What is an ID Collision? (A Simple Explanation)

Imagine you're giving out raffle tickets at a party. Each ticket needs a unique number. A "collision" is what would happen if you accidentally gave out the same number to two different people. It would cause confusion and problems! In the digital world, when our apps need to create unique IDs for things like user accounts, order numbers, or posts, the same problem exists. If the app accidentally generates the same ID twice, it can lead to bugs, data corruption, or even security issues. **Nano ID** is a very popular tool that programmers use to generate these IDs because it's incredibly good at avoiding collisions. It's like having a raffle ticket machine that can print a mind-boggling number of unique tickets.

This calculator is designed to help you understand just how safe your Nano ID setup is. It's built on a famous math concept called the "Birthday Problem," which shows that you need surprisingly few people in a room to have a good chance of two of them sharing a birthday. Our tool takes this idea and applies it to your IDs. It looks at the characters you're using (your "alphabet") and the length of your ID to figure out just how many unique possibilities there are. Then, it tells you how long it would take, at the speed you're generating IDs, to reach a 1% chance of a collision. It turns an abstract mathematical risk into a real-world timeframe that's easy to understand, like "150 years" or "2 billion years," giving you confidence that your system is safe.

How to Use the Calculator

Finding out how safe your IDs are is a simple, three-step process that updates in real-time:

1. Choose Your Alphabet: You can start with a common preset from the dropdown menu, like the standard URL-friendly Nano ID alphabet or just numbers. If you have a specific set of characters, choose "Custom" and type them into the box below.
2. Set Your ID Length: Enter the number of characters you plan to use for each ID. You'll see that even a small increase in this number makes a massive difference in safety.
3. Enter Your Speed: Give a rough estimate of how many IDs your system will need to generate every second. For most websites, 1,000 per second is a very high and safe estimate.

As you change any of these values, the results will instantly update. You'll see the estimated time it would take to have a tiny 1% chance of a single collision, giving you a clear picture of how robust your ID system is.

Tips for Choosing Your ID Settings

• Length is Your Best Friend: The single most powerful way to prevent collisions is to increase the length of your ID. As you'll see when you play with the calculator, increasing the length from 10 to 12 characters can change the collision time from hours to centuries. The default Nano ID length of 21 is famously overkill for almost any application on Earth.
• A Bigger Alphabet is Better: Using a larger, more diverse set of characters for your alphabet also dramatically increases the number of unique IDs you can create. Nano ID's default alphabet of 64 characters is an excellent and safe choice because it avoids symbols that can cause problems in URLs.
• Why a 1% Chance?: You might wonder why we calculate the time to a 1% probability instead of 100%. This is a very common and conservative benchmark used in cryptography and computer science. If the time to reach even a tiny 1% chance of a collision is measured in thousands or millions of years, you can be extremely confident that the risk of it ever happening in the real world is practically zero.