ProperHeader – Modify Headers, Redirects & File Overrides

Edit request/response headers, redirect or block requests, override JS/CSS. Readable code, no tracking. Imports ModHeader profiles.

Modify request and response headers, redirect URLs and override JavaScript, CSS and JSON files in Chrome. No tracking, no remote code, and unminified source you can read. ProperHeader is a header and request editor for web developers, QA testers and anyone who needs Chrome to send or receive something slightly different. Set an Authorization token, fix CORS on localhost, strip a Content-Security-Policy, point production JavaScript at your dev server, or mock an API response, then switch it all off with one click. ━━━━━━━━━━━━━━━━━━━━ WHAT YOU CAN DO ━━━━━━━━━━━━━━━━━━━━ ★ Request headers Set, append or remove any request header: Authorization and Bearer tokens, API keys, User-Agent, Accept-Language, cookies, feature flags and debug headers. Header names autocomplete as you type. ★ Response headers (Pro) Change headers before the page sees them. Fix CORS for local development, remove or rewrite Content-Security-Policy, and turn off caching. ★ Profiles Keep named sets of rules such as "Local dev", "Staging API" or "Mobile user agent", and switch between them from the toolbar in one click. The toolbar badge always shows what's active. (Free includes one profile; Pro is unlimited.) ★ URL filters (Pro) Choose exactly which requests a rule touches: wildcard, "contains", exact or regex matching, exclusions, and resource types (scripts, XHR/fetch, images, documents and more). ★ Redirects and blocking (Pro) Send a production script to http://localhost, use regex redirects with $1 capture groups, or block requests outright. ★ File overrides (Pro) Replace a JavaScript, CSS, JSON or HTML response with your own text. It's the job Resource Override used to do, rebuilt for Manifest V3. ★ CSS and JavaScript injection (Pro) Add your own styles or scripts to the sites you choose. ★ Quick-start recipes Common setups in one click: Bearer token, mobile User-Agent, language testing, CORS for localhost, disable caching, strip CSP, prod JS to localhost, and mock an API response. ★ Pause everything instantly Flip the main switch in the popup, or press Alt+Shift+H, to stop all modifications at once. Turn it back on and everything is restored. ★ Import and export Back up your rules to a JSON file or move them to another computer. You can import ModHeader profile exports directly (see below). ━━━━━━━━━━━━━━━━━━━━ BUILT FOR THE JOBS YOU DO EVERY DAY ━━━━━━━━━━━━━━━━━━━━ • Fix "blocked by CORS policy" errors while developing against a real API • Send a Bearer token or API key on every request to a staging server • Turn on feature flags or debug headers without changing code • Load your local development build on the live production site • Test how a site behaves in another language or on a mobile User-Agent • Return mock JSON from an endpoint that isn't built yet • Remove a Content-Security-Policy that blocks your debugging tools • Make sure you always get fresh, uncached responses ━━━━━━━━━━━━━━━━━━━━ PRIVACY BY CONSTRUCTION ━━━━━━━━━━━━━━━━━━━━ A header extension can see your web traffic, so you should be able to check what it does with it. ProperHeader is built to be easy to audit. • Nothing leaves your browser. No analytics, no telemetry, no ads and no remote code. Your rules are stored locally in Chrome. • On the free plan ProperHeader makes no network requests at all. • Pro checks your licence with ExtensionPay (extensionpay.com), and that is the only server the extension can talk to. Chrome enforces this through the extension's Content Security Policy, so it isn't just a promise. • The code is plain, unminified JavaScript. Every line Chrome runs is readable. • No site access until you grant it. ProperHeader asks for permission on the sites you choose, or on all sites if you prefer, and you can withdraw it at any time. • Rules use Chrome's built-in declarativeNetRequest engine, so requests are changed by Chrome itself, quickly and without the extension reading page content. ━━━━━━━━━━━━━━━━━━━━ COMING FROM MODHEADER? ━━━━━━━━━━━━━━━━━━━━ Export your profiles from ModHeader (or use a JSON file you saved earlier), then open ProperHeader → Settings → Import / Export → Import. • Request and response headers, URL filters, resource types and redirects convert automatically. • Disabled headers stay disabled. • Anything that can't be converted is listed after import, so nothing disappears silently. ProperHeader is an independent project and is not affiliated with or endorsed by ModHeader. ━━━━━━━━━━━━━━━━━━━━ PRICING ━━━━━━━━━━━━━━━━━━━━ FREE, forever • 1 profile • Unlimited request headers • Import, export and ModHeader import • Pause switch, keyboard shortcut and toolbar badge • No network calls at all PRO, $3 per month or $36 once for lifetime access • Everything in Free • Unlimited profiles • Response headers (CORS, CSP, caching) • URL filters, regex and exclusions • Redirects and request blocking • JavaScript, CSS, JSON and HTML file overrides • CSS and JavaScript injection Payments are handled by ExtensionPay with Stripe. ProperHeader never sees your card details. Already paid on another computer? Use "Restore purchase". ━━━━━━━━━━━━━━━━━━━━ GOOD TO KNOW ━━━━━━━━━━━━━━━━━━━━ • File overrides work by redirecting the file to a data: URL. If a site's Content-Security-Policy forbids that, Chrome refuses it. Turn on "Remove CSP" for that site and the override works while your profile is on. • Each overridden file can be up to about 1.4 MB, and an overridden response is always HTTP 200 with only a Content-Type header. • JavaScript injection needs Chrome's "Allow User Scripts" setting. Switch it on once in chrome://extensions → ProperHeader → Details. CSS injection needs no extra step. • Requests answered from a site's service-worker cache never reach the network, so no extension can change them. ━━━━━━━━━━━━━━━━━━━━ GETTING STARTED ━━━━━━━━━━━━━━━━━━━━ 1. Click the ProperHeader icon in the toolbar. 2. Pick a quick-start recipe or add a header. 3. Allow ProperHeader on the site you're working on. 4. Reload the page. That's it. For URL filters, redirects, overrides and more, click "Full editor" or "Settings". Privacy policy: https://properheader.com/privacy/ Website and support: https://properheader.com/ Contact: richardmacarthy@protonmail.com Made by RJ Macarthy, an independent developer in the UK.