How to Implement User Agent Rotation for Web Scraping

Posted by Vlad Mishkin | October 2, 2023 | Tags: Programming | Python |

Web scraping is a powerful tool for acquiring valuable data from the internet. However, it often entails overcoming obstacles like bot detection and IP blocking. One possible solution to these challenges is user agent rotation. This blog post will explore the importance of user agents in web scraping, the need for rotating user agents, and various techniques to implement user agent rotation in Python. Get ready to enhance your web scraping skills and unlock new possibilities with user agent rotation for web scraping!

Key Takeaways

  • Understanding user agents and their strings are essential for successful web scraping.
  • Rotating user agents is important to protect against blocks and detection, which can be done using WebScraping.AI API, Python libraries/tools, Scrapy middleware & Selenium for browser automation.
  • Keeping user agent strings up-to-date with random intervals between requests helps reduce the risk of being blocked or detected.

Understanding User Agents in Web Scraping

User agents are instrumental in web scraping as they assist servers in recognizing browser types, devices, and operating systems to ensure compatibility. A user agent is a unique identifier sent to web servers that provides information about the browser and operating system utilized by the user.

Using a valid browser user agent is a prerequisite when leveraging web scraping tools, to prevent websites from blocking requests. Utilizing the optimal scraping user agent reduces the chances of being blocked.

User Agent Strings

User agent strings are unique identifiers sent to web servers, providing information about the browser and operating system. They typically include comment components such as platform or release version, for example, “Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/ Safari/537.36” (Google Chrome on MacOS desktop).

A User Agent string is typically broken down into five main components:

1. Browser/Browser Version: This is the web browser that the client is using to access the web server (e.g. Chrome, Firefox, Safari, Edge). The browser version often follows this component.

2. Rendering Engine: This is the software component used by a web browser to transform the web content (like HTML, CSS, JavaScript) into a visual representation. Examples include Gecko for Firefox; Blink for Chrome.

3. Operating System/ OS Version: This is the operating system that the client is running on their computer (e.g. Windows, MacOS, Linux). The OS version often follows this component.

4. Device Type: For mobile devices, the User Agent string often contains the specific model of the device (e.g. iPhone, iPad, Android).

5. Bot/Crawler indication: For bots or web crawlers (like Googlebot, Bingbot), this will be stated in the string.

The structure of User Agent strings is different for different browsers, which can make them somewhat difficult to parse. They also may contain other details such as the architecture of the CPU, language preference, and more.

The Purpose of User Agent

Each specific browser or application sends the user agent string to websites on every visit. It is a unique identifier that denotes the:

  • Application
  • Operating system
  • Software vendor
  • Software version

Responsible for making an HTTP request to a web server.

A thorough understanding of the role of requesting software user agents in web scraping allows you to configure your web scraper to emulate real browsers, thereby avoiding any unwarranted attention from anti-bot systems.

The Need for Rotating User Agents

In web scraping, rotating user agents is a key strategy to evade detection and blocking by anti-bot systems, and to safeguard IP addresses. User agent rotation is the process of alternating user agents while making web requests, to access more data and increase scraper efficiency.

A rotating proxies API, such as WebScraping.AI can set up automatic IP rotation and user agent string rotation, allowing requests to appear as if they originated from different web browsers.

Bypassing Bot Detection

Bypassing bot detection involves using a variety of techniques, such as:

  • Using different user agents to mimic real browsers
  • Using different headers
  • Rotating IP addresses to avoid detection
  • Randomizing request intervals to simulate human behavior
  • Utilizing CAPTCHA solving services to bypass security measures

Bot detection is the process of identifying and distinguishing between automated bots and human users by analyzing web traffic and identifying patterns that indicate human behavior or automated bots.

To bypass bot detection, you can:

  • Use a variety of user agents and headers to imitate real browsers and prevent triggering anti-scraping measures
  • Rotate user agents
  • Preserve IP addresses
  • Keep user agents up-to-date

Following these strategies can improve your chances of bypassing bot detection.

Implementing User Agent Rotation with Python

Implementing user agent rotation with Python involves creating a list of user agents, randomly selecting one, and setting it as the header for requests. This process allows your web scraper to emulate a variety of browsers and devices, making it more difficult for websites to detect and block your scraping efforts.

Mastering user agent rotation in Python empowers you to optimize your web scraping projects, thereby facilitating easy access to valuable data.

Creating a List of User Agents

Creating a list of user agents involves gathering a variety of browser user agent strings to use in rotation. In order to create a list of user agents in Python, one can obtain a list of user agent strings from actual browsers. There are multiple sources available online, but usually the best way to go is to use pre-processed lists published as libraries, here are some examples:

Once obtained, this list can be stored in a Python list or any other fitting data structure for future use in web scraping or HTTP requests. The list of user agents can be leveraged to cycle through different user agents when making requests to a website, facilitating the avoidance of bot detection and maintaining your IP address.

Randomly Selecting a User Agent

Randomly selecting a user agent from the list helps to make requests look more organic and less likely to be identified as bot activity. When randomly selecting a user agent from a list in Python, libraries or tools such as ‘random-user-agent’, ‘fake_useragent’, or online tools like ‘’ provide a collection of user agents from which a random one can be generated.

For effective user agent rotation, it is advisable to keep user agents current, maintain random intervals between requests, and align headers with user agents.

Setting the User Agent Header

Setting the user agent header involves adding the chosen user agent string to the request headers before making the request. This modification helps the request appear more organic and less prone to being identified as bot activity.

In order to set the user agent header, one must add the chosen user agent string to the request headers prior to making the request. Correctly setting the user agent header enables your web scraper to better imitate real browsers, thereby reducing the risk of detection and blocking.

Here is a code example in Python:

import requests
from fake_useragent import UserAgent
from itertools import cycle

# Initialize UserAgent
ua = UserAgent()

# Create a list of user_agents
user_agents = [,, ua['google chrome'], ua.firefox, ua.ff, ua.safari,, ua.opera, ua.phantom]

# Create a cycle of user agents
user_agents_cycle = cycle(user_agents)

# Make a request with different user agents
for _ in range(10):
    # Get the next user agent in the cycle
    user_agent = next(user_agents_cycle)
    # Set the headers
    headers = {
        'User-Agent': user_agent,
    # Make the request
    response = requests.get('', headers=headers)
    # Print the response

Advanced User Agent Rotation Techniques

Advanced user agent rotation techniques include using Scrapy middleware for rotating user agents and Selenium for browser automation. These advanced techniques provide additional layers of protection against bot detection and IP blocking, allowing your web scraper to access even more data without being detected.

Mastering these advanced user agent rotation techniques allows you to augment your web scraping capabilities and explore new opportunities.

Rotating User Agents in Scrapy

Rotating user agents in Scrapy involves using middleware to automatically select and set user agents for each request. By integrating user agent rotation into the Scrapy framework, you can improve your web scraper’s efficiency and reduce the chances of detection and blocking.

Optimizing user agent rotation in Scrapy can be achieved by ensuring user agents are current, requests are made at random intervals, and headers are aligned with user agents.

Rotating User Agents with Selenium

Rotating user agents with Selenium allows for more advanced browser automation and interaction, further reducing the likelihood of detection. Selenium can be employed to rotate user agents by randomly selecting a user agent from a list of user agents and setting the user agent header.

Utilizing user agent rotation with Selenium provides a more comprehensive browser automation and interaction, thereby decreasing the probability of detection.

Tips for Effective User Agent Rotation

To enhance the efficacy of your user agent rotation, consider these useful tips. Keeping user agents up-to-date, maintaining random intervals between requests, and matching headers with user agents are all essential strategies for successful user agent rotation.

Adhering to these tips and incorporating user agent rotation in your web scraping projects will help you circumvent detection, maintain IP addresses, and effortlessly access valuable data.

Keeping User Agents Up-to-date

Keeping user agents up-to-date ensures that the scraper emulates current browser versions, reducing the risk of detection and blocking. Regularly updating your list of user agents will help maintain the effectiveness of your user agent rotation strategy.

Maintaining Random Intervals Between Requests

Maintaining random intervals between requests helps avoid triggering rate limits and anti-bot measures. By spacing out your requests randomly, your web scraper will appear more like a human user, thus reducing the likelihood of detection.

Matching Headers with User Agents

Matching headers with user agents ensures that the entire request appears consistent and legitimate, further reducing the risk of detection. To match headers with user agents, it is necessary to set the User-Agent request header to a specific value that identifies the application or device making the HTTP request.


In conclusion, user agent rotation is a powerful technique for enhancing your web scraping projects. By understanding the role of user agents, implementing user agent rotation in Python, and employing advanced techniques like Scrapy middleware and Selenium, you can avoid detection, preserve IP addresses, and access valuable data with ease. Embrace the power of user agent rotation and unlock new possibilities in your web scraping endeavors!

Frequently Asked Questions

What is user agent in web scraping?

User Agents are strings sent to the server as part of the request headers, allowing web scraping programs to identify themselves and the software they're running on. This helps websites distinguish between automated requests and actual human visitors.

How do I get a user agent for web scraping?

To get a user agent for web scraping, copy the user string of a real browser (Mozilla, Chrome, Edge, Opera, etc.) and paste it in a dict with the key 'user-agent' when using Python request. This will ensure that the web scraping is done in a way that is indistinguishable from a real browser.

What is the workflow of web scraping?

The workflow of web scraping typically involves sending a request to the website URL, loading the HTML code, applying scraping technologies to extract and transform the data, and finally storing it in a structured format. A more advanced scraper might even extract all the CSS and Javascript elements as well.

Why is it important to rotate user agents?

Rotating user agents is important as it helps to avoid detection and blocking by anti-bot systems, allowing IP addresses to remain safe.

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