> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gists.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Variables

Like we've mentioned on the [gists](/essentials/gists) page, variables are placeholders in prompt templates.

## Variable format

Gist variables are wrapped in double curly brackets:

```mustache
{{variable}}
```

## Variable names rules

The variable name must starts with a letter and can only contain lowercase letters, numbers, and underscores:

```mustache
{{1variable}} # ❌
{{variable-1}} # ❌
{{Variable-1}} # ❌
{{variable_1}} # ✅
{{variable1}} # ✅
```

In addition, there must be no spaces between the variable name and the curly brackets:

```mustache
{{ variable }} # ❌
{{variable}} # ✅
```