---
breadcrumbs:
- - /developers
  - For Developers
page_name: shutdown
title: Shutdown
---

[TOC]

## Browser Process Shutdown

### Stopping the UI Message Loop

*   A UI event is received that leads to BrowserList::RemoveBrowser()
            (closing the window, closing the last tab, keyboard shortcut for app
            termination, etc), which leads to
            g_browser_process->ReleaseModule()
*   If it's the last reference to g_browser_process, then we begin
            application termination.
    *   Note that Mac keeps the application alive even without browser
                windows by adding an extra g_browser_process->AddRefModule().
*   The last BrowserProcessImpl::ReleaseModule() call posts a task to
            the message loop to exit
*   Notification content::NOTIFICATION_APP_TERMINATING is broadcast
*   The UI message loop eventually stops running, we exit out of
            RunUIMessageLoop(). Note that all other main browser threads are
            still running their message loops. So even though the main (UI)
            thread outlives all other joined browser threads, its MessageLoop
            terminates first.

### BrowserProcessImpl deletion

*   After exiting the UI message loop, the shutdown sequence is started
            in BrowserMainParts::RunMainMessageLoopParts, which calls
            PostMainMessageLoopRun.
*   In ChromeBrowserMainParts::PostMainMessageLoopRun:
    *   The ProcessSingleton is released.
    *   MetricsService (which records UMA metrics) is stopped, which:
        *   Creates a log (for future upload) of all remaining metrics.
        *   Records a successful shutdown.
        *   The persistent metrics file, on disk, remains in case other
                    metrics are updated after this point. Any such values will
                    be sent during the next run sometime after Browser startup.
    *   We persist Local State to disk.
    *   We delete g_browser_process, which:
        *   Deletes the ProfileManager (which deletes all the profiles
                    and persists their state, such as Preferences)
        *   Joins the watchdog, IO, CACHE, PROCESS_LAUNCHER threads, in
                    that order
        *   Shuts down the DownloadFileManager and SaveFileManager
        *   Joins the FILE thread
        *   Deletes the ResourceDispatcherHost which joins the WEBKIT
                    thread
        *   Joins the DB thread

### ContentMain() exit

*   The AtExitManager goes out of scope and destroys all
            Singletons/LazyInstances

## Renderer Process Shutdown

### Browser process triggers shutdown via:

*   Closing a tab (explain the sequence of events from UI thread objects
            to the IO thread termination of a renderer process)