API Reference

WhatsApp API

37 endpoints for messaging, broadcasts, contacts, templates, phone numbers, and business profile. One REST API.

Quick Start

1.
Get API Key
Sign up for free and get your API key in seconds.
2.
Connect Account
Use our OAuth flow to connect WhatsApp accounts.
3.
Start Posting
Make API calls to post content to WhatsApp.

Send a WhatsApp Template Message

JavaScript

const response = await fetch('https://zernio.com/api/v1/posts', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer YOUR_API_KEY',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    platforms: [{
      platform: 'whatsapp',
      accountId: 'acc_waba123'
    }],
    platformSpecificData: {
      to: '+1234567890',
      template: {
        name: 'order_confirmation',
        language: { code: 'en' },
        components: [{
          type: 'body',
          parameters: [
            { type: 'text', text: 'John' },
            { type: 'text', text: 'ORD-12345' }
          ]
        }]
      }
    },
    publishNow: true
  })
});

const post = await response.json();
console.log(post.post._id); // '65f1c0a9e2b5af0012ab34cd'

WhatsApp Endpoints

POST/v1/whatsapp/bulk

Send text, template, media, or interactive messages to one or more recipients

POST/v1/whatsapp/broadcasts

Create a broadcast campaign with template and recipient list

GET/v1/whatsapp/broadcasts

List all broadcasts for an account, sorted by creation date

POST/v1/whatsapp/broadcasts/{id}/send

Send a broadcast campaign immediately

POST/v1/whatsapp/broadcasts/{id}/schedule

Schedule a broadcast for a future time

GET/v1/whatsapp/templates

List all message templates from your WABA (fetched from Meta Cloud API)

POST/v1/whatsapp/templates

Create a new template (submitted to Meta for approval)

PUT/v1/whatsapp/templates/{name}

Update an existing message template

DELETE/v1/whatsapp/templates/{name}

Delete a message template

GET/v1/whatsapp/contacts

List contacts with filtering by tags, groups, and opt-in status

POST/v1/whatsapp/contacts

Create a new WhatsApp contact

POST/v1/whatsapp/contacts/import

Bulk import contacts from CSV or JSON

PUT/v1/whatsapp/contacts/bulk

Bulk update contacts (tags, groups, fields)

GET/v1/whatsapp/groups

List all contact groups with member counts

GET/v1/whatsapp/phone-numbers

List all purchased WhatsApp phone numbers

GET/v1/whatsapp/phone-numbers/available

Search available US numbers for purchase

POST/v1/whatsapp/phone-numbers/purchase

Purchase a WhatsApp-ready phone number

POST/v1/whatsapp/phone-numbers/{id}/verify

Complete phone number verification

GET/v1/whatsapp/business-profile

Get WhatsApp Business profile (about, address, description)

PUT/v1/whatsapp/business-profile

Update WhatsApp Business profile fields

View full API reference →

Media Requirements

Type	Format	Max Size	Notes
Image	JPEG, PNG	5 MB	Supported in template headers and media messages
Video	MP4 (H.264/AAC)	16 MB	Supported in template headers and media messages
Audio	AAC, MP4, MPEG, AMR, OGG	16 MB	Voice and audio messages
Document	PDF, DOC, XLS, PPT, etc.	100 MB	Any common document format supported

Zernio automatically transcodes and optimizes media for WhatsApp's requirements.

API Limits

WhatsApp enforces per-phone-number messaging tiers based on your quality rating (1K, 10K, 100K, unlimited). Zernio handles rate limit errors (131047) with automatic retries and exponential backoff.

Zernio handles all rate limiting automatically. We queue and retry requests as needed.

Features

✓37 dedicated WhatsApp endpoints (messaging, broadcasts, contacts, templates, phone numbers, profile)
✓No Meta developer app or Business Manager required. One-click Embedded Signup
✓Broadcast campaigns: send to 100 recipients per request with per-user template variables
✓Full template CRUD: create, list, update, delete. We track category changes to prevent surprise billing
✓Contact CRM: bulk import, tags, groups, opt-in tracking, search and segmentation
✓Phone number provisioning: search, purchase, and verify WhatsApp-ready US numbers via API
✓Business profile management: read and update about, description, address, email, websites
✓24-hour messaging window handled automatically. Clear errors, no silent failures
✓Webhook delivery for incoming messages, delivery status, and read receipts
✓We absorb Meta's breaking changes so your integration keeps working

Response Example

Response

JSON

{
  "post": {
    "_id": "65f1c0a9e2b5af0012ab34cd",
    "status": "published",
    "platforms": [{
      "platform": "whatsapp",
      "accountId": { "_id": "acc_waba123", "username": "My Business" },
      "status": "published",
      "platformPostId": "wamid.abc123"
    }],
    "publishedAt": "2025-01-10T10:30:00Z"
  },
  "message": "Post published successfully"
}

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