## TL;DR

Chrome stopped answering Selenium's commands, usually because a navigation never finished (a pending request, a download dialog, or an unload handler hanging). Do not just raise the timeout; set an explicit page-load timeout and a less strict load strategy so one stuck resource cannot hang the whole session.

## Error

```text
selenium.common.exceptions.TimeoutException: Message: timeout: Timed out receiving message from renderer: 300.000
```

## Steps

1. Set an explicit page-load timeout so it fails fast instead of hanging on the default: `driver.set_page_load_timeout(60)` in Python, or `driver.manage().timeouts().pageLoadTimeout(Duration.ofSeconds(60))` in Java. Expected: slow pages raise TimeoutException at 60s with a clear stack.
2. Switch the page-load strategy to eager so Selenium returns after DOM content loads: set `pageLoadStrategy: 'eager'` in Chrome options. Expected: navigations return before slow subresources finish.
3. Replace implicit waits with explicit ones: `WebDriverWait(driver, 10).until(EC.presence_of_element_located((By.ID, "app")))`. Expected: waits target the element you need, not the renderer.
4. Check for renderer blockers: file-download dialogs, beforeunload handlers, or pages opening print preview. Expected: removing or handling the blocker stops the hang.
5. In headless CI add `--disable-dev-shm-usage` to Chrome options (tiny shared memory crashes the renderer). Expected: renderer crashes disappear.

## When to use

- The error message mentions the renderer.
- It happens on driver.get or on a click that triggers navigation.
- It is flaky in Docker but fine on your laptop.

## When not to use

- NoSuchElementException (the page loaded; the selector is wrong).
- SessionNotCreatedException (driver and browser versions disagree).
- Timeouts in your own test code rather than in Selenium calls.

## Tool compatibility

- Selenium 4.x in Python, Java, or JavaScript bindings.
- Chrome and Chromedriver 110 and newer.

## Variant phrasings

### Timed out receiving message from renderer: 10.000

A script timeout, not a page load: some JavaScript ran past the script timeout. Raise it or fix the script.

### only in headless

Missing flags or a resource limit in the container. Start with --disable-dev-shm-usage.

### right after a file download starts

The download dialog blocks the renderer. Set a default download directory so no dialog appears.

## Why it happens

Selenium talks to Chrome over the DevTools protocol; if the renderer is stuck (an infinite unload handler, a huge page, a tab crashed from shared-memory exhaustion), commands queue with no reply until the timeout fires.

## Edge cases

- `pageLoadStrategy: 'none'` returns immediately, but then every later command needs its own explicit wait.
- Raising the renderer timeout without fixing the cause just moves the hang later.
- Downloads need a preset download directory, otherwise the dialog blocks the renderer every time.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_Jp8BetKYL4f04QaEApvCpA