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# Test data overview

By default, every virtual user sends requests with the same data during a performance test. You can provide test data to vary the behavior of virtual users and better simulate real-world traffic, for example by giving each virtual user a unique login, token, or payload.

* **[Use a data file to simulate virtual users](/docs/tests-and-scripts/performance-testing/test-data/performance-test-data-files/)** — Start with a CSV or JSON you attach and run, for a small, fixed set of values you don't need to reuse. Each row maps to one virtual user.
* **[Use a dataset to simulate virtual users](/docs/tests-and-scripts/performance-testing/test-data/performance-test-dataset/)** — The next step when you need more: reusable or live data, SQL queries, connections to live databases, and no file size limits. Datasets also let you control how rows are distributed across virtual users.