---
title: "diff Breaking Changes on npm | Since.dev"
description: "What each diff release removed, renamed or changed: 5 breaking changes in 1 version on npm, each with its source."
canonical_url: https://since.dev/packages/npm/diff
last_updated: 2026-04-13
---

# diff breaking changes

Every breaking API change we have recorded in diff on npm: 5 breaking changes in 1 version. Below are its newest version, removals and renames first, each with its source.

Newest change April 13, 2026

## 9.0.0

5 breaking changes, first published April 13, 2026.

- **Removed**  

The package no longer supports ES5 environments. Users who need ES5 must stay on version 8. [github.com](https://github.com/kpdecker/jsdiff/blob/v9.0.0/release-notes.md)
- **Behavior changed** `formatPatch`  

If oldFileName or newFileName is undefined, formatPatch now omits the file headers instead of writing the word undefined. [github.com](https://github.com/kpdecker/jsdiff/blob/v9.0.0/release-notes.md)
- **Behavior changed** `parsePatch`  

A patch with only a --- header or only a +++ header now causes parsePatch to throw. Patches with both headers or no headers are still accepted. [github.com](https://github.com/kpdecker/jsdiff/blob/v9.0.0/release-notes.md)
- **Signature changed** `StructuredPatch.newFileName`  

The oldFileName and newFileName fields are typed string | undefined instead of string, so code relying on string-only types may need to handle undefined. [npmjs.com](https://www.npmjs.com/package/diff/v/9.0.0)
- **Signature changed** `StructuredPatch.oldFileName`  

The oldFileName and newFileName fields are typed string | undefined instead of string, so code relying on string-only types may need to handle undefined. [npmjs.com](https://www.npmjs.com/package/diff/v/9.0.0)

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## Put your code on continuous management.

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---

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