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Sling API v2 is the multi-channel messaging API. You authenticate once with a bearer token and reach recipients on whichever channel fits the message — SMS, RCS, Truecaller, WhatsApp, or Email. v2 also adds a universal POST /send endpoint, multi-recipient sends, scheduled delivery, and richer lookups for phone numbers and RCS capability.

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What’s new in v2

  • Universal send endpoint — POST /send routes by channel so one integration can deliver across SMS, RCS, Truecaller, WhatsApp, and Email.
  • More channels — Native endpoints for send-whatsapp and send-email join SMS, RCS, and Truecaller.
  • Multi-recipient sends — Each send endpoint accepts to, contact, contacts[], group, groups[], or raw numbers in one call.
  • Scheduling and references — Use send_on to schedule delivery and reference to set your own message ID.
  • Lookups — POST /phone-number-check and POST /rcs-capability-check return network, country, and RCS capability for any number.
  • Account details — GET /details returns the authenticated user’s profile, balance, and currency.

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What Sling offers

  • SMS — Transactional, promotional, and OTP text messages.
  • RCS — Rich messages with cards, carousels, images, and interactive suggestion chips. Set fallback_sms to deliver as SMS when RCS is unavailable, and fallback_sms_sender for the SMS Sender ID (for example, Sling while sender is RCS).
  • Truecaller messaging — Branded, verified messages delivered through Truecaller. Set fallback_sms and fallback_sms_sender to fall back to SMS when Truecaller delivery is not possible.
  • WhatsApp — Business messaging through approved WhatsApp sender IDs.
  • Email — Transactional and promotional email through Sling’s email channel.
  • Contact management — Create groups and add individual or bulk contacts to target with one call.
  • Delivery status — Look up the status of any sent message by its message_id.
  • Balance API — Read your available messaging credit and currency at any time.
  • Form submissions — Auto-enroll inbound form submissions into your automations.

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How it works

Every Sling API request follows the same pattern: include your API token in the Authorization header and send a JSON body to the appropriate endpoint. The API returns JSON with a status field ("success" or "fail") along with channel-specific data such as message_id, credit_used, and currency. Authentication uses bearer tokens. Get your token from the dashboard or exchange your email and password for one through POST /auth.

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Base URL

All v2 endpoints share the following base URL: 
https://app.sling.com.ng/api/v2
Append the endpoint path to this base URL for every request. For example, to send a message you call POST https://app.sling.com.ng/api/v2/send.

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Required headers

Include these headers on every authenticated request:
HeaderValue
Acceptapplication/json
AuthorizationBearer {YOUR_API_TOKEN}
Content-Typeapplication/json (POST/PUT requests)
Replace {YOUR_API_TOKEN} with the token from your dashboard. See Authentication for token instructions.

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Migration from v1

v2 is backwards-compatible in spirit — same bearer token, same response shape, same status convention — but several endpoint paths and shapes changed. Notable differences:
Areav1v2
Universal sendingNot availablePOST /send with channel field
RCS capabilityGET /rcs/check-capability/{phone}POST /rcs-capability-check
Phone lookupNot availablePOST /phone-number-check
Account infobalance onlybalance + details
ChannelsSMS, RCS, TruecallerSMS, RCS, Truecaller, WhatsApp, Email
Multi-recipientLimited (group, contact)to, contact, contacts[], group, groups[], numbers
SchedulingNot availablesend_on parameter
The v1 documentation remains available for existing integrations.

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Next steps

Authentication

Get your API token and learn how to attach it to every request.

Quick Start

Send your first multi-channel message in under 5 minutes.

Universal send

Use a single endpoint for SMS, RCS, Truecaller, WhatsApp, and Email.

API reference

Browse every v2 endpoint with request and response fields.
Have questions beyond the scope of this documentation? Email the Sling team at [email protected].