HTTP Redirect Status Code Checker

2.0.0 · active · verified Wed Apr 22

is-redirect is a lightweight, focused utility package for JavaScript and TypeScript environments that efficiently determines if a given numeric HTTP status code falls within the 3xx redirection range. The current stable version is 2.0.0. As part of Sindre Sorhus's collection of focused utilities, it follows a pragmatic release cadence, with major versions typically signaling significant breaking changes, such as the recent transition to pure ESM. Its primary differentiator is its singular focus and minimal footprint, providing a reliable, dependency-free check for redirect status codes without including additional HTTP client or server logic. It serves as a fundamental building block for applications that need to interpret HTTP responses, such as proxies, web scrapers, or API clients, ensuring correct handling of redirect flows.

Common errors

```
Error [ERR_REQUIRE_ESM]: require() of ES Module .../node_modules/is-redirect/index.js from ... not supported.
```
cause Attempting to import `is-redirect` (v2.0.0+) using `require()` in a CommonJS module.

fix Change your import statement to `import isRedirect from 'is-redirect';` and ensure your file/project is configured for ESM (e.g., `"type": "module"` in `package.json`).
```
SyntaxError: Cannot use import statement outside a module
```
cause Using an `import` statement for `is-redirect` (v2.0.0+) in a JavaScript file that is being interpreted as a CommonJS module (e.g., a `.js` file without `"type": "module"` in `package.json` and not an `.mjs` file).

fix Either rename your file to `.mjs` or add `"type": "module"` to your project's `package.json` to enable ESM for `.js` files. Alternatively, if your project needs to remain CommonJS, downgrade `is-redirect` to version 1.x.

Warnings

breaking The package `is-redirect` is now pure ESM (ECMAScript Modules) starting from version 2.0.0. This means it can no longer be imported using CommonJS `require()` syntax.
Fix: Migrate your project to use ESM imports (`import isRedirect from 'is-redirect';`) or ensure your consuming module is also ESM. For Node.js, this often involves setting `"type": "module"` in your `package.json` or using `.mjs` file extensions.
breaking Version 2.0.0 and above of `is-redirect` requires Node.js version 12 or higher. Older Node.js versions will not be able to run this package.
Fix: Upgrade your Node.js environment to version 12 or newer. If you must support older Node.js versions, you will need to stick to `is-redirect@1.x`.
gotcha The package only checks for 3xx status codes commonly associated with redirects. It does not handle edge cases like `101 Switching Protocols` or `204 No Content` which might imply a redirect-like behavior in specific application contexts but are not strictly 3xx redirects.
Fix: For comprehensive HTTP status code handling beyond 3xx redirects, integrate `is-redirect` with other status code checking utilities or custom logic for different HTTP ranges (e.g., `is-success`, `is-server-error`).

Install

npm install is-redirect npm
yarn add is-redirect yarn
pnpm add is-redirect pnpm

Imports

isRedirect
wrong:
```
const isRedirect = require('is-redirect');
```
correct:
```
import isRedirect from 'is-redirect';
```
Package is pure ESM since v2.0.0; CommonJS `require` is no longer supported and will result in an `ERR_REQUIRE_ESM` error. Ensure your project is configured for ESM.
isRedirect (dynamic import)
wrong:
```
const isRedirect = await import('is-redirect');
```
correct:
```
const { default: isRedirect } = await import('is-redirect');
```
When dynamically importing, the default export is nested under a `default` property. Destructure correctly or access `importedModule.default`.
type IsRedirect
```
import type { IsRedirect } from 'is-redirect';
```
TypeScript users can import the type definition for the function if needed for advanced type-checking scenarios, though it's typically inferred.

Quickstart

Demonstrates how to use `is-redirect` to categorize different HTTP status codes, highlighting its primary function within a broader status checking logic.

import isRedirect from 'is-redirect';

function categorizeStatusCode(statusCode) {
  if (isRedirect(statusCode)) {
    console.log(`Status ${statusCode}: This is a redirect code.`);
    return 'redirect';
  } else if (statusCode >= 200 && statusCode < 300) {
    console.log(`Status ${statusCode}: This is a success code.`);
    return 'success';
  } else if (statusCode >= 400 && statusCode < 500) {
    console.log(`Status ${statusCode}: This is a client error code.`);
    return 'client-error';
  } else if (statusCode >= 500 && statusCode < 600) {
    console.log(`Status ${statusCode}: This is a server error code.`);
    return 'server-error';
  } else {
    console.log(`Status ${statusCode}: Uncategorized.`);
    return 'other';
  }
}

console.log('\n--- Testing various HTTP status codes ---');
categorizeStatusCode(301); // Moved Permanently
categorizeStatusCode(302); // Found
categorizeStatusCode(307); // Temporary Redirect
categorizeStatusCode(200); // OK
categorizeStatusCode(404); // Not Found
categorizeStatusCode(500); // Internal Server Error
categorizeStatusCode(100); // Continue

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