Best Fax API for Developers — REST API Comparison & Integration Guide (2026)

Send and receive faxes programmatically with a modern REST API. Compare features, pricing, and HIPAA compliance across top fax API providers—with code examples in cURL, Python, and Node.js.

What Is a Fax API?

A fax API (Application Programming Interface) allows developers to send, receive, and manage faxes programmatically through HTTP requests—without physical fax machines, phone lines, or manual intervention. Modern fax APIs use RESTful architecture, meaning you interact with them using standard HTTP methods (GET, POST, PUT, DELETE) and receive responses in JSON format.

Think of a fax API as a bridge between your application and the global fax network. Your software makes an API call with a document and a recipient’s fax number, and the API provider handles the T.38 or T.30 fax protocol transmission on their infrastructure. The result? Your app sends a fax the same way it would send an email or an SMS—with a single HTTP request.

Common Fax API Use Cases

Fax APIs are essential in industries where fax remains a regulatory or operational requirement:

• Electronic Health Records (EHR): Hospitals and clinics use fax APIs to transmit patient records, lab results, and referral letters between providers. HIPAA compliance makes a secure fax API mandatory in healthcare.
• Customer Relationship Management (CRM): Legal firms and insurance companies integrate fax APIs into their CRM platforms to send contracts, claims, and signed documents automatically.
• Enterprise Resource Planning (ERP): Manufacturing and supply-chain businesses use fax APIs to exchange purchase orders, invoices, and shipping confirmations with partners who still rely on fax.
• Government & Compliance: Federal and state agencies often require fax for regulatory filings, license applications, and official correspondence.

Whether you’re building a healthcare platform, a legal document management system, or an enterprise workflow—a fax API lets you integrate fax capabilities directly into your stack. For a broader look at how online faxing works, see our guide on how to send a fax online.

Why Developers Need a Fax API

If your application touches healthcare, legal, financial, or government workflows, you’ll almost certainly encounter a fax requirement. Here are four key reasons developers choose a fax API over manual or legacy solutions:

Fax.plus API Features at a Glance

Here’s a detailed breakdown of what the Fax.plus REST API offers developers:

Fax API Code Examples

Below are working examples showing how to send a fax using the Fax.plus API in three popular languages. Replace YOUR_ACCESS_TOKEN and YOUR_USER_ID with your actual credentials from the Fax.plus developer dashboard.

cURL — Send a Fax

curl -X POST "https://restapi.fax.plus/v2/accounts/YOUR_USER_ID/faxes" \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "to": ["+12025551234"],
    "files": ["https://example.com/document.pdf"],
    "comment": "Invoice #1042 - sent via API"
  }'

Python — Send a Fax with requests

import requests

API_URL = "https://restapi.fax.plus/v2/accounts/YOUR_USER_ID/faxes"
ACCESS_TOKEN = "YOUR_ACCESS_TOKEN"

headers = {
    "Authorization": f"Bearer {ACCESS_TOKEN}",
    "Content-Type": "application/json"
}

payload = {
    "to": ["+12025551234"],
    "files": ["https://example.com/document.pdf"],
    "comment": "Invoice #1042 - sent via Python"
}

response = requests.post(API_URL, json=payload, headers=headers)

if response.status_code == 200:
    fax_id = response.json().get("id")
    print(f"Fax sent successfully. ID: {fax_id}")
else:
    print(f"Error: {response.status_code} - {response.text}")

Node.js — Send a Fax with axios

const axios = require('axios');

const API_URL = 'https://restapi.fax.plus/v2/accounts/YOUR_USER_ID/faxes';
const ACCESS_TOKEN = 'YOUR_ACCESS_TOKEN';

async function sendFax() {
  try {
    const response = await axios.post(API_URL, {
      to: ['+12025551234'],
      files: ['https://example.com/document.pdf'],
      comment: 'Invoice #1042 - sent via Node.js'
    }, {
      headers: {
        'Authorization': 'Bearer ' + ACCESS_TOKEN,
        'Content-Type': 'application/json'
      }
    });

    console.log('Fax sent successfully. ID: ' + response.data.id);
  } catch (error) {
    console.error('Error: ' + error.response?.status + ' - ' + error.response?.data);
  }
}

sendFax();

Each example sends a single-page PDF fax to a US phone number. The API responds with a fax ID you can use to track delivery status via webhooks or the status endpoint.

Fax API Comparison: Fax.plus vs Competitors (2026)

We evaluated the top fax API providers based on features, pricing, compliance, and developer experience. Here’s how they compare:

Note: Twilio officially deprecated its Fax API in 2021, but some legacy accounts retain access. We do not recommend it for new projects. For the most reliable and actively maintained option, we recommend Fax.plus.

For a broader comparison that includes consumer-facing features, see our best online fax services roundup.

Fax API Integration Use Cases

Here are four real-world scenarios where a fax API transforms business workflows:

These use cases share a common theme: the fax API eliminates manual steps, reduces errors, and creates an auditable communication trail. Whether you’re in healthcare or finance, the integration pattern is the same—trigger a fax from application logic, track delivery via webhooks, and store confirmations in your database.

Fax API Pricing — What Does It Cost?

Fax API pricing typically follows a per-page model with volume discounts at higher tiers. Here’s how Fax.plus structures its API pricing:

The Free tier is ideal for development and testing—you get full API access with 10 pages per month at no cost. For production workloads, the Business plan offers the best per-page economics. Enterprise customers can negotiate custom volume rates and SLAs with dedicated support.

All paid plans include HIPAA compliance (with BAA), priority webhook delivery, and higher rate limits (300 requests/minute vs. 60 on the free tier).

Getting Started with the Fax.plus API

You can send your first fax in under five minutes. Here’s the three-step process:

The entire process—from account creation to a successfully delivered test fax—typically takes less than five minutes. The Fax.plus documentation includes interactive API references, a Postman collection, and step-by-step tutorials for every endpoint.

Fax.plus API: Pros & Cons

Frequently Asked Questions About Fax APIs

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