# The serve command

The serve command is used to preview a book by serving it via HTTP at `localhost:3000` by default:

    mdbook serve

The `serve` command watches the book’s `src` directory for changes, rebuilding the book and refreshing clients for each change; this includes re-creating deleted files still mentioned in `SUMMARY.md`! A websocket connection is used to trigger the client-side refresh.

Note: The `serve` command is for testing a book’s HTML output, and is not intended to be a complete HTTP server for a website.

#### Specify a directory

The `serve` command can take a directory as an argument to use as the book’s root instead of the current working directory.

    mdbook serve path/to/book

### Server options

The `serve` hostname defaults to `localhost`, and the port defaults to `3000`. Either option can be specified on the command line:

    mdbook serve path/to/book -p 8000 -n 127.0.0.1

#### `--open`

When you use the `--open` (`-o`) flag, mdbook will open the book in your default web browser after starting the server.

#### `--dest-dir`

The `--dest-dir` (`-d`) option allows you to change the output directory for the book. Relative paths are interpreted relative to the book’s root directory. If not specified it will default to the value of the `build.build-dir` key in `book.toml`, or to `./book`.

#### `--watcher`

There are different backends used to determine when a file has changed.

- `poll` (default) — Checks for file modifications by scanning the filesystem every second.
- `native` — Uses the native operating system facilities to receive notifications when files change. This can have less constant overhead, but may not be as reliable as the `poll` based watcher. See these issues for more information: #383 #1441 #1707 #2035 #2102

#### Specify exclude patterns

The `serve` command will not automatically trigger a build for files listed in the `.gitignore` file in the book root directory. The `.gitignore` file may contain file patterns described in the gitignore documentation. This can be useful for ignoring temporary files created by some editors.

Note: Only the `.gitignore` from the book root directory is used. Global `$HOME/.gitignore` or `.gitignore` files in parent directories are not used.