---
title: "Configuration file anatomy | Grafana Labs"
description: "The three basic parts of an Alloy configuration file"
---

> For a curated documentation index, see [llms.txt](/llms.txt). For the complete documentation index, see [llms-full.txt](/llms-full.txt).

Section 4 · Reading Alloy configuration

The three basic parts of an Alloy configuration file

Estimated time: 1 min

## Configuration file anatomy

To read an Alloy configuration, start by recognizing its parts. An Alloy configuration file is made of attributes, expressions, and blocks. These elements describe the settings and behavior that Alloy loads.

### Attributes

Attributes are `key = value` pairs that configure individual settings:

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
url = "http://localhost:9090"
```

Here, `url` is the attribute name. The value on the right side of `=` comes from an expression.

### Expressions

Expressions compute the values that attributes use. An expression can be:

- A constant, such as `"localhost:9090"`
- A calculation, such as `(1 + 2) * 3`
- A standard library call, such as `sys.env("HOME")`

Alloy evaluates an expression before assigning its result to an attribute. There is a fourth kind of expression, a reference to another component’s export, that you trace later in this section.

### Blocks

Blocks group related attributes and nested blocks between `{` and `}`. Most blocks you read define components. A component block has a name and a label:

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
local.file "example" {
  filename = "/tmp/example.txt"
}
```

Here, `local.file` is the component name, `"example"` is the label, and `filename` is an attribute inside the block.