Node-Fetch - Setting Fake User-Agents

Node-Fetch: Setting Fake User-Agents

Using Fake User-Agents With NodeJs Node-Fetch Library

To use fake user-agents with Node-Fetch, you just need to define a user-agent in a headers object and pass it into the headers attribute in your request options.

import fetch from 'node-fetch';

(async () => {
    const url = 'http://httpbin.org/headers'
    const options = {
      method: 'GET',
      headers: {
        'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.111 Safari/537.36'
      }
    }

    try{
        const response = await fetch(url, options)
        const data = await response.json()
        console.log(data);

    } catch (error){
        console.log('error', error)
    }
    
})();

One of the most common reasons for getting blocked whilst web scraping is using bad user-agents.

However, integrating fake user-agents into your NodeJs web scrapers that use Node-Fetch is very easy.

So in this guide, we will go through:

What Are Fake User-Agents?
How To Set A User Agent In NodeJs Node-Fetch
How To Rotate User-Agents
How To Manage Thousands of Fake User-Agents
Why Use Fake Browser Headers
ScrapeOps Fake Browser Headers API

First, let's quickly go over some the very basics.

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What Are Fake User-Agents?

User Agents are strings that let the website you are scraping identify the application, operating system (OSX/Windows/Linux), browser (Chrome/Firefox/Internet Explorer), etc. of the user sending a request to their website. They are sent to the server as part of the request headers.

Here is an example User agent sent when you visit a website with a Chrome browser:

'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.82 Safari/537.36'

When scraping a website, you also need to set user-agents on every request as otherwise the website may block your requests because it knows you aren't a real user.

In the case of [Node-Fetch]((https://github.com/node-fetch/node-fetch), when you send a request by default it doesn't include a User-Agent. This will clearly identify that the request isn't being made with a real browser.

'User-Agent': '',

This user-agent will clearly identify your requests as suspicious, so the website can easily block you from scraping the site.

That is why we need to manage the user-agents we use with Node-Fetch when we send requests.

How To Set A Fake User-Agent In NodeJs Node-Fetch

Setting Node-Fetch to use a fake user-agent is very easy. You just need to define a user-agent in a headers object and pass it into the headers attribute in your fetch options.

import fetch from 'node-fetch';

(async () => {
    const url = 'http://httpbin.org/headers'
    const options = {
      method: 'GET',
      headers: {
        'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.111 Safari/537.36'
      }
    }

    try{
        const response = await fetch(url, options)
        const data = await response.json()
        console.log(data);

    } catch (error){
        console.log('error', error)
    }
    
})();

From here Node-Fetch will use the above user-agent to make the request. All request headers, including User-Agent, are reflected in response JSON, which is loaded with response.json method.

How To Rotate User-Agents

Rotating through user-agents is also pretty straightforward when using NodeJS Node-Fetch library. We just need a list of user-agents in our scraper and use a random one with every request.

import fetch from 'node-fetch';
import randomUserAgent from 'random-useragent';

const userAgents = [
  'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.82 Safari/537.36',
  'Mozilla/5.0 (iPhone; CPU iPhone OS 14_4_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.3 Mobile/15E148 Safari/604.1',
  'Mozilla/4.0 (compatible; MSIE 9.0; Windows NT 6.1)',
  'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36 Edg/87.0.664.75',
  'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 Edge/18.18363'
];

const url = 'http://httpbin.org/headers'

const headers = {
  'User-Agent': randomUserAgent.getRandom(userAgents)
};

const options = {
  method: 'GET',
  headers: headers
};

fetch(url, options)
  .then(async response => {
    console.log(await response.json());
  })
  .catch(error => {
    console.error(error);
  });

This works but it has drawbacks as we would need to build & keep an up-to-date list of user-agents ourselves.

How To Manage Thousands of Fake User-Agents

A better approach would be to use a free user-agent API like ScrapeOps Fake User-Agent API to download an up-to-date user-agent list when your scraper starts up and then pick a random user-agent for each request.

To use the ScrapeOps Fake User-Agents API you just need to send a request to the API endpoint to retrieve a list of user-agents.

http://headers.scrapeops.io/v1/user-agents?api_key=YOUR_API_KEY

To use the ScrapeOps Fake User-Agent API, you first need an API key which you can get by signing up for a free account here.

Example response from the API:

{
  "result": [
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.5 Safari/605.1.15",
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.53 Safari/537.36",
    "Mozilla/5.0 (Windows NT 10.0; Windows; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.114 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/603.3.8 (KHTML, like Gecko) Version/10.1.2 Safari/603.3.8",
    "Mozilla/5.0 (Windows NT 10.0; Windows; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.114 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0 Safari/605.1.15",
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.53 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0 Safari/605.1.15",
    "Mozilla/5.0 (Windows NT 10.0; Windows; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.114 Safari/537.36",
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.53 Safari/537.36"
  ]
}

To integrate the Fake User-Agent API you should configure your scraper to retrieve a batch of the most up-to-date user-agents when the scraper starts and then configure your scraper to pick a random user-agent from this list for each request.

Here is an example NodeJs Node-Fetch scraper integration:

import fetch from 'node-fetch';

const SCRAPEOPS_API_KEY = '9a90a1dd-2575-4f18-8646-139b2d7de711';
const url = `http://headers.scrapeops.io/v1/user-agents?api_key=${SCRAPEOPS_API_KEY}`

async function getUserAgentList() {
  const response = await fetch(url);
  const data = await response.json()
  return data.result || [];
}

function getRandomUserAgent(userAgentList) {
  const randomIndex = Math.floor(Math.random() * userAgentList.length);
  return userAgentList[randomIndex];
}

const urlList = [
  'https://jsonplaceholder.typicode.com/posts/1',
  'https://jsonplaceholder.typicode.com/posts/2',
  'https://jsonplaceholder.typicode.com/posts/3'
];

(async () => {
  try {
    const userAgentList = await getUserAgentList();

    for (const url of urlList) {
      const headers = {
        'User-Agent': getRandomUserAgent(userAgentList)
      };

      const options = {
        headers: headers
      };

      const response = await fetch(url, options);
      const data = await response.json()
      console.log(data);
    }
  } catch (error) {
    console.error(error);
  }
})();

Here the scraper will use a random user-agent for each request.

Why Use Fake Browser Headers

For simple websites, simply setting an up-to-date user-agent should allow you to scrape a website pretty reliably.

However, a lot of popular websites are increasingly using sophisticated anti-bot technologies to try and prevent developer from scraping data from their websites.

These anti-bot solutions not only look at your requests user-agent when analysing the request, but also the other headers a real browser normally sends.

By using a full set of browser headers you make your requests look more like real user requests, and as a result harder to detect.

Here are example headers when using a Chrome browser on a MacOS machine:

sec-ch-ua: " Not A;Brand";v="99", "Chromium";v="99", "Google Chrome";v="99"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "macOS"
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.83 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: none
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Accept-Encoding: gzip, deflate, br
Accept-Language: en-GB,en-US;q=0.9,en;q=0.8

As we can see, real browsers don't just send User-Agent strings but also a number of other headers that are used to identify and customize the request.

So to improve the reliability of our scrapers we should also include these headers when making requests.

You could build a list of fake browser headers yourself, or you could use the ScrapeOps Fake Browser Headers API to get an up-to-date list every time your scraper starts up.

ScrapeOps Fake Browser Headers API

The ScrapeOps Fake Browser Headers API is a free API that returns a list of optimized fake browser headers that you can use in your web scrapers to avoid blocks/bans and improve the reliability of your scrapers.

API Endpoint:

http://headers.scrapeops.io/v1/browser-headers?api_key=YOUR_API_KEY

Response:

{
  "result": [
    {
        "upgrade-insecure-requests": "1",
        "user-agent": "Mozilla/5.0 (Windows NT 10.0; Windows; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.114 Safari/537.36",
        "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9",
        "sec-ch-ua": "\".Not/A)Brand\";v=\"99\", \"Google Chrome\";v=\"103\", \"Chromium\";v=\"103\"",
        "sec-ch-ua-mobile": "?0",
        "sec-ch-ua-platform": "\"Windows\"",
        "sec-fetch-site": "none",
        "sec-fetch-mod": "",
        "sec-fetch-user": "?1",
        "accept-encoding": "gzip, deflate, br",
        "accept-language": "bg-BG,bg;q=0.9,en-US;q=0.8,en;q=0.7"
    },
    {
        "upgrade-insecure-requests": "1",
        "user-agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.53 Safari/537.36",
        "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9",
        "sec-ch-ua": "\".Not/A)Brand\";v=\"99\", \"Google Chrome\";v=\"103\", \"Chromium\";v=\"103\"",
        "sec-ch-ua-mobile": "?0",
        "sec-ch-ua-platform": "\"Linux\"",
        "sec-fetch-site": "none",
        "sec-fetch-mod": "",
        "sec-fetch-user": "?1",
        "accept-encoding": "gzip, deflate, br",
        "accept-language": "fr-CH,fr;q=0.9,en-US;q=0.8,en;q=0.7"
    }
  ]
}

To use the ScrapeOps Fake Browser Headers API, you first need an API key which you can get by signing up for a free account here.

To integrate the Fake Browser Headers API you should configure your scraper to retrieve a batch of the most up-to-date headers when the scraper starts and then configure your scraper to pick a random header from this list for each request.

Here is an example NodeJs Node-Fetch scraper integration:

import fetch from 'node-fetch';

const SCRAPEOPS_API_KEY = 'YOUR_API_KEY';
const url = `http://headers.scrapeops.io/v1/browser-headers?api_key=${SCRAPEOPS_API_KEY}`

async function getHeadersList() {
  const response = await fetch(url);
  const data = await response.json()
  return data.result || [];
}

function getRandomHeader(headerList) {
  const randomIndex = Math.floor(Math.random() * headerList.length);
  return headerList[randomIndex];
}

const urlList = [
  'https://jsonplaceholder.typicode.com/posts/1',
  'https://jsonplaceholder.typicode.com/posts/2',
  'https://jsonplaceholder.typicode.com/posts/3'
];

(async () => {
  try {
    const headerList = await getHeadersList();
    for (const url of urlList) {
      const headers = getRandomHeader(headerList);

      const options = {
        headers: headers
      };
      const response = await fetch(url, options);
      const data = await response.json()
      console.log(data);
    }
  } catch (error) {
    console.error(error);
  }
})();

For more information on check out the Fake Browser Headers API documenation.

Node-Fetch: Setting Fake User-Agents

Need help scraping the web?

What Are Fake User-Agents?​

How To Set A Fake User-Agent In NodeJs Node-Fetch​

How To Rotate User-Agents​

How To Manage Thousands of Fake User-Agents​

Why Use Fake Browser Headers​

ScrapeOps Fake Browser Headers API​

More Web Scraping Tutorials​