HTTP Header Parser: Analyze Request and Response Headers Online
Paste raw HTTP request or response headers and instantly parse them into a clean key-value table for easy inspection and debugging.
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HTTP headers carry critical metadata in every web request and response — caching directives, content types, authentication tokens, security policies, and more. When debugging a web application or API integration, reading raw HTTP headers is often necessary, but a wall of unformatted header text can be hard to scan quickly.
This HTTP header parser takes raw header text — copied from browser DevTools, a proxy tool like Charles or Fiddler, curl output, or a server log — and structures it into a clean, readable table of key-value pairs. It handles request headers, response headers, and the status line, making it easy to find the header you're looking for without scanning a long string manually.
Whether you're auditing security headers, troubleshooting a CORS error, inspecting cache-control directives, or checking what a server is returning, this tool gives you an instant, organized view of the raw HTTP header data.
What Are HTTP Headers?
HTTP headers are key-value pairs sent at the beginning of every HTTP request and response. They provide metadata about the message: its content type, length, encoding, caching instructions, authentication credentials, cookies, and much more.
Request headers are sent by the client (browser, application, or cURL) to tell the server about the request. Common request headers include `Content-Type`, `Authorization`, `Accept`, `User-Agent`, and `Cookie`.
Response headers are sent by the server back to the client. They include `Content-Type`, `Cache-Control`, `Set-Cookie`, `Location` (for redirects), security headers like `Content-Security-Policy`, and many others. Headers follow the format `Header-Name: value`, one per line, with the status line at the top of a response.
How to Use This Tool
Paste any raw HTTP headers and get an instant structured breakdown.
- 1
Copy raw headers
Get raw HTTP headers from browser DevTools (Network tab > click a request > Headers > view source), curl verbose output (-v flag), a proxy tool, or a server log.
- 2
Paste into the input field
Paste the raw header block including the status line (if present) into the text area. The tool accepts both request and response header formats.
- 3
Click Parse
The tool splits the input on newlines, identifies the status line, and separates each header into its name and value.
- 4
Browse the table
Review the parsed headers in the output table. Each row shows the header name and its full value, making it easy to find specific headers.
- 5
Search or filter
Use the search box to filter headers by name — useful when a response contains many headers and you need to find a specific one quickly.
Common Use Cases
HTTP header analysis is a core part of web debugging and security work.
- Debugging CORS errors — checking the `Access-Control-Allow-Origin` and related response headers to understand why cross-origin requests are being blocked.
- Auditing security headers — verifying that headers like `Content-Security-Policy`, `X-Frame-Options`, `Strict-Transport-Security`, and `X-Content-Type-Options` are present and correctly configured.
- Troubleshooting caching issues — reading `Cache-Control`, `Expires`, `ETag`, and `Last-Modified` headers to understand why content is or isn't being cached.
- Inspecting authentication flows — examining `Authorization`, `WWW-Authenticate`, and `Set-Cookie` headers during login and session debugging.
- Reviewing API responses — understanding what content type, encoding, and rate-limit headers an API is returning alongside its response body.
Tips and Best Practices
Use these tips to make the most of HTTP header analysis.
- In Chrome DevTools, click 'view source' under the Headers tab to see raw headers exactly as sent, without the browser's parsed view.
- Run `curl -I` to fetch only response headers from a URL without downloading the response body — useful for quick header checks.
- Check for duplicate headers — some configurations accidentally send the same header twice (e.g., `Content-Type`), which can cause unexpected behavior.
- Security headers should be verified in production, not just development — staging environments often have different reverse proxy configurations.
- When debugging `Set-Cookie` headers, look at the `Path`, `Domain`, `Secure`, `HttpOnly`, and `SameSite` attributes alongside the cookie value.
Frequently Asked Questions
What is the difference between request and response headers?
Request headers are sent by the client to provide context about the request — such as the content type being sent, accepted response types, or authentication credentials. Response headers are sent by the server to describe the response — such as the content type returned, caching rules, and cookies to set.
What is a CORS header and why does it matter?
CORS (Cross-Origin Resource Sharing) headers like `Access-Control-Allow-Origin` tell browsers whether a web page from one origin is permitted to read responses from a different origin. Without proper CORS headers, browsers block cross-origin API calls for security reasons.
What does the Content-Type header do?
The `Content-Type` header tells the recipient what format the body of the message is in — for example, `application/json`, `text/html`, or `multipart/form-data`. Both requests and responses include a Content-Type when they have a body.
What is the Strict-Transport-Security header?
HSTS (HTTP Strict Transport Security) instructs browsers to only communicate with the server over HTTPS, even if the user types a plain HTTP URL. It prevents protocol downgrade attacks and cookie hijacking.
Why might a header have multiple values?
Some headers accept multiple values separated by commas (e.g., `Accept: text/html, application/json`). Others, like `Set-Cookie`, appear as multiple separate header lines — one per cookie. The HTTP specification defines how each header handles multiple values.
What does the ETag header do?
An `ETag` (entity tag) is a unique identifier assigned to a specific version of a resource. Clients store it and send it back in an `If-None-Match` header on subsequent requests. If the resource hasn't changed, the server returns 304 Not Modified instead of the full response, saving bandwidth.
Can I see HTTP/2 headers with this tool?
Yes. HTTP/2 headers carry the same semantic information as HTTP/1.1 headers and can be copied from browser DevTools or tools like Wireshark in the same key-value format. Note that HTTP/2 pseudo-headers like `:method` and `:path` may appear alongside regular headers.
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