HTTP Headers Viewer

View all HTTP headers sent with your request. Debug CORS, caching, authentication, and security headers instantly.

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What are HTTP headers?

HTTP headers are metadata sent with every HTTP request and response. They carry information about the request, the client, caching preferences, security policies, and more. Headers are key-value pairs that look like:

Content-Type: application/json
Authorization: Bearer abc123
Cache-Control: max-age=3600

Common request headers

Host - The domain being requested:

Host: www.example.com

User-Agent - Identifies the browser/client:

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) Chrome/120.0

Accept - Content types the client can handle:

Accept: text/html,application/json

Accept-Language - Preferred languages:

Accept-Language: en-AU,en;q=0.9

Accept-Encoding - Supported compression:

Accept-Encoding: gzip, deflate, br

Security headers

Origin - Where the request originated (for CORS):

Origin: https://app.example.com

Sec-Fetch-* - Request context for security decisions:

Sec-Fetch-Dest: document
Sec-Fetch-Mode: navigate
Sec-Fetch-Site: same-origin

Authorization - Authentication credentials:

Authorization: Bearer eyJhbGciOiJIUzI1...
Authorization: Basic dXNlcjpwYXNz

Caching headers

Cache-Control - Caching directives:

Cache-Control: no-cache
Cache-Control: max-age=3600

If-Modified-Since - Conditional request (304 Not Modified):

If-Modified-Since: Wed, 21 Oct 2024 07:28:00 GMT

If-None-Match - Conditional request using ETag:

If-None-Match: "abc123"

Client hints

Modern browsers send Client Hints for adaptive content:

Sec-CH-UA: "Chrome";v="120"
Sec-CH-UA-Mobile: ?0
Sec-CH-UA-Platform: "Windows"

These help servers deliver optimised content without parsing the User-Agent string.

Debugging with headers

CORS issues - Check Origin header matches server expectations.

Authentication failures - Verify Authorization header is present and formatted correctly.

Caching problems - Look for Cache-Control, If-Modified-Since, If-None-Match.

Mobile detection - Check Sec-CH-UA-Mobile or parse User-Agent.

Headers through proxies

When requests pass through proxies, load balancers, or CDNs, additional headers track the original client:

X-Forwarded-For - Client IP through proxies:

X-Forwarded-For: 203.0.113.50, 70.41.3.18

X-Real-IP - Single original client IP:

X-Real-IP: 203.0.113.50

X-Forwarded-Proto - Original protocol:

X-Forwarded-Proto: https

How this tool works

This tool displays all HTTP headers your browser sends when loading this page. Headers are categorised by type for easy navigation. Sensitive values (cookies, auth tokens) are partially masked. You can copy all headers as text or JSON. Powered by a QuantCDN Edge Function running at the edge nearest to you.