If you’re building an app that needs SMS verification or programmatic access to virtual numbers, integrating an API is generally more efficient than requiring manual dashboard use. Here’s the typical process, step by step.
Step 1: Get API Access and Credentials
Sign up for a provider offering API access — GearSMS states this as a specific feature for developer integration. (Disclosure: eSIMOTP is operated by the same team as GearSMS.) After signup, you’ll typically receive an API key or token from your account dashboard, required to authenticate your requests.
Step 2: Review the API Documentation
Before writing any code, review the provider’s documentation for:
- Available endpoints (e.g., requesting a number, checking for received messages, releasing a number)
- Authentication method (typically an API key passed in request headers)
- Rate limits, since most providers cap how many requests you can make in a given time period
- Response formats, usually JSON, detailing what fields to expect back
Step 3: Request a Number Programmatically
Most virtual number APIs follow a similar pattern: you send a request specifying the country and service you need a number for, and the API returns an available number along with an identifier for that specific rental session.
Step 4: Poll or Listen for Incoming Messages
Depending on the provider’s API design, you’ll either:
- Poll an endpoint periodically to check if a verification code has arrived, or
- Use a webhook, if the provider supports it, so incoming messages are pushed to your application automatically rather than requiring repeated polling
Webhooks are generally more efficient for production use, since they avoid unnecessary repeated requests.
Step 5: Handle the Received Code
Once your application receives the verification code, extract it (typically from the message body via a simple parsing pattern, since OTP messages are usually short and consistently formatted) and use it to complete whatever verification flow your application is handling on behalf of the user.
Step 6: Release or Renew the Number
Depending on whether you used a temporary or long-term number, release the number back to the pool once you’re done with it (for temporary use), or manage renewal if you’re using a long-term rental tied to an ongoing account.
Common Integration Pitfalls
Not handling rate limits gracefully. If your application makes requests faster than the provider allows, build in retry logic with backoff rather than failing outright.
Assuming instant delivery. SMS delivery can occasionally be delayed for reasons unrelated to your integration — see our guide on why OTP delivery sometimes lags for the general causes, which apply regardless of which API you’re using.
Not testing across multiple countries if you support international numbers. Behavior, formatting, and delivery reliability can vary by country, so test with real numbers from each region you intend to support before launching.
Frequently Asked Questions
Do I need a paid plan to access a virtual number API?
This depends on the provider — check the specific pricing and access tiers, since some offer limited free testing access before requiring a paid plan for production use.
Is polling or webhooks better for receiving codes?
Webhooks are generally more efficient for production applications, since they avoid the overhead and delay of repeated polling requests, if the provider supports them.
Can I use a virtual number API for numbers in multiple countries?
Most providers offering API access support requesting numbers from multiple countries, though available countries vary by provider — check current documentation.
What happens if my application exceeds the API’s rate limit?
Typically, requests beyond the limit are rejected or delayed until the limit window resets — build retry logic with backoff to handle this gracefully rather than failing outright.
Do I need to manually release a temporary number after use?
This depends on the provider — some numbers are automatically released after a session timeout, while others may require an explicit release call via the API.
