HTTP Headers Viewer

Inspect HTTP response headers including security, caching, and CORS headers

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📄What are HTTP Headers?

HTTP headers are metadata sent between a client (browser) and server with every HTTP request and response. They contain crucial information about the request/response, including content type, caching directives, security policies, and server information.

Headers are key-value pairs that control how browsers and servers communicate. Understanding headers is essential for web developers, security professionals, and anyone optimizing web performance.

Important HTTP Headers

Content-Type

Indicates the media type of the resource (e.g., text/html, application/json). Essential for browsers to correctly interpret the response.

Cache-Control

Directives for caching mechanisms. Controls how long resources are cached and whether they can be stored by intermediate proxies.

Content-Security-Policy

Prevents XSS attacks by specifying which sources are allowed for scripts, styles, images, and other resources.

Strict-Transport-Security

Forces browsers to use HTTPS for all future requests to the domain. Protects against protocol downgrade attacks.

Security Headers You Should Check

Security headers are critical for protecting your website and users from common attacks. Missing or misconfigured security headers can leave your site vulnerable to XSS, clickjacking, and other attacks.

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X-Frame-Options

Prevents clickjacking by controlling iframe embedding

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X-Content-Type-Options

Prevents MIME type sniffing attacks

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Referrer-Policy

Controls how much referrer information is sent

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Permissions-Policy

Controls which browser features can be used

Caching Headers for Performance

Proper caching headers can dramatically improve your website's performance by reducing server load and speeding up page loads for returning visitors. Understanding these headers is key to optimizing your site's speed.

Cache-Control is the primary header for caching. Common directives includemax-age (how long to cache),no-cache (revalidate before using), and no-store (never cache).

ETag and Last-Modified enable conditional requests, allowing browsers to check if a resource has changed without downloading it again. This saves bandwidth and improves perceived performance.