react-diff-view is an MIT-licensed React component, maintained by otakustay, that consumes git unified diff output and renders it as a readable side-by-side or unified diff in the browser. If you are building a code review UI, a pull request viewer, or any tool that shows changes between two versions of a file, it saves you from parsing and styling diffs yourself. This guide covers how it fits together and, more importantly, the security considerations when the diffs you render come from untrusted sources.
The package pairs a parser with rendering components. You feed it the text output of git diff, it parses that into a structured representation, and the components render hunks, lines, and gutters with GitHub-style theming. As of recent releases it sits at version 3.x, ships an unminified ESM build you can import from react-diff-view/esm, and keeps its styling in a separate stylesheet you import explicitly.
How the Rendering Pipeline Works
The typical flow has two stages. First you parse a diff string with parseDiff, which wraps the gitdiff-parser package and returns an array of file objects. Then you pass each file's hunks to the Diff and Hunk components for rendering.
import { parseDiff, Diff, Hunk } from 'react-diff-view';
import 'react-diff-view/style/index.css';
function DiffViewer({ diffText }) {
const files = parseDiff(diffText);
return files.map(({ oldRevision, newRevision, type, hunks }) => (
<Diff key={oldRevision + '-' + newRevision} viewType="split" diffType={type} hunks={hunks}>
{(hunks) => hunks.map((hunk) => <Hunk key={hunk.content} hunk={hunk} />)}
</Diff>
));
}
The docs recommend generating your diff with git diff -U1 for the cleanest display, and the component exposes options for gutters, line decorations, and widgets you can inject between lines for inline comments. That widget system is what makes it suitable for full review interfaces.
Where the Security Considerations Sit
react-diff-view itself is a rendering library, and its job is to display text. The risk is not usually in the component; it is in what you render and how. Two questions decide your exposure.
First, where does the diff come from? If you render diffs of your own repositories in an internal tool, the trust level is high. If you render diffs submitted by users, from public repositories, or from external systems, that content is untrusted. Diff content includes file contents, and file contents can contain anything, including strings that look like markup.
Second, do you ever render diff content as HTML? The library renders line content as text by default, which is the safe path. Problems appear when developers add custom tokenization, syntax highlighting, or widgets that take the raw line string and inject it into the DOM as HTML rather than text. That reintroduces the cross-site scripting risk the default rendering avoids. If you add syntax highlighting, use a highlighter that outputs sanitized, structured tokens rather than one that returns raw HTML strings you dangerously set.
Keeping Custom Extensions Safe
The widget and token APIs are powerful, which means they are also where you can undo the library's safety. A few rules:
- When you render tokens or widgets, prefer React elements and
textContent-style rendering overdangerouslySetInnerHTML. - If a syntax highlighter returns HTML, run it through a sanitizer like DOMPurify before injecting, or switch to a token-based highlighter.
- Treat file paths in the diff as untrusted too; a crafted path could contain markup if you render it into a header without escaping.
None of this is specific to react-diff-view. It applies to any component that displays externally sourced content. The library gives you a safe default; custom code is where teams reintroduce risk.
Managing It as a Dependency
Beyond usage, treat react-diff-view like any npm dependency in your supply chain. It pulls in gitdiff-parser and expects React as a peer dependency, so its transitive footprint is small, but "small" is not "zero." Known vulnerabilities can appear in any package or its dependencies over time, so pin versions, review updates, and scan continuously rather than assuming a small library is a safe one.
Lockfile hygiene matters here. Commit your package-lock.json or yarn.lock so every build resolves the exact same tree, and review dependency updates in pull requests instead of letting them float. An SCA tool can flag a newly disclosed issue in react-diff-view or its dependencies transitively, so you learn about it from your pipeline rather than from an incident. For the broader picture of why transitive dependencies deserve this attention, our dependency security guidance walks through the supply chain reasoning.
When to Reach for It
react-diff-view is a good fit when you need a maintained, well-themed diff renderer and do not want to build parsing and layout yourself. It is MIT licensed, actively maintained, and battle-tested in code review interfaces. The main thing to get right is the trust boundary: render text as text, sanitize anything you turn into HTML, and keep the dependency patched. Do those three things and the component is a solid, low-risk choice.
FAQ
Is react-diff-view safe to use with untrusted diffs?
By default it renders line content as text, which avoids cross-site scripting. The risk appears when you add custom tokenization, syntax highlighting, or widgets that inject raw HTML. Keep custom rendering token-based or run it through a sanitizer, and rendering untrusted diffs is safe.
What does react-diff-view depend on?
It wraps gitdiff-parser for parsing and expects React as a peer dependency. The transitive footprint is small, but you should still pin versions, commit your lockfile, and scan for newly disclosed vulnerabilities like any other dependency.
What license is react-diff-view under?
It is MIT licensed and maintained by otakustay on GitHub, which makes it straightforward to use in most commercial and open source projects. Always confirm the license in your current version before relying on it.
How should I generate diffs for react-diff-view?
The documentation recommends git diff -U1 for the cleanest display, then parsing the output with the library's parseDiff function before passing hunks to the Diff and Hunk components.