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OTP Generator Online

Use this free OTP generator online to create secure one-time passcodes in seconds. Choose a length from 4 to 8 digits, generate up to 10 codes at once, and copy any code — or all of them — in one click. Every code is made on your device and never sent anywhere.

How it works

An OTP, or one-time passcode, is a short numeric code that proves you are who you say you are, exactly once. When you sign in from a new device, reset a password, or confirm a payment, the service creates a code, sends it to your phone or email, and waits for you to type it back. The code works only once and only for a few minutes. If you type it correctly in time, you are in. If the code expires, or if someone tries it later, it is worthless. That short life is the whole point: a password can be stolen and reused for months, but an OTP is dead within minutes.

This generator makes codes the same way a service does: it picks each digit at random, independently, using your browser's secure random number generator, crypto.getRandomValues. That matters, because a code built from a predictable pattern — a date of birth, a phone number, or a counting sequence — can be guessed. A truly random 6-digit code has no pattern at all. The generator never sends the code anywhere and never stores it: the code exists only on your screen until you copy it or close the page. Use it for test codes while you build a login system, for demo codes in a training session, or for practice while you learn how one-time codes work. It is not a replacement for the code your own bank or email provider sends you — always use the code your service sends when you are signing in for real.

The length setting controls how hard a code is to guess. Each extra digit multiplies the number of possible codes by ten. A 4-digit code has 10,000 possible values, from 0000 to 9999. A 5-digit code has 100,000. A 6-digit code has 1,000,000 possible values, from 000000 to 999999 — one hundred times more than a 4-digit code, while still short enough to type from memory. A 7-digit code has 10,000,000, and an 8-digit code has 100,000,000. Most services settle on 6 digits because it is the sweet spot: hard enough to guess in the few minutes the code is alive, and easy enough for a person to read and type. If you are testing a system, try 4 digits for a quick demo and 8 digits when you want to show the strongest option.

The count setting lets you make up to 10 codes at once, which is useful when you need a batch of test codes or a set of backup codes for a demo. The "make all codes different" box is on by default, so no code in the batch repeats another one. The "allow leading zeros" box is also on by default, and it matters more than it looks: if leading zeros are off, a 6-digit code can never start with 0, which cuts the number of possible codes from 1,000,000 to 900,000. Real services allow leading zeros — a code like 042817 is perfectly valid — so leave the box on unless the system you are testing rejects them.

Finally, the security note deserves repeating, because it is the one thing about OTPs that people get wrong. A legitimate service will never ask you for your OTP. Not by phone, not by text, not by email, and not in a chat window. The code is meant to go from the service to you, and then from you back into the service's own login page — never to another person. If someone calls and says they are from your bank and need your code to "verify your account" or "stop a fraud", that person is the fraud. Hang up, do not share the code, and contact the service yourself through its official website or app.

Worked example

Suppose you need a standard 6-digit OTP for a test login. Set the length to 6, the count to 1, and press Generate OTP. The tool might return a code such as 482913. Your code will be different, because every code is random — but the maths behind it is the same.

Step 1: Count the possible values. A 6-digit code has 6 positions, each with 10 possible digits (0 to 9).
Step 2: Multiply: 10 × 10 × 10 × 10 × 10 × 10 = 10⁶ = 1,000,000.
Step 3: So a 6-digit OTP has 1,000,000 possible values, from 000000 to 999999.

For comparison, a 4-digit code has only 10⁴ = 10,000 possible values, and an 8-digit code has 10⁸ = 100,000,000. That is why 6 digits is the default in this tool and in most real services: one million possibilities is far too many to guess in the few minutes before the code expires, while six digits is still easy to read and type.

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