredicate` function for programmatic predicate identification Sep 10
Add `string.email` predicate Sep 10
Add `nullable` modifier Sep 10
Add 'Why use Ow?' section and practical examples Sep 10
Release — Sep 9
3.0.0 Sep 9
Require Node.js 20 Sep 9
Add TypeScript literal type narrowing for `string.equals()` and `stri… Sep 9
Improve performance of shape validation with optional properties Sep 9
Use modern TypeScript syntax Sep 9

May 2024

Release — May 5

January 2023

Release — Jan 26

October 2022

Release — Oct 3
Release — Oct 3

June 2022

Release — Jun 13

October 2021

Release — Oct 4

September 2021

Release — Sep 22