---
title: Check and apply
description: See what differs from your config, then fix only that.
---

```sh
dot check                           # everything in config/; changes nothing
dot apply                           # fix every difference
dot check dock                      # one file: config/dock.conf
dot apply keyboard repeat-rate 1    # try one setting, not saved anywhere
```

```text
✓ dock visibility hidden
~ keyboard repeat-rate 2
    NSGlobalDomain KeyRepeat: 5 → 2
~ system hostname your-mac
    ComputerName: Your MacBook Pro → your-mac  (sudo)
✓ shell init zsh
    · not from this repo: ~/.zshrc line(s) 1
! mouse secondary-click: expected right, left or off, got 'middle'
```

| Mark     | Meaning                                                           |
|----------|-------------------------------------------------------------------|
| `✓`      | matches                                                           |
| `~`      | differs; each indented line is an underlying value and its target |
| `→`      | changed by `apply`                                                |
| `!`      | an invalid value or a failed step; nothing changed for it         |
| `·`      | a note: information only, never a difference                      |
| `(sudo)` | needs your password; `apply` asks for it                          |

`check` never changes anything and never asks for a password or Touch ID.
`apply` changes only what differs, so running it twice is safe. At the end
it restarts the apps that need it and lists anything left for you, such as
logging out.

## Try before you keep

`dot apply <topic> <setting> <value>` applies one setting without saving it
anywhere. To keep it, add the same line to a file in `config/`.

## Ask what a line does

```sh
dot explain                       # every setting, and where config/ uses it
dot explain trackpad              # one topic
dot explain dock visibility       # one setting
dot explain brew cask ghostty     # one line
```

The more you give, the more it says. Given a whole line, it shows the line in
`config/` with the comment above it, and what it refers to on this Mac; for
a package, its description, version, and whether it's installed:

```text
brew cask <name>
    an app, font or prebuilt binary, e.g. 1password

    in config/apps.conf:
      # Terminal.
      brew cask ghostty

    ghostty: Terminal emulator that uses platform-native UI and GPU acceleration
      https://ghostty.org/
      version 1.3.1, installed 1.3.1
```

A line that isn't in `config/` yet is explained too, with a reminder to add
it. `explain` changes nothing.

Every setting dot knows is in the [settings reference](/docs/reference/settings).