How to Set Custom User-Agent Headers

Table Of Contents

• Problem
• Solution
• Explanation

Problem

You need to set a custom User-Agent header to identify your application, bypass default blocking, or comply with API requirements that check User-Agent strings.

Solution

// Basic User-Agent with fetch()
async function fetchWithUserAgent(url) {
  const response = await fetch(url, {
    headers: {
      'User-Agent': 'MyApp/1.0.0 (Node.js)'
    }
  });
  
  return await response.json();
}

// Browser-like User-Agent
async function fetchWithBrowserUA(url) {
  const response = await fetch(url, {
    headers: {
      'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36'
    }
  });
  
  return await response.json();
}

// Dynamic User-Agent
function createUserAgent(appName, version) {
  return `${appName}/${version} (Node.js ${process.version})`;
}

async function fetchWithDynamicUA(url, appName = 'MyBot', version = '1.0') {
  const userAgent = createUserAgent(appName, version);
  
  const response = await fetch(url, {
    headers: {
      'User-Agent': userAgent
    }
  });
  
  console.log('Using User-Agent:', userAgent);
  return await response.json();
}

// Axios with User-Agent
const axios = require('axios');

const client = axios.create({
  headers: {
    'User-Agent': 'MyAPI-Client/2.1.0'
  }
});

async function axiosWithUA(url) {
  const response = await client.get(url);
  return response.data;
}

Explanation

Set User-Agent in the headers object when making requests. Use descriptive names like AppName/Version (Platform) format for identification.

Some APIs require specific User-Agent strings or block requests without them. Browser-like User-Agents help avoid blocking, but always respect robots.txt and terms of service when scraping.