Response headers carry the facts that decide how a page behaves: its content type, its caching policy, its security headers, and whether it redirected at all. When a page renders oddly, caches stubbornly, or refuses to embed, the headers usually explain why, but browsers hide them behind developer tools. This viewer surfaces them in one place. It fetches the URL from your browser and lists every response header it can read. Some servers block cross-origin reads, and this tool says so plainly instead of inventing headers: a blocked read is itself useful information about that server configuration.
Quick Answer: Enter a full URL and click Fetch Headers. Readable headers are listed; a blocked target gets an honest explanation instead.
Free Online Tool
HTTP Headers Viewer
Show response headers for a URL via the browser, with an honest fallback when the target blocks cross-origin reads.
How to Use the HTTP Headers Viewer
- Type or paste the full URL, including https://.
- Click Fetch Headers.
- Wait a moment while your browser requests the URL.
- Read the header list, one name and value per line.
- If the read is blocked, read the explanation and check the headers in your browser developer tools instead.
- Compare security and cache headers against the values you expect.
Key Features
- Lists every readable response header with its value.
- Shows the HTTP status code alongside the headers.
- Explains cross-origin blocks honestly instead of faking data.
- Handles redirects by reporting the final response.
- Works for any URL your browser can reach.
- No server in the middle: the request comes from your own browser.
What the Result Means
A listed header is a fact about the response your browser received. Missing security headers such as content-security-policy or strict-transport-security mean the server did not send them, which is a finding, not an error in this tool. A blocked result means the server did not grant this page permission to read its headers, which is normal for many sites and does not mean the site is down. For a blocked target, your browser developer tools Network tab shows the same headers because it runs with different permissions than a web page.
Worked Example
Imagine a page that keeps showing last week content after a deploy. Fetching its headers shows cache-control: max-age=86400, which tells the browser to reuse the page for a full day, and no cache-busting version on the asset URLs. That single header explains the stale content and points to the fix: shorten the max-age or version the assets. If instead the fetch is blocked with the CORS explanation, you learn the server sends no cross-origin permission, and you switch to the browser developer tools for the same headers.
Best Practices and Tips
- Check cache-control first when a changed page keeps showing old content.
- Look for x-content-type-options and frame-ancestors when embedding or security is in question.
- Compare headers between the www and bare-domain versions of a site; they often differ.
- A 301 or 302 status with a location header explains a redirect loop or surprise destination.
- Record the full header set when reporting a caching or security issue to a host.
Common Mistakes to Avoid
- Assuming a blocked read means the site is broken or offline.
- Reading only the status code and ignoring the headers that explain it.
- Trusting a cached response when debugging: headers from a cache differ from fresh ones.
- Expecting this page to read headers from servers that never granted it permission.
Frequently Asked Questions
Why are some sites blocked?
Browsers only let a page read response headers when the server sends CORS permission. Many sites do not, for good security reasons.
Does this tool send my URL to a server?
No. The request is made by your browser directly, and no proxy or logging server is involved.
Can I see request headers too?
No, this viewer shows response headers only. Request headers are visible in your browser developer tools.
What if the URL redirects?
The browser follows redirects automatically, so you see the final response headers, including its status code.