HEAD Request Method Explained

Introduction

The HEAD method is a lightweight HTTP request method used to retrieve the headers of a resource without downloading the body. It behaves exactly like a GET request but does not return the response content.

HEAD is extremely useful for checking resource availability, file size, caching rules, content type, and server metadata—without consuming unnecessary bandwidth.

This method powers many behind-the-scenes optimizations in browsers, CDNs, SEO crawlers, and download managers.

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What Is a HEAD Request?

A HEAD request asks the server to send only the headers of a resource, not the body.

Key Characteristics

• Same response headers as GET
• No response body
• Faster and bandwidth-efficient
• Safe and idempotent
• Commonly used to check if a resource exists

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Why HEAD Is Important

HEAD is essential for tasks like:

• Checking if a webpage exists before making a full GET
• Validating download size before downloading
• Verifying last modification date
• Checking content type (HTML, JSON, PDF, image, etc.)
• SEO bots verifying link validity
• Caching systems confirming freshness
• Monitoring server uptime

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When Should You Use HEAD?

Use HEAD when you need information about a resource without needing the resource itself.

Examples:

• Checking if an image URL is valid before rendering
• Checking if an API endpoint is reachable
• Determining file size before downloading
• Testing if a link is broken
• Verifying server metadata without heavy GET operations

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How HEAD Works Internally

1. Client sends HTTP HEAD request to a resource URL
2. Server processes it like a GET request
3. Server returns only headers
4. No body content is included
5. Client uses headers for decision-making

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Example 1: JavaScript Fetch API (HEAD Request)

fetch("https://example.com/image.jpg", { method: "HEAD" })
  .then(res => {
    console.log("Status:", res.status);
    console.log("Content-Length:", res.headers.get("Content-Length"));
    console.log("Content-Type:", res.headers.get("Content-Type"));
  })
  .catch(err => console.error(err));

Explanation

• Content-Length tells file size
• Content-Type tells what kind of resource it is
• Status tells whether the resource exists (200, 404, etc.)

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Example 2: HEAD with cURL

curl -I https://example.com

Common Output

HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8
Content-Length: 24890
Last-Modified: Wed, 20 Nov 2025 10:00:00 GMT

curl -I stands for “show headers only.”

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Example 3: HEAD Endpoint in Express.js (Node.js)

app.head("/api/check", (req, res) => {
  res.set({
    "X-Server-Status": "Running",
    "X-Version": "1.0.2"
  });
  res.status(200).end();
});

Explanation

• Sets custom headers
• No body is returned

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HEAD vs GET

Feature	HEAD	GET
Body Returned	❌ No	✔ Yes
Resource Loading	Fast	Complete
Primary Use	Metadata check	Full resource access
Network Cost	Very low	High
Idempotent	Yes	Yes

HEAD is perfect when you want to check something without downloading it.

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Common Response Codes for HEAD

Code	Meaning
200 OK	Resource exists
301/302 Redirect	Resource moved
404 Not Found	Resource missing
500 Server Error	Server failed to process

HEAD typically mirrors statuses of GET.

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Advantages of HEAD

• Saves bandwidth
• Faster response
• Perfect for link checking
• Useful for caching
• Good for SEO and monitoring

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Disadvantages of HEAD

• Limited functionality
• Not all servers handle HEAD correctly
• Some APIs do not implement HEAD explicitly

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Real-World Use Cases

1. Checking if a file exists before downloading

A download manager uses HEAD to show file size.

2. SEO link validators

Google-like bots verify pages exist without loading the content.

3. CDN cache checks

Cloudflare, Akamai, etc., rely on HEAD to determine resource freshness.

4. Website uptime checks

Monitoring tools perform HEAD ping checks.