redirect-sentinel

Find open redirects and mixed content in a built site (offline) or a live crawl: http:// scripts and styles on HTTPS pages, insecure forms, client-side redirects fed by the URL, open redirect rules in _redirects/vercel.json/nginx, HTTPS downgrades, and optional safe redirect probing.

Point redirect-sentinel at your build output (dist/, public/, _site/) in CI, or at a URL to crawl the live site. CLI, library and GitHub Action. Node.js 18+, zero runtime dependencies. Broken links are out of scope (see static-link-sentinel).

What it checks

Mixed content on HTTPS pages: http:// scripts, stylesheets, @import, iframes, objects and <base> (active, high); images, srcset, media, icons and CSS url() (passive, medium); forms posting to http://; http:// links (low, once per host). localhost URLs are ignored. Use --http if the static site is not served over HTTPS.
Client-side open redirects: location = …, location.assign/replace, window.open, router.push, navigate fed by location.search/hash, URLSearchParams, document.referrer or window.name, directly or through a variable. Redirects guarded by startsWith('/') or an origin check are skipped. This is a heuristic, not a data-flow engine: minified bundles are only checked for direct flows.
Server redirect rules: Netlify _redirects and netlify.toml, vercel.json/next.config.js, nginx (return 302 $arg_url) and Apache (RewriteRule … %1 [R]) rules whose destination host comes from the request.
Links that pass a full URL in a redirect-style parameter (next, url, returnTo, redirect_uri, continue, goto…).
Crawl only: redirect chains longer than 3 hops, https:// → http:// downgrades (including meta refresh), http:// not redirecting to https://, and same-origin JavaScript files.
--probe (crawl only, opt-in): for each same-origin link with a redirect-style parameter, requests it with https://redirect-sentinel.invalid/, //redirect-sentinel.invalid/ and similar payloads, without following the redirect. A Location pointing at that host is a confirmed open-redirect (critical). .invalid can never resolve, so nobody is sent anywhere. Only probe sites you own or are authorised to test.

Rules

Rule	Default	Meaning
`open-redirect`	critical	Confirmed open redirect: a parameter sends visitors to any site
`open-redirect-js`	high	Client-side redirect or window.open fed by URL, hash or referrer
`open-redirect-config`	high	Redirect rule sends visitors to a host taken from the request
`mixed-content-active`	high	HTTPS page loads a script, stylesheet, frame or object over http://
`redirect-downgrade`	high	Redirect goes from https:// to http://
`insecure-form`	high	Form posts to an http:// URL
`mixed-content-passive`	medium	HTTPS page loads an image, audio or video over http://
`http-no-redirect`	medium	http:// version of the site does not redirect to https://
`redirect-param`	medium	Link passes a full URL in a redirect-style parameter (next, url, returnTo…)
`meta-refresh-external`	low	Meta refresh redirects to another site
`insecure-link`	low	Link to an http:// URL
`redirect-chain`	low	Redirect chain longer than 3 hops
`fetch-error`	low	Page could not be fetched

Install and run

npx redirect-sentinel dist/                            # offline, in CI after the build
npx redirect-sentinel https://staging.example.com --max-pages 200
npx redirect-sentinel https://staging.example.com --probe --fail-on high

Library

import { check, analyzeHtml, analyzeJs } from 'redirect-sentinel';
const report = await check(['dist'], { severity: { 'insecure-link': 'off' } });

Configuration

Put a .redirect-sentinel.json in the working directory (or pass --config <file>). Every key is optional; CLI flags override the file.

{
  "failOn": "high",
  "severity": { "insecure-link": "high" },
  "allow": [
    { "rule": "insecure-link", "match": "http://partner.example.org*", "reason": "Accepted risk, ticket SEC-123", "expires": "2027-03-31" }
  ]
}

severity changes the severity of any rule, or turns it off.
allow suppresses findings. Each entry needs a rule (globs such as insecure-* work) and a reason, and can be narrowed with target and match (a glob tested against the target, location and value). Suppressed findings are listed in the JSON report. When expires (YYYY-MM-DD) has passed, the finding comes back together with an allow-expired finding, so exceptions can't be forgotten. Entries that match nothing are reported as allow-unused (info).

Output and exit codes

--format text|json|sarif|markdown for stdout, plus --json, --sarif and --markdown <file> to write extra copies in one run. SARIF 2.1.0 works with GitHub code scanning.
--fail-on critical|high|medium|low|info|none (default high).
Exit code 0: passed. 1: at least one finding at or above --fail-on. 2: usage or config error, or a target could not be checked.
--list-rules prints every rule with its default severity.

GitHub Action

permissions:
  contents: read
  security-events: write   # only for the SARIF upload
steps:
  - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
    with: { persist-credentials: false }
  - uses: MrLouisWright/redirect-sentinel@v1
    with:
      targets: 'dist'
      fail-on: high
      sarif: redirect-sentinel.sarif
  - uses: github/codeql-action/upload-sarif@v3
    if: always()
    with: { sarif_file: redirect-sentinel.sarif }

Inputs: targets, fail-on, config, sarif, json, job-summary (Markdown report in the job summary, default true), args (extra CLI flags), max-pages, probe. Outputs: markdown-file, exit-code.

Requirements

Node.js 18 or newer. No runtime dependencies.

Support

If this project is useful to you, you can support its development with a donation: Buy me a coffee. It helps keep these tools maintained, documented and free for everyone.

Credit (optional)

Free to use under MIT, no attribution required. If redirect-sentinel helps you, a link back is appreciated:

<a href="https://louiswright.co.uk">Built with redirect-sentinel by Louis Wright</a>

[![Built with redirect-sentinel by Louis Wright](https://img.shields.io/badge/built%20with-redirect--sentinel-blue)](https://louiswright.co.uk)

Safe redirect helpers

import { safeRedirectUrl, safeRedirectMiddleware, nextSafeRedirect } from 'redirect-sentinel';

// Express
app.use(safeRedirectMiddleware({ allowedHosts: ['.example.com'], fallback: '/' }));
app.get('/login/done', (req, res) => res.safeRedirect(req.query.next));

// Next.js middleware / route handler
return NextResponse.redirect(new URL(nextSafeRedirect(req.nextUrl, 'next'), req.url));

Relative paths are allowed. Absolute URLs pass only when they are HTTPS and on allowedHosts (a leading . also allows subdomains). Code that uses these helpers isn't reported by open-redirect-server.

Server code and config analysis

open-redirect-server flags res.redirect(req.query.next), NextResponse.redirect(new URL(searchParams.get('to'), req.url)), redirect(searchParams.get(...)) and Location headers set from the request, in JS and TS.
Next.js redirects() flags destinations such as ':dest*' and 'https://:host/', including hosts driven by has: [{ type: 'query', key: 'host' }].
nginx flags return 301 $arg_url; and return 302 https://$arg_host/;, plus variables built from $arg_* or $http_referer through map or set.

This tool only covers redirects and mixed content on your own site. Use header-sentinel and csp-forge for headers and CSP.

Module formats and types

Ships ESM (import) and a bundled CommonJS build (require), with TypeScript declarations generated from the source:

import * as lib from 'redirect-sentinel';      // ESM
const lib = require('redirect-sentinel');      // CommonJS

Tests live in test/ and run on Node 18, 20 and 22 in GitHub Actions, including a require+import check. Releases are published with npm publish --provenance.

redirect-sentinel