What Are HTTP Request Headers And How Can You Use Them When Web Scraping?

HTTP headers let the server and the client transfer additional information through an HTTP response or request. If you use web scraping to gather data for your business, you can optimize HTTP headers to decrease your API’s chances of getting banned by the target server. You can also use them to accelerate the process.

Table of Contents

Read this guide to learn more about HTTP headers and how to set them up. We’ve also included an HTTP request headers list to briefly explain the headers you’ll most likely need or run into.

What Are HTTP Headers?

An HTTP header is part of the Hypertext Transfer Protocol (HTTP). The header’s purpose is to transmit extra data between clients and the server through the response and request header. An HTTP header consists of a case-insensitive name followed by a colon and its value, such as content-length: 20166 and access-control-allow-credentials: true.

You can view HTTP headers in Internet Explorer by:

1. Launching IE’s built-in developer tools by pressing F12.
2. Opening the Network tool using Ctrl + 4.
3. Manually start data collection using F5.
4. Double-clicking on the name of each object to view the HTTP headers.

Types of HTTP Headers

Headers can be grouped in several ways.

First, they can be grouped according to their context:

• HTTP response header: These headers contain additional data about the fetched request by the client, such as the server providing it or its location.
• HTTP request header: HTTP request headers are sent by the client, the machine making the request, in an HTTP transaction. These headers (like http_accept) send a lot of information about the request’s source, such as the type and version of the application or browser used. This is the type of header you’ll need to be most familiar with to improve your web scraping endeavors.
• HTTP entity header: Entity headers contain data about the body of the resource, like content length and Multipurpose Internet Mail Extensions (MIME) type.
• General HTTP header: These headers apply to responses and requests. However, they don’t apply to the content.

You can also classify headers’ purposes according to how proxies handle them:

• TE: This request header shows the transfer encodings the user agent is willing to accept.
• Keep-Alive: The HTTP header Keep-Alive maintains a connection between the server and the client, reducing the time required to serve files.
• Connection: The HTTP header Connection controls whether the network connection stays open once the current transaction ends. If the value sent is keep-alive, the connection will not be closed. As a result, the header will allow subsequent requests to the same server to be made and done. Connection helps to receive and send multiple HTTP responses and requests using a single TCP connection.
• Proxy-Authenticate: This response header allows the proxy server to transfer the request further by authenticating it.
• Proxy-Authorization: This header has the credentials for authenticating a user agent to a proxy server.
• Trailer: This header lets the sender include additional fields at the end of chunked messages. Senders can use Trailer to supply potentially dynamically-generated metadata if needed, such as to provide information about the context of the data in the request.
• Upgrade: This header can only be used to upgrade a preestablished server and client connection to a different protocol. For instance, a client can upgrade a connection from HTTP or HTTPS to WebSocket.

Finally, you can divide headers according to the behavior or non-caching and caching proxies:

• Hop-by-hop headers: These headers are for one transport-level connection only. They are consumed and processed by the proxy currently handling the request, so they are not forwarded by proxies or stored by caches.
• End-to-end headers: These headers are only transmitted to the ultimate recipient of a response or request, which is the server for a request and the client for a response. Caches must store these headers, and intermediate proxies must retransmit them unmodified.

HTTP Request Headers List

HTTP header fields are lists of strings received and sent by the server and client on every HTTP request and response. Typically invisible to end-users, they are only logged or processed by the client and server applications.

Here are some common HTTP header examples.

Accept fields

Accept fields specify what kind of response the server accepts. The general syntax is:

Accept: <MIME_type>/<MIME_subtype) ;q=value

They include:

• Accept: This field tells the server what kind of data can be returned.
• Accept-Charset: You can use this field in HTTP headers to state which character sets the client accepts for the response. If there are several character sets, you can enter them separated by commas.
• Accept-Encoding: This header field limits the acceptable encoding algorithms for the response.
• Accept-Language: This field informs the server what human-readable language the server will probably return.

Authorization

This field verifies a user agent with the server. The syntax is:

Authorization: <type> <credentials>

Host

The Host field specifies the port number and internet host for the requested resource. The syntax is:

Host: host:port

If there is no port number, the field will use the default port of 80.

Referer

This field allows the client to specify the URL of the resource from which the URL was requested. The syntax is:

Referer: URL

User-Agent

The User-Agent field sends client data to a server. The syntax is:

User-Agent: <product>/<product version> <comment>

How To Set HTTP Headers

You can set HTTP headers by opening your integrated development environment (IDE) and importing and using the HTTP headers you want.

For instance, suppose you want to set several User-Agents to fool anti-scraping tools into thinking you’re more than one scraper. You can copy the User-Agents you want from this list and add them to your scraper in your IDE.

How HTTP Headers Can Help Web Scraping

You can use HTTP headers to accelerate and streamline web scraping — collecting data from the web. If you’re using an API over a prebuilt scraper like Scraping Robot, you’ll need request headers like the ones mentioned above. These provide more information to the server processing your request and can help you gather data faster.

Minimize chances of getting banned by target servers

Most modern web administrators know they will probably get their data scraped by competitors who want to understand how their business works. As such, they use tools to automatically ban suspicious user requests, such as multiple user requests coming from the same IP address. Some web servers may even show incorrect information when detecting suspicious user agents.

Fortunately, you can use HTTP headers to minimize the chances of getting banned. For instance, you can manipulate and create different User-Agent header strings to make it seem like you are multiple organic users instead of a web scraper. Specifically, you can assign each “user” different browsers to make it look like the requests are coming from different browsers on different computers. Example: One user uses Mozilla Firefox on macOS Catalina 10.15.4, while another uses Chrome on Microsoft Windows 10.

Similarly, you can use the Referer request header — which shows what website the user was on before going to the target site — to minimize the chances of getting blocked. Websites often block users that directly go to their site since they are more likely to be bots. Accordingly, you can make your web scraper seem more human by pointing the Referer header to a random site, such as https://www.google.com.

Increase web scraping speed

You can also use HTTP headers to increase web scraping speed.

For example, the Accept-Encoding header can tell the web server which compression algorithm to use when handling the request. This allows you to compress information sent from the web server to the client, leading to less lag and an increased scraping rate.

Accelerate Your Scraping With Scraping Robot

HTTP headers can minimize web scrapers’ chances of getting blocked by target servers and increase web scraping speed. However, they can be a lot of work, especially when you only have a few weeks or days to scrape hundreds or thousands of sites.

Fortunately, Scraping Robot is here to help. Reliable and powerful, Scraping Robot is a prebuilt scraper that handles every part of the scraping process for you, including rotating and managing proxies, CAPTCHA solving, browser scalability, and metadata parsing. We can also help you identify and stay on top of anti-scraping updates from target websites.

Interested in experiencing the Scraping Robot difference? Sign up today to get 5,000 scrapes per month for free. If you want more, you can join our Business or Enterprise tiers, which offer up to or over 500,000 scrapes per month.

The information contained within this article, including information posted by official staff, guest-submitted material, message board postings, or other third-party material is presented solely for the purposes of education and furtherance of the knowledge of the reader. All trademarks used in this publication are hereby acknowledged as the property of their respective owners.

Scraping Robot