How to Configure Axios Proxy Authorization Headers

This article provides a complete guide on how to configure proxy authentication in the Axios HTTP client when operating behind corporate proxies. You will learn how to use Axios's built-in proxy configuration, how to handle HTTPS traffic using dedicated proxy agents like https-proxy-agent, and how to manually construct custom Proxy-Authorization headers for complex network environments.

1. Using Built-in Axios Proxy Settings

For standard HTTP proxy requests, Axios provides a native proxy configuration object. When you supply the auth property containing a username and password, Axios automatically encodes the credentials in Base64 and attaches the Proxy-Authorization: Basic <base64-credentials> header to the request.

const axios = require('axios');

axios.get('http://example.com/api/data', {
  proxy: {
    protocol: 'http',
    host: 'proxy.corporate.local',
    port: 8080,
    auth: {
      username: 'corporate_user',
      password: 'corporate_password'
    }
  }
})
.then(response => console.log(response.data))
.catch(error => console.error('Request failed:', error.message));

2. Handling HTTPS Corporate Proxies with `https-proxy-agent`

The native Axios proxy object often fails when tunneling requests over HTTPS because of how the Node.js HTTP runtime handles the CONNECT method. To reliably pass proxy authentication over HTTPS in a corporate environment, use the https-proxy-agent library.

Installation

npm install https-proxy-agent

Implementation

Include the authentication credentials directly in the proxy connection URL, and pass the agent to Axios via the httpsAgent config option:

const axios = require('axios');
const { HttpsProxyAgent } = require('https-proxy-agent');

const proxyHost = 'proxy.corporate.local';
const proxyPort = 8080;
const username = encodeURIComponent('corporate_user');
const password = encodeURIComponent('corporate_password');

// Construct the proxy URL with credentials
const proxyUrl = `http://${username}:${password}@${proxyHost}:${proxyPort}`;

const httpsAgent = new HttpsProxyAgent(proxyUrl);

const client = axios.create({
  httpsAgent,
  proxy: false // Disables Axios's default proxy handling
});

client.get('https://api.external-service.com/data')
  .then(response => console.log(response.data))
  .catch(error => console.error('HTTPS Proxy Request Failed:', error.message));

3. Manually Setting the Proxy-Authorization Header

If your corporate proxy requires custom headers or token-based proxy authentication (such as Bearer or NTLM tokens), you can manually compute and inject the header into the agent configuration or request headers.

Basic Authentication Example

const axios = require('axios');
const { HttpsProxyAgent } = require('https-proxy-agent');

const username = 'corporate_user';
const password = 'corporate_password';
const base64Auth = Buffer.from(`${username}:${password}`).toString('base64');

const httpsAgent = new HttpsProxyAgent('http://proxy.corporate.local:8080', {
  headers: {
    'Proxy-Authorization': `Basic ${base64Auth}`
  }
});

axios.get('https://api.external-service.com/data', {
  httpsAgent,
  proxy: false
})
.then(response => console.log(response.data))
.catch(error => console.error(error.message));

4. Corporate Environment Considerations

SSL/TLS Inspection: Corporate proxies often perform SSL inspection using custom Certificate Authorities (CAs). If you encounter UNABLE_TO_VERIFY_LEAF_SIGNATURE or SELF_SIGNED_CERT_IN_CHAIN errors, provide the corporate root certificate via the agent:
```
const fs = require('fs');
const httpsAgent = new HttpsProxyAgent('http://user:pass@proxy:8080', {
  ca: fs.readFileSync('/path/to/corporate-ca.pem')
});
```
Special Characters in Passwords: Always use encodeURIComponent() on your username and password when formatting proxy connection strings to prevent URL parsing errors.
Environment Variables: For scalable setups, use process.env.HTTPS_PROXY or process.env.HTTP_PROXY to populate proxy configuration rather than hardcoding credentials into source code.