> For the complete documentation index, see [llms.txt](https://help.modelreef.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.modelreef.io/syntax/understanding-the-interface/driver-editor-screen.md).

# Driver Editor Screen

This article explains the **Driver Editor screen** in Model Reef.

You will learn:

* What a driver is in Model Reef.
* How to view and edit driver time series.
* How drivers connect to variables and formulas.

Drivers provide reusable inputs that shape variable behaviour across the model.

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### What the Driver Editor is for

Where the Variable Editor controls a single variable's behaviour, the Driver Editor controls shared **input series**, such as:

* Market growth rates.
* Unit prices.
* Volumes, headcounts or utilisation.
* FX rates or inflation.
* Seasonality indices.
* Other modifiers used in formulas.

Changing a driver can affect many variables at once.
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### Opening the Driver Editor

You can open the Driver Editor from:

* The drivers list within a branch or model.
* The Data Library viewer when you open a driver entry.
* A formula or variable that references a driver (via drill down).

Once open, you see the full time series for that driver across the model timeline.
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### Driver types

Model Reef groups drivers into three main classes:

* **Economic drivers**
  * Prices, inflation, FX, macro indices and similar.
* **Operational drivers**
  * Units, volumes, hours, headcount, utilisation and so on.
* **Modifier drivers**
  * Percentages, scalars, adjustment factors and scenario modifiers.

The driver type is mostly for clarity and organisation. It does not by itself create P\&L or cashflow entries until a variable uses the driver.
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### Editing driver values

In the Driver Editor you can:

* Enter values directly by period.
* Apply preset patterns such as growth, flat ranges or seasonal shapes.
* Import historical series from the Data Library or external sources.
* Copy and paste ranges from spreadsheets if needed.

Changes you make here update all variables and formulas that reference the driver.
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### Timing, frequency and interpolation

Drivers use the model's base periodicity, but you can:

* Define driver values at a coarser level and have Model Reef interpolate.
* Use schedules to apply different values in different periods.
* Apply seasonality patterns to repeat over each year.

For many use cases, drivers are smoother than variables and act as simple, intuitive assumption series.
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### Linking drivers to variables and formulas

Variables and formulas can use drivers in several ways:

* Direct multiplication, for example `Revenue = Units driver × Price driver`.
* Adjustment factors, for example `Opex = Base cost × Inflation driver`.
* Scenario toggles, for example `Volume × Scenario modifier driver`.

The Driver Editor does not show all uses of a driver, but you can usually drill down from variables to see which drivers they reference.
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### Documentation and collaboration

As with variables, you can:

* Add notes explaining what the driver represents and where the numbers come from.
* Attach source files, such as market reports or CSVs.
* Tag the driver for review or ownership.

Because drivers can affect many variables, good documentation here is particularly important.
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## Related articles

* [Selecting Driver Type](/syntax/drivers-syntax/selecting-driver-type.md)
* [Overriding Variables](/syntax/scenario-syntax/overriding-variables.md)
* [Accrual Logic](/help/drivers-variables-and-timing/accrual-logic.md)
* [Build a Driver Based Forecast](/how-tos/core-modelling/build-a-driver-based-forecast.md)