Why Indian stores need OTP verification<\/h2>\n
India’s ecommerce runs on cash on delivery more than almost any market, and that changes what “verification” means for a store:<\/p>\n
- \n
- Fake COD orders.<\/strong> A wrong or made-up mobile number costs you shipping both ways, packaging, and a blocked unit of stock. One OTP at checkout confirms a real, reachable customer before the parcel leaves.<\/li>\n
- Account takeovers and password pain.<\/strong> Customers reuse weak passwords, then forget them. OTP login removes the password entirely: the phone becomes the key, and support stops answering reset emails all day.<\/li>\n
- Coupon and signup abuse.<\/strong> “First order 50% off” invites one customer with ten fake accounts. Verified mobile numbers make each identity cost a real SIM, which kills the economics of abuse.<\/li>\n
- Dead contact data.<\/strong> Delivery riders call before arriving; marketing sends order updates. Both fail if the number was typed wrong. Verification at entry keeps the whole downstream chain working.<\/li>\n
- Customer trust.<\/strong> An OTP at signup or checkout signals a store that takes security seriously, the same pattern customers know from their bank and UPI apps.<\/li>\n<\/ul>\n
\n![\"Verification](\"https:\/\/www.fast2sms.com\/help\/wp-content\/uploads\/2026\/07\/verification-funnel.png\")
Every unverified number that enters your funnel costs money further down. OTP moves the filter to the top.<\/figcaption><\/figure>\n What a good OTP SMS API handles for you<\/h2>\n
Sending a text is the easy part. A production OTP system also needs code generation, expiry, retry limits, resend windows, storage that never leaks, DLT-compliant templates, and a fallback when SMS does not arrive. The Fast2SMS OTP API does all of that server-side:<\/p>\n
- \n
- You never generate or store OTPs.<\/strong> The API creates the code, sends it, and checks it on verify. Your database never holds an OTP, so there is nothing to leak.<\/li>\n
- Smart OTP fallback.<\/strong> An OTP ID can send on WhatsApp first and automatically fall back to DLT SMS if WhatsApp delivery fails, or the reverse. One API call, two delivery paths.<\/li>\n
- Resend built in.<\/strong> Customers can request the code again within a 10 minute window, without your code juggling timers.<\/li>\n
- DLT handled.<\/strong> Ready OTP templates and free DLT support cover the compliance side of SMS in India.<\/li>\n<\/ul>\n
\n![\"Smart](\"https:\/\/www.fast2sms.com\/help\/wp-content\/uploads\/2026\/07\/smart-otp-flow.png\")
Smart OTP: one send call, WhatsApp first, SMS fallback automatic. Your code never knows the difference.<\/figcaption><\/figure>\n Step 1: Create your OTP ID<\/h2>\n
Signup free at fast2sms.com<\/a>, open the Smart OTP<\/strong> section and create an OTP ID. That is where you pick the channel (SMS, WhatsApp, or WhatsApp with SMS fallback), the template, and the sender. The OTP ID is the only thing your code needs besides the API key from the Dev API section.<\/p>\n
\n![\"Smart](\"https:\/\/www.fast2sms.com\/help\/wp-content\/uploads\/2026\/06\/Screenshot-2026-06-24-at-9.15.02-PM.png\")
One OTP ID holds channel, template and fallback settings, so code stays one line simple.<\/figcaption><\/figure>\n Step 2: Send the OTP<\/h2>\n
curl --request POST \\\n --url https:\/\/www.fast2sms.com\/dev\/otp\/send \\\n --header 'Authorization: YOUR_API_KEY' \\\n --header 'accept: application\/json' \\\n --header 'content-type: application\/json' \\\n --data '{\n \"otp_id\": \"11111111\",\n \"mobile\": \"8888888888\"\n }'<\/code><\/pre>\nSuccess response:<\/p>\n
{\n \"return\": true,\n \"status_code\": 200,\n \"request_id\": \"lwdtp7cjyqxvfe9\",\n \"message\": \"OTP sent successfully\"\n}<\/code><\/pre>\nStep 3: Verify what the customer typed<\/h2>\n
curl --request POST \\\n --url https:\/\/www.fast2sms.com\/dev\/otp\/verify \\\n --header 'Authorization: YOUR_API_KEY' \\\n --header 'accept: application\/json' \\\n --header 'content-type: application\/json' \\\n --data '{\n \"mobile\": \"8888888888\",\n \"otp\": \"123456\"\n }'<\/code><\/pre>\n{\n \"return\": true,\n \"status_code\": 200,\n \"message\": \"OTP verified successfully\"\n}<\/code><\/pre>\nWrong or expired code returns
\"return\": false<\/code>, so one if-check gates your signup, login or COD confirmation. Full reference: send OTP<\/a> and verify OTP<\/a> at docs.fast2sms.com.<\/p>\nThe whole flow in PHP<\/h2>\n
<?php\n\/\/ 1. Send the OTP when the customer submits their mobile\n$ch = curl_init('https:\/\/www.fast2sms.com\/dev\/otp\/send');\ncurl_setopt_array($ch, array(\n CURLOPT_RETURNTRANSFER => true,\n CURLOPT_POST => true,\n CURLOPT_HTTPHEADER => array(\n 'Authorization: YOUR_API_KEY',\n 'Content-Type: application\/json',\n 'Accept: application\/json',\n ),\n CURLOPT_POSTFIELDS => json_encode(array(\n 'otp_id' => '11111111',\n 'mobile' => $customerMobile,\n )),\n));\n$send = json_decode(curl_exec($ch), true);\ncurl_close($ch);\n\nif (empty($send['return'])) {\n exit('Could not send OTP, try again.');\n}\n\n\/\/ 2. Later, verify the code the customer typed\n$ch = curl_init('https:\/\/www.fast2sms.com\/dev\/otp\/verify');\ncurl_setopt_array($ch, array(\n CURLOPT_RETURNTRANSFER => true,\n CURLOPT_POST => true,\n CURLOPT_HTTPHEADER => array(\n 'Authorization: YOUR_API_KEY',\n 'Content-Type: application\/json',\n 'Accept: application\/json',\n ),\n CURLOPT_POSTFIELDS => json_encode(array(\n 'mobile' => $customerMobile,\n 'otp' => $enteredOtp,\n )),\n));\n$verify = json_decode(curl_exec($ch), true);\ncurl_close($ch);\n\nif (!empty($verify['return'])) {\n \/\/ Verified: create the account, log the user in, or confirm the COD order\n} else {\n \/\/ Wrong or expired OTP: show an error, offer resend\n}<\/code><\/pre>\nNotice what is missing: no OTP generation, no expiry cron, no code comparison, no OTP column in your database. The API owns all of it. Need delivery events in your own system (mark verified numbers, alert on failures)? OTP webhooks push delivered and failed statuses to your endpoint: how webhooks work<\/a>.<\/p>\n
No code? The same API powers ready plugins<\/h2>\n
- \n
- WordPress:<\/strong> free plugin with OTP login<\/a> and signup verification; install from WordPress.org<\/a>.<\/li>\n
- WooCommerce:<\/strong> OTP verification for checkout and registration<\/a>, including COD confirmation.<\/li>\n
- Shopify:<\/strong> the official app covers storefront OTP login: integrate OTP with Shopify<\/a>.<\/li>\n
- Everything else:<\/strong> the two endpoints above work from any language or stack that can make an HTTPS POST.<\/li>\n<\/ul>\n
OTP SMS API vs building it yourself<\/h2>\n
\n\n\n
\n \n<\/th>\n Build in-house<\/th>\n Fast2SMS OTP API<\/th>\n<\/tr>\n<\/thead>\n \n OTP generation, expiry, storage<\/td>\n Your code, your database, your risk<\/td>\n Server-side, never touches your DB<\/strong><\/td>\n<\/tr>\n \n DLT registration and templates<\/td>\n You research and file<\/td>\n Ready templates + free DLT support<\/strong><\/td>\n<\/tr>\n \n When SMS does not arrive<\/td>\n Customer stuck, order lost<\/td>\n Smart OTP auto-falls back to WhatsApp or SMS<\/strong><\/td>\n<\/tr>\n \n Resend handling<\/td>\n More timers in your code<\/td>\n Built in, 10 minute window<\/strong><\/td>\n<\/tr>\n \n Cost structure<\/td>\n Developer time + gateway contracts<\/td>\n No setup or monthly fee, pay per message<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n What it costs<\/h2>\n
There is no setup fee, no monthly platform fee and no minimum commitment: you pay the per-message rate from your wallet, and only for what you send. WhatsApp OTPs bill on delivery basis with failed messages auto-refunded, at \u20b90.25 per authentication message (\u20b90.11 on high-volume plans). SMS OTPs go at your account’s DLT SMS rate. A slow month costs you nothing.<\/p>\n
Frequently asked questions<\/h2>\n
What is an OTP SMS API?<\/h3>\n
Two REST endpoints: one sends a one-time password to a mobile number, the other verifies the code the user entered. Your application calls them over HTTPS with an API key; the provider handles generation, delivery, expiry and checking.<\/p>\n
How fast do OTPs arrive?<\/h3>\n
OTP routes are prioritised for speed and typically arrive within seconds, with Smart OTP falling back to the second channel automatically when the first fails, so the customer is never left waiting on a dead channel.<\/p>\n
Do I need DLT registration to send OTP SMS?<\/h3>\n
SMS OTPs in India need DLT like all business SMS; Fast2SMS provides ready OTP templates and free DLT support. WhatsApp OTPs need no DLT at all, which is why many stores start with WhatsApp-first Smart OTP.<\/p>\n
Do I have to store OTPs in my database?<\/h3>\n
No, and you should not. The verify endpoint checks the code server-side; your system only ever sees verified or not verified.<\/p>\n
Can the customer ask for the OTP again?<\/h3>\n
Yes, resend works within a 10 minute window per send, without extra logic on your side.<\/p>\n
Which platforms can use this without code?<\/h3>\n
WordPress, WooCommerce and Shopify all have free official Fast2SMS plugins running on the same OTP API, covering login, registration and checkout verification.<\/p>\n
What does an OTP cost?<\/h3>\n
No monthly or setup fee; per-message billing only. WhatsApp authentication messages are \u20b90.25 (\u20b90.11 high volume) on delivery basis with auto refund for failures; SMS follows your DLT SMS rate.<\/p>\n
Where is the full API documentation?<\/h3>\n
At docs.fast2sms.com<\/a>, including send, verify and resend references. The wider product is covered in the Smart OTP guide<\/a> and the bulk SMS API guide<\/a>.<\/p>\n
Verify your first number today<\/h2>\n
Create your free account, make one OTP ID, and the two API calls above turn any signup form, login page or COD checkout into a verified one this afternoon.<\/p>\n
- WooCommerce:<\/strong> OTP verification for checkout and registration<\/a>, including COD confirmation.<\/li>\n
- Smart OTP fallback.<\/strong> An OTP ID can send on WhatsApp first and automatically fall back to DLT SMS if WhatsApp delivery fails, or the reverse. One API call, two delivery paths.<\/li>\n
- Account takeovers and password pain.<\/strong> Customers reuse weak passwords, then forget them. OTP login removes the password entirely: the phone becomes the key, and support stops answering reset emails all day.<\/li>\n