# What Are HTTP Security Headers? A Beginner's Guide
HTTP security headers are instructions sent by a web server to a browser. They can help control how a browser handles a website and reduce the risk of certain types of attacks and unwanted browser behavior.
Security headers are an important part of website security, but they are only one part of a complete security assessment.
## What Are HTTP Headers?
When a browser requests a web page, the server sends an HTTP response. This response can contain headers that provide information or instructions to the browser.
For example, a server can tell the browser how content should be loaded, whether a page may be displayed inside a frame, and how much referrer information should be sent.
Some headers are specifically useful for security.
## Why Are Security Headers Important?
Security headers can help website owners reduce certain browser-based security risks and improve the security configuration of their websites.
A website may work correctly even when some security headers are missing, but the missing configuration may still be worth reviewing.
Security headers should therefore be treated as part of a broader security assessment rather than as a complete security solution.
## Content-Security-Policy
Content-Security-Policy, commonly called CSP, allows a website to define which sources the browser should trust for different types of content.
A CSP can help control resources such as:
* JavaScript
* CSS
* Images
* Fonts
* Frames
* Connections
A properly designed CSP can reduce the impact of some cross-site scripting and other injection-related attacks.
However, CSP policies must be configured carefully because an overly restrictive policy can break legitimate website functionality.
## Strict-Transport-Security
Strict-Transport-Security, also known as HSTS, tells compatible browsers that a website should be accessed using HTTPS.
HSTS can help prevent certain downgrade and insecure-connection scenarios.
Before enabling HSTS, website owners should make sure their HTTPS configuration is working correctly and that all relevant services are prepared for HTTPS-only access.
## X-Content-Type-Options
The X-Content-Type-Options header can tell browsers not to MIME-sniff certain responses.
A commonly used value is:
`nosniff`
This can help reduce situations where a browser interprets a resource as a different content type than the server intended.
## X-Frame-Options
X-Frame-Options controls whether a page can be displayed inside a frame.
For example, a website may use it to reduce the risk of clickjacking.
Modern websites may also use the `frame-ancestors` directive in Content-Security-Policy for more flexible frame-control policies.
## Referrer-Policy
Referrer-Policy controls how much referrer information a browser sends when navigating from one page to another.
A suitable policy can reduce unnecessary exposure of URL information while still allowing normal website functionality.
Different websites may require different policies depending on their applications and analytics requirements.
## Permissions-Policy
Permissions-Policy allows websites to control access to certain browser features.
Depending on the browser and configuration, policies can restrict features such as:
* Camera
* Microphone
* Geolocation
* Fullscreen
* Other browser capabilities
Website owners should review which browser features their application actually needs and avoid unnecessarily exposing capabilities.
## How to Check Security Headers
A basic website security assessment can review the HTTP response headers returned by a website.
You can check whether important headers are present and then determine whether their values are appropriate for the website.
The important point is that a missing header does not automatically mean that the website is vulnerable. The impact depends on the website's architecture, functionality, and threat model.
## Common Security Header Checklist
A basic review can include:
* [ ] Content-Security-Policy
* [ ] Strict-Transport-Security
* [ ] X-Content-Type-Options
* [ ] X-Frame-Options or an appropriate CSP frame policy
* [ ] Referrer-Policy
* [ ] Permissions-Policy
The exact configuration should be reviewed according to the website's requirements.
## Security Headers Are Not Enough
Security headers cannot replace secure application development, authentication controls, access control, input validation, server security, patch management, or regular security testing.
For example, adding a security header will not fix a vulnerable application endpoint or an incorrectly configured database.
A complete website security assessment should consider multiple layers.
## Using Cyber Recon Pro
Cyber Recon Pro's Website Tester can help authorized website owners review publicly observable website security indicators, including HTTP security headers.
After making configuration changes, running another authorized test can help verify whether the expected headers are now being returned.
## Final Thoughts
HTTP security headers are an important part of modern website security.
Understanding headers such as Content-Security-Policy, Strict-Transport-Security, X-Content-Type-Options, X-Frame-Options, Referrer-Policy, and Permissions-Policy can help website owners identify configuration areas that deserve review.
Always test websites responsibly and only assess systems that you own or have explicit permission to test.