HTTP security headers checklist for web apps

When someone visits your site, your server replies with the page and a set of headers — extra instructions the browser reads but the visitor never sees. Security headers use that channel to tell the browser to be stricter: stay on HTTPS, refuse to be embedded elsewhere, and only load content from places you trust.

AI builders often skip these because a demo works fine without them. They are worth setting because they are cheap, they apply to every visitor automatically, and they blunt whole categories of browser-based attacks. This page stays practical on purpose — it is a launch checklist, not an exhaustive specification of every header and directive.

Confirm these on your live site before launch. You are checking that each protection is present and reasonable, not tuning every option perfectly.

• HTTPS is enforced and HTTP requests redirect to HTTPS.

• A strict-transport policy tells browsers to stay on HTTPS.

• Framing protection prevents other sites from embedding your app.

• A content policy restricts where scripts and other content can load from.

• Content-type guessing is disabled so files are treated as their declared type.

• Referrer information sent to other sites is limited to what you need.

• Browser feature access (camera, location, etc.) is restricted to what your app uses.

These headers exist to protect your users inside their browser. A plain definition: a browser-facing protection reduces what a malicious page or injected script can do to someone already using your site.

• Content-type protection stops the browser from reinterpreting a file as something more dangerous.

• Referrer control limits how much of your URLs leak to third-party sites.

• Feature/permissions control limits access to sensitive browser capabilities.

Clickjacking is when an attacker loads your site invisibly inside their own page and tricks a user into clicking something they did not intend. Framing protection tells the browser whether — and by whom — your site is allowed to be embedded.

• Your app refuses to be embedded by sites you do not control.

• If embedding is needed, only specific trusted origins are allowed.

• Sensitive actions are not reachable from inside an embedded frame.

A content policy (commonly a Content-Security-Policy, or CSP) tells the browser which sources of scripts, styles, and other content it should trust. A good policy limits the damage if a malicious script ever gets onto your page.

• Scripts and content load only from sources you trust.

• Inline and arbitrary remote scripts are limited rather than allowed everywhere.

• Introduce a content policy gradually and test that legitimate content still loads.

HTTPS encrypts traffic between the browser and your server. Enforcing it — and telling browsers to stay on it — prevents users from being silently downgraded to an unencrypted connection.

• Your site is served over HTTPS with a valid certificate.

• HTTP requests redirect to HTTPS rather than serving content.

• A strict-transport policy instructs browsers to use HTTPS automatically.

• There is no mixed content — pages do not load resources over plain HTTP.

Modern browsers can grant pages access to the camera, microphone, location, and more. If your app does not use a capability, the safest setting is to deny it, so a compromised or injected script cannot request it on your behalf.

• List the browser features your app actually uses.

• Restrict or deny access to features you do not use.

• Re-check after adding features that need new permissions.

GuardMint reads the headers your live site sends — the same ones any browser receives — and reports which protections are missing or look misconfigured. Our methodology explains how the public scan works.

• Whether HTTPS is enforced and a strict-transport policy is present.

• Whether framing protection is set.

• Whether a content policy and content-type protection are present.

• Whether referrer and permissions controls are reasonable.

Headers are a visible baseline, but their presence does not mean your app is safe. The items below live below the surface and need manual or code review.

• Whether your authentication and authorization are correct.

• Whether your database blocks access to other users' data.

• Whether secrets are kept out of your frontend bundle.

• Whether a content policy is actually tuned for your app, not just present.

What are HTTP security headers?

HTTP security headers are instructions your server sends with each response that tell the browser how to handle your site more safely — for example, to enforce HTTPS, to refuse being embedded in another site, or to restrict where content can load from. They are a browser-facing baseline that reduces the impact of common attacks.

Which HTTP security headers matter most before launch?

The highest-value protections are enforcing HTTPS, preventing your app from being framed by other sites, restricting where scripts and content can load from, and stopping the browser from guessing content types. Getting these right covers most of the practical risk for a small web app.

Do security headers make my app secure?

No. Headers reduce the impact of certain browser-based attacks, but they do nothing for backend problems like weak authentication, open database rules, or exposed secrets. Treat them as one layer of a launch-readiness baseline, not as proof your app is secure.

Can GuardMint check my security headers?

Yes. Because headers are sent with every public response, GuardMint can see them from the outside and report which protections are missing or look misconfigured. It checks presence and reasonableness, not whether a strict policy is perfectly tuned for your specific app.

Will a strict Content-Security-Policy break my app?

It can if you add it all at once, because a strict policy blocks anything it does not explicitly allow. The practical approach is to get the simpler protections in place first, then introduce a content policy gradually and test that legitimate scripts, styles, and images still load.

Are headers enough to pass a security review?

No. Headers are a visible, easy-to-check baseline, but a real review also covers authentication, authorization, data exposure, and platform configuration. Headers being present is a good sign, not a complete answer.