# Can I generate a random string, number, or UUID/GUID in my script?

> Loadster has easy ways to generate random strings, numbers, or UUID/GUID for your load test scripts.

Source: https://loadster.com/faqs/generating-random-string-or-uuid/

Sometimes it's necessary to generate a random string, number, or UUID/GUID in your load test script.

To do this, you can call any of these functions:

* `randomalpha(len)` - Generates a random alphabetic string of the specified length (consisting of all ASCII letters).
* `randomnumeric(len)` - Generates a random numeric string of the specified length (consisting of digits 0-9).
* `randomalphanumeric(len)` - Generates a random alphanumeric string of the specified length (consisting of all ASCII letters and digits 0-9 at random).
* `uuid()` - Generates a 128-bit UUID in the form of a hyphenated hexadecimal string (8-4-4-4-12), for a total of 36 characters.

These functions can only be called from within an `${}` expression, similar to referencing a variable. For example:

`GET https://petstore.loadster.com/api/inventory?q=${randomalpha(2)}`

The `${randomalpha(2)}` section of this URL will be substituted at runtime with a random string of 2 letters.

More information is available in [Variables & Expressions](https://loadster.com/manual/variables-and-expressions/).

## When would it make sense to use random data?

### Dynamic POST or PUT bodies

Load testing a dynamic web application or API often requires that your script create resources on the server or submit
a web form via an HTTP POST or PUT request.

It's usually a good idea to submit different data with each such request. To do this, you can either use a
[dataset](https://loadster.com/manual/dynamic-datasets/) with predefined values, or generate the data randomly on the fly with
an [expression](https://loadster.com/manual/variables-and-expressions/).

### Cache busting

It's common for busy sites to be situated behind a caching proxy or web application firewall that caches
identical-looking requests to keep them from hitting your application servers. If you need to ensure that your load
test traffic hits the actual servers, bypassing such a caching layer, you can add random query strings to the URLs to
make them dynamic. For example:

`GET https://petstore.loadster.com/?_=${randomalpha(16)}`

In this URL we've employed an underscore query parameter with a random value, to make sure each request is different,
thereby bypassing the caching layer.