# About hydration-proof

> About hydration-proof: the open-source CLI and ESLint plugin for React hydration errors, its principles, its author, the MIT license and how to report issues.

Source: https://hydration.jscrate.dev/docs/about
Last updated: 2026-09-18

Everything about hydration-proof starts from one goal: find, explain and prevent
React hydration problems before users see them. It is an open-source project
with two npm packages, a CLI that tests every route of your app in a real
browser and an ESLint plugin that flags risky render code. Sohail Khan writes
it, under the MIT license.

## The two packages

| Package                         | What it does                                                                                                                                                                                                                                 | Start here                       |
| ------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------- |
| `hydration-proof`               | A CLI and Node API. It loads every route of a server-rendered React app in a real browser through Playwright, compares the server HTML with the hydrated DOM, and reports each difference with a stable issue code, a likely cause and a fix | [Quick start](https://hydration.jscrate.dev/docs/quick-start) |
| `eslint-plugin-hydration-proof` | 15 ESLint rules that catch hydration mismatches in render code while you write it                                                                                                                                                            | [ESLint plugin](https://hydration.jscrate.dev/docs/eslint)    |

Both are released together, at the same version; see [releases](https://hydration.jscrate.dev/docs/releases).

## Principles

- **Nothing is added to your app.** The CLI injects its runtime into the test
  browser only. Your code and build are not modified, and nothing ships in your
  production bundle.
- **No telemetry.** Nothing about your app, your run or your machine is
  uploaded: no analytics, no crash reporting, no version check.
- **No install scripts.** The package has no `postinstall` or other lifecycle
  script. Browsers are only downloaded when you run `hydration-proof install`.
- **One runtime dependency.** `playwright-core` is the only one, and it has none
  of its own. The ESLint plugin has no runtime dependencies.
- **Stable interfaces.** Issue codes, exit codes, the report schema and
  fingerprints do not change their meaning. From 1.0 on, the
  [compatibility promise](https://hydration.jscrate.dev/docs/compatibility) says what follows semver.
- **Every detection is proven.** Each detection has a fixture case: a broken
  page and a correct control, checked against React's own verdict. Every false
  positive that gets fixed becomes a recorded control page, so it cannot come
  back.

## Who makes it

hydration-proof is written by [Sohail Khan](https://me.jscrate.dev). The source
is on GitHub at
[re-sohail/hydration-proof](https://github.com/re-sohail/hydration-proof), and
this site is its documentation.

Both packages are released under the MIT license, copyright Sohail Khan.

## Questions about hydration-proof

### Report a bug or ask for a feature

Open an issue on
[GitHub](https://github.com/re-sohail/hydration-proof/issues). A bug report
with a minimal reproduction is the most valuable contribution: include the
version, the command you ran and the output. The
[troubleshooting](https://hydration.jscrate.dev/docs/troubleshooting) page covers the common problems first.

### Report a security issue

Report vulnerabilities privately through
[GitHub security advisories](https://github.com/re-sohail/hydration-proof/security/advisories/new),
not in public issues. Include the version, the command you ran and, if you can,
an app that shows the problem. You get a first reply within a week, and security
fixes are released for the latest minor version. [Security](https://hydration.jscrate.dev/docs/security)
describes what hydration-proof does with your app's data.

### Contribute

[CONTRIBUTING.md](https://github.com/re-sohail/hydration-proof/blob/main/CONTRIBUTING.md)
has the setup and the checks to run. Contributions follow a few rules:

- No new runtime dependencies. Use Node built-ins or write the code.
- A new detection needs a fixture case, a broken page and a correct control,
  and must keep detection at 100% with 0 false positives.
- A user-visible change needs a changeset that describes it for the changelog.

## Related

- [How hydration-proof detects mismatches](https://hydration.jscrate.dev/docs/how-it-works)
- [Releases and changelog](https://hydration.jscrate.dev/docs/releases)
- [Compatibility and stability](https://hydration.jscrate.dev/docs/compatibility)
- [Security and your app's data](https://hydration.jscrate.dev/docs/security)
- [Quick start](https://hydration.jscrate.dev/docs/quick-start)