HTTP Header Checker

Introduction:

Hyper-text transfer protocol (HTTP) response headers convey status codes, caching rules and server metadata that browsers interpret before rendering a resource. Understanding these fields is vital for diagnosing redirect loops, security warnings and sluggish loads.

This tool sends a configurable request to any publicly reachable URL, then displays the status line, each returned header, redirect chain and total round-trip time. A ready-to-run curl command mirrors your settings for repeatable shell tests.

Use it to verify new cache rules after a deployment or to confirm that a mobile crawler sees the same headers as a desktop client. A remote origin may block or rate-limit frequent probes.

Technical Details:

Concept Overview

HTTP is a request–response protocol layered over TCP or TLS. Each server reply starts with a status line—protocol, numeric status and reason phrase—followed by colon-separated header fields that influence caching, compression, authentication and content negotiation. Analysing this metadata enables performance tuning and security hardening.

Request–Response Sequence

1. Resolve the domain to an IP address via DNS.
2. Open a TCP (or TLS) connection on port 80 or 443.
3. Send the chosen HEAD or GET request with any custom headers.
4. Receive the status line and header set #1.
5. Follow Location responses when redirects are allowed, repeating steps 2–4.
6. Aggregate every hop; expose the final set plus the full chain as prettified JSON.

Status-Code Classes

Only the last code in a redirect chain represents the resource ultimately shown to the user; intermediate codes guide user-agents silently.

Parameters

Worked Example

HTTP/1.1 200 OK
Cache-Control: max-age=604800
Content-Type: text/html; charset=UTF-8
Content-Length: 1256
Server: ECS (chi/55B2)

Assumptions & Limitations

• Relies on remote servers accepting standard ports.
• Cannot bypass firewalls or VPN-restricted endpoints.
• Compression sizes are not decompressed for bandwidth estimation.
• SSL verification follows the browser’s trust store.

Edge Cases & Error Sources

• HTTP /2 servers may coalesce headers into pseudo-fields.
• Chunked encoding with early termination returns incomplete header sets.
• Redirect loops exceed 10 hops and abort.
• CORS pre-flight failures on non-simple methods block JSON fetches.

Scientific Validity & References

Behaviour aligns with RFC 9110 (HTTP/1.1 semantics), RFC 9113 (HTTP/2) and the IANA HTTP Status Code Registry.

Privacy & Compliance

No personal data is required; requests are sent client-side and are subject to the same regulatory scope as ordinary browsing traffic.

Step-by-Step Guide:

Follow these steps to replicate any HTTP response under controlled conditions:

1. Enter the full resource URL in the main field.
2. (Optional) Expand Advanced to adjust method, user-agent or headers.
3. Click Check and wait until the timing badge appears.
4. Review the header Table or switch to Raw views for copy-pasting.
5. Copy or download the JSON payload for offline auditing.

FAQ:

Glossary:

Status Code

Three-digit result of an HTTP request.

Header Field

Key–value pair describing response metadata.

User-Agent

String identifying the requesting client.

Redirect

Server-initiated instruction to request a different URI.

TTL

Time-to-live; cache validity duration.