HTTP Headers Viewer

View HTTP response headers instantly with live preview and redirect tracking.

HTTP Headers Viewer

Fetch and inspect response headers with live preview, redirects, and copy/download.

Request

Tip: try a mobile or crawler User-Agent if the site varies responses.
Live preview updates automatically as you type.
Requests are performed server-side. For private endpoints or credentials, use an internal secure environment.

Result

Enter a URL and the tool will display:
  • Status code and final URL
  • Redirect chain header blocks
  • Formatted header list + raw header text

About HTTP Headers Viewer

HTTP Headers Viewer Tool – HTTP Response Header Checker

Need to see exactly what a website sends back to browsers, bots, and APIs? This HTTP Headers Viewer tool lets you fetch and inspect HTTP response headers for any public URL so you can troubleshoot caching, redirects, cookies, security policies, and CDN behavior. With live preview, you can tweak settings (method, redirects, user agent) and immediately see how the headers change.

Headers are the “control plane” of the web: they describe content type, compression, cache rules, security constraints, and the server’s decisions around redirects and authentication. When something breaks—assets not caching, CORS errors, mixed content warnings, login loops—headers are usually the fastest path to the root cause.

How It Works

This tool performs an HTTP request to the URL you provide and captures the response headers returned by the remote server. You can choose a lightweight HEAD request (fetch headers only) or a standard GET request (headers plus a tiny, discarded body read). If you enable redirect following, the tool will track the redirect chain and display each hop’s header block, so you can see where the final response comes from.

Step-by-step process

  • 1) Validate URL and options: The tool checks that your input is a valid URL and that chosen options (method, toggles) are allowed.
  • 2) Send request with cURL: A request is made using safe defaults (timeouts, a configurable User-Agent, TLS verification).
  • 3) Capture header blocks: The raw response header text is collected, including intermediate redirects when enabled.
  • 4) Parse and format: Each header block is separated, the status line is extracted, and headers are grouped for easy reading.
  • 5) Render live preview: While you type or change options, the preview updates automatically without a full page reload.

Key Features

Live preview without page reload

The result panel updates automatically as you edit the URL or options. This makes it easy to compare behavior across endpoints, environments, or CDN configurations.

Redirect chain visibility

When redirects are enabled, you can see each HTTP hop (301/302/307/308) with its own status line and headers. This helps diagnose canonicalization issues (http → https), trailing slash rules, locale redirects, and cookie scoping problems.

HEAD or GET request modes

Use HEAD to test headers quickly with minimal bandwidth, or use GET if the origin behaves differently for HEAD requests (some stacks do). The tool discards body data to keep things fast.

Custom User-Agent

Some sites vary responses based on device or bot detection. Set a custom User-Agent to inspect the exact headers served to browsers, crawlers, or monitoring agents.

Copy and download

Copy the formatted output to your clipboard, or download it as a text file for bug reports, documentation, or collaboration with DevOps and security teams.

Use Cases

  • Debug caching and CDN behavior: Verify Cache-Control, ETag, Last-Modified, and Age when assets refuse to cache or revalidate too often.
  • Troubleshoot redirect loops: Inspect Location headers and cookie scopes to find loops between http/https, www/non-www, or app/login routes.
  • Check security headers: Validate Content-Security-Policy, X-Frame-Options, Strict-Transport-Security, and Permissions-Policy before shipping to production.
  • Validate CORS for APIs: Confirm Access-Control-Allow-Origin, Access-Control-Allow-Methods, and related headers during frontend integration.
  • Cookie audits: Review Set-Cookie flags like Secure, HttpOnly, and SameSite when login or session persistence breaks.
  • SEO and crawling checks: Ensure the correct canonical redirects, consistent status codes, and content negotiation via Vary.
  • Uptime and monitoring verification: Confirm that health endpoints return expected status codes and headers quickly and consistently.

In short, if your browser’s Network tab is too noisy or you need a server-side, reproducible way to inspect header responses, this tool gives you a clean, shareable report.

Optimization Tips

Prefer HEAD for quick checks

Start with the HEAD method to validate redirect behavior, cache headers, and security policies using minimal data transfer. Switch to GET only when you suspect the origin handles HEAD differently.

Compare with and without redirects

Run the same URL twice—once with redirects disabled and once enabled. This quickly reveals whether a proxy or application layer is rewriting headers in later hops.

Test multiple User-Agents

If you rely on device-specific delivery or bot rules, test a few realistic User-Agents (desktop browser, mobile browser, crawler). Differences often reveal hidden configuration branches.

FAQ

HEAD requests return headers only, which is faster and uses less bandwidth. GET requests return headers plus a response body. This tool discards body bytes, but some servers still behave differently for GET vs HEAD, so GET can be useful for edge cases.

Multiple blocks usually indicate redirects. Each hop can add or change headers, especially when moving from HTTP to HTTPS, or from an edge/CDN to the origin.

This viewer is designed for public URLs. If an endpoint requires authentication, the server may respond with 401/403 and related headers. For private systems, use your internal tooling or a secure environment that can add credentials safely.

Start with Cache-Control, Expires, ETag, Last-Modified, Vary, and Age. Also check the status code (200 vs 304) and whether a CDN adds headers like X-Cache or Via.

The tool performs a real network request to the target host. Response time depends on DNS, TLS negotiation, server load, and redirect chains. Timeouts are used to keep the experience responsive.

Header Fields You’ll Commonly Inspect

Content and encoding

When pages render incorrectly or downloads open with the wrong application, look at Content-Type and Content-Disposition. If compression is misconfigured, Content-Encoding and Transfer-Encoding will usually tell the story. For APIs, verifying Content-Type: application/json (and correct charset) prevents subtle parsing bugs.

Caching and revalidation

CDNs and browsers rely on Cache-Control directives such as max-age, s-maxage, public/private, and no-store. Validators like ETag and Last-Modified influence whether clients receive 304 Not Modified responses. If you see frequent re-downloads, confirm that revalidation headers are stable and that Vary is not too broad.

Security posture

Modern hardening often starts with headers: Strict-Transport-Security for HTTPS enforcement, Content-Security-Policy for script/style restrictions, and X-Content-Type-Options to prevent MIME sniffing. If embedded content fails, check X-Frame-Options or CSP’s frame-ancestors. For privacy controls, Permissions-Policy and Referrer-Policy are key.

Cross-origin rules

CORS issues can be hard to debug because browsers block responses before your code runs. Reviewing Access-Control-Allow-Origin, Access-Control-Allow-Credentials, and Access-Control-Expose-Headers helps you confirm whether an API is truly accessible from a frontend origin. Combine this with the chosen method to mimic how your clients request data.

Practical Workflow Examples

1) Verifying a canonical redirect

Enter the non-canonical URL (for example, http:// or a non-www hostname), disable redirect following, and run a HEAD request. You should see a 301/308 status and a Location header pointing to the canonical destination. Then enable redirects to confirm the final hop returns 200 and that security and cache headers are present on the final response as well.

2) Diagnosing “it works in Chrome but not in Safari”

Set a Safari User-Agent and compare headers to a Chrome User-Agent. Differences in Vary, compression, or content-type can explain client-specific failures. If the response is device-dependent, this comparison is often faster than reproducing the issue on multiple devices.

3) Checking cookie attributes after a login change

After adjusting authentication, inspect Set-Cookie output. Ensure cookies include Secure on HTTPS sites, include HttpOnly where appropriate, and use the right SameSite mode. Incorrect cookie scope is a common cause of login loops, cross-subdomain session loss, and “works locally but not in production” surprises.

Why Choose This Tool

Unlike scattered browser screenshots or noisy logs, this HTTP Headers Viewer presents a clean, shareable summary of what a server actually returns at the HTTP layer. It’s ideal for developers and DevOps engineers who need quick confirmation of configuration changes, and for QA teams who want reproducible checks across staging and production.

With redirect-chain visibility, method selection, and a customizable User-Agent, you can inspect real-world delivery scenarios in seconds. Whether you’re tightening security headers, tuning cache lifetimes, or diagnosing a tricky login redirect, this tool helps you move from symptoms to evidence—fast.