Send OTP

post

https://www.fast2sms.com/dev/otp/send

Send an OTP to a mobile number using a predefined OTP template. You can customize the OTP length, expiry, and provide values for variables in your DLT template.

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This endpoint allows you to send an OTP to a mobile number. You can either provide your own OTP or let Fast2SMS generate one for you. If your template requires passing the OTP value in multiple variables, pass {otp} in variables_values (e.g. variables_values: "value1|{otp}" or "{otp}|{otp}").

Body Params

mobile

string

required

^[0-9]{10}$

10-digit Indian mobile number.

otp_id

string

required

Your unique OTP Template ID.

otp_expiry

integer

1 to 10080

Defaults to 15

OTP expiry time in minutes (Min: 1, Max: 10080, Default: 15).

otp_length

integer

4 to 10

Defaults to 6

OTP length (Min: 4, Max: 10, Default: 6).

otp

string

Optional: Pass your own OTP value if you don't want Fast2SMS to generate otp. (max 10)

variables_values

string

Values of {#var#} variables used in the template (if any), separated by pipe (|). Pass {otp} to send the original OTP value in multiple variables.

udf1

string

User Defined Field 1 – Optional custom value passed via API and returned in the webhook for your internal reference or tracking.

udf2

string

User Defined Field 2 – Optional custom value passed via API and returned in the webhook for your internal reference or tracking.

udf3

string

User Defined Field 3 – Optional custom value passed via API and returned in the webhook for your internal reference or tracking.

Headers

Authorization

string

required

Defaults to YOUR_API_KEY

Provide "YOUR_API_KEY".

Responses

200OTP sent successfully

400Bad Request - Validation or logic error

401Unauthorized - Invalid or missing Authorization key