e0330d82bd
Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
242 lines
10 KiB
Markdown
242 lines
10 KiB
Markdown
# FAQ
|
||
|
||
## Q: Who maintains Puppeteer?
|
||
|
||
The Chrome DevTools team maintains the library, but we'd love your help and
|
||
expertise on the project! See our
|
||
[contributing guide](https://pptr.dev/contributing).
|
||
|
||
## Q: What is the status of cross-browser support?
|
||
|
||
Official Firefox support is currently experimental. The ongoing collaboration
|
||
with Mozilla aims to support common end-to-end testing use cases, for which
|
||
developers expect cross-browser coverage. The Puppeteer team needs input from
|
||
users to stabilize Firefox support and to bring missing APIs to our attention.
|
||
|
||
From Puppeteer v2.1.0 onwards you can specify
|
||
[`puppeteer.launch({product: 'firefox'})`](./api/puppeteer.puppeteernode.launch)
|
||
to run your Puppeteer scripts in Firefox Nightly, without any additional custom
|
||
patches. While
|
||
[an older experiment](https://www.npmjs.com/package/puppeteer-firefox) required
|
||
a patched version of Firefox,
|
||
[the current approach](https://wiki.mozilla.org/Remote) works with “stock”
|
||
Firefox.
|
||
|
||
We will continue to collaborate with other browser vendors to bring Puppeteer
|
||
support to browsers such as Safari. This effort includes exploration of a
|
||
standard for executing cross-browser commands (instead of relying on the
|
||
non-standard DevTools Protocol used by Chrome).
|
||
|
||
## Q: What are Puppeteer’s goals and principles?
|
||
|
||
The goals of the project are:
|
||
|
||
- Provide a slim, canonical library that highlights the capabilities of the
|
||
[DevTools Protocol](https://chromedevtools.github.io/devtools-protocol/).
|
||
- Provide a reference implementation for similar testing libraries. Eventually,
|
||
these other frameworks could adopt Puppeteer as their foundational layer.
|
||
- Grow the adoption of headless/automated browser testing.
|
||
- Help dogfood new DevTools Protocol features...and catch bugs!
|
||
- Learn more about the pain points of automated browser testing and help fill
|
||
those gaps.
|
||
|
||
We adapt
|
||
[Chromium principles](https://www.chromium.org/developers/core-principles) to
|
||
help us drive product decisions:
|
||
|
||
- **Speed**: Puppeteer has almost zero performance overhead over an automated
|
||
page.
|
||
- **Security**: Puppeteer operates off-process with respect to Chromium, making
|
||
it safe to automate potentially malicious pages.
|
||
- **Stability**: Puppeteer should not be flaky and should not leak memory.
|
||
- **Simplicity**: Puppeteer provides a high-level API that’s easy to use,
|
||
understand, and debug.
|
||
|
||
## Q: Is Puppeteer replacing Selenium/WebDriver?
|
||
|
||
**No**. Both projects are valuable for very different reasons:
|
||
|
||
- Selenium/WebDriver focuses on cross-browser automation; its value proposition
|
||
is a single standard API that works across all major browsers.
|
||
- Puppeteer focuses on Chromium; its value proposition is richer functionality
|
||
and higher reliability.
|
||
|
||
That said, you **can** use Puppeteer to run tests against Chromium, e.g. using
|
||
the community-driven
|
||
[jest-puppeteer](https://github.com/smooth-code/jest-puppeteer). While this
|
||
probably shouldn’t be your only testing solution, it does have a few good points
|
||
compared to WebDriver:
|
||
|
||
- Puppeteer requires zero setup and comes bundled with the Chromium version it
|
||
works best with, making it
|
||
[very easy to start with](https://github.com/puppeteer/puppeteer/#getting-started).
|
||
At the end of the day, it’s better to have a few tests running chromium-only,
|
||
than no tests at all.
|
||
- Puppeteer has event-driven architecture, which removes a lot of potential
|
||
flakiness. There’s no need for evil “sleep(1000)” calls in puppeteer scripts.
|
||
- Puppeteer runs headless by default, which makes it fast to run. Puppeteer
|
||
v1.5.0 also exposes browser contexts, making it possible to efficiently
|
||
parallelize test execution.
|
||
- Puppeteer shines when it comes to debugging: flip the “headless” bit to false,
|
||
add “slowMo”, and you’ll see what the browser is doing. You can even open
|
||
Chrome DevTools to inspect the test environment.
|
||
|
||
## Q: Why doesn’t Puppeteer v.XXX work with Chromium v.YYY?
|
||
|
||
We see Puppeteer as an **indivisible entity** with Chromium. Each version of
|
||
Puppeteer bundles a specific version of Chromium – **the only** version it is
|
||
guaranteed to work with.
|
||
|
||
This is not an artificial constraint: A lot of work on Puppeteer is actually
|
||
taking place in the Chromium repository. Here’s a typical story:
|
||
|
||
- A Puppeteer bug is reported:
|
||
https://github.com/puppeteer/puppeteer/issues/2709
|
||
- It turned out this is an issue with the DevTools protocol, so we’re fixing it
|
||
in Chromium: https://chromium-review.googlesource.com/c/chromium/src/+/1102154
|
||
- Once the upstream fix is landed, we roll updated Chromium into Puppeteer:
|
||
https://github.com/puppeteer/puppeteer/pull/2769
|
||
|
||
However, oftentimes it is desirable to use Puppeteer with the official Google
|
||
Chrome rather than Chromium. For this to work, you should install a
|
||
`puppeteer-core` version that corresponds to the Chrome version.
|
||
|
||
For example, in order to drive Chrome 71 with puppeteer-core, use `chrome-71`
|
||
npm tag:
|
||
|
||
```bash
|
||
npm install puppeteer-core@chrome-71
|
||
```
|
||
|
||
## Q: Which Chromium version does Puppeteer use?
|
||
|
||
Find the version using one of the following ways:
|
||
|
||
- Look for the `chromium` entry in
|
||
[revisions.ts](https://github.com/puppeteer/puppeteer/blob/main/packages/puppeteer-core/src/revisions.ts).
|
||
To find the corresponding Chromium commit and version number, search for the
|
||
revision prefixed by an `r` in [OmahaProxy](https://omahaproxy.appspot.com/)'s
|
||
"Find Releases" section.
|
||
- Look for the `versionsPerRelease` map in
|
||
[versions.js](https://github.com/puppeteer/puppeteer/blob/main/versions.js)
|
||
which contains mapping between Chromium and the smallest Puppeteer version
|
||
that supports it.
|
||
|
||
## Q: Which Firefox version does Puppeteer use?
|
||
|
||
Since Firefox support is experimental, Puppeteer downloads the latest
|
||
[Firefox Nightly](https://wiki.mozilla.org/Nightly) when the `PUPPETEER_PRODUCT`
|
||
environment variable is set to `firefox`. That's also why the value of `firefox`
|
||
in
|
||
[revisions.ts](https://github.com/puppeteer/puppeteer/blob/main/packages/puppeteer-core/src/revisions.ts)
|
||
is `latest` -- Puppeteer isn't tied to a particular Firefox version.
|
||
|
||
To fetch Firefox Nightly as part of Puppeteer installation:
|
||
|
||
```bash
|
||
PUPPETEER_PRODUCT=firefox npm i puppeteer
|
||
# or "yarn add puppeteer"
|
||
```
|
||
|
||
#### Q: What’s considered a “Navigation”?
|
||
|
||
From Puppeteer’s standpoint, **“navigation” is anything that changes a page’s
|
||
URL**. Aside from regular navigation where the browser hits the network to fetch
|
||
a new document from the web server, this includes
|
||
[anchor navigations](https://www.w3.org/TR/html5/single-page.html#scroll-to-fragid)
|
||
and [History API](https://developer.mozilla.org/en-US/docs/Web/API/History_API)
|
||
usage.
|
||
|
||
With this definition of “navigation,” **Puppeteer works seamlessly with
|
||
single-page applications.**
|
||
|
||
#### Q: What’s the difference between a “trusted" and "untrusted" input event?
|
||
|
||
In browsers, input events could be divided into two big groups: trusted vs.
|
||
untrusted.
|
||
|
||
- **Trusted events**: events generated by users interacting with the page, e.g.
|
||
using a mouse or keyboard.
|
||
- **Untrusted event**: events generated by Web APIs, e.g. `document.createEvent`
|
||
or `element.click()` methods.
|
||
|
||
Websites can distinguish between these two groups:
|
||
|
||
- using an
|
||
[`Event.isTrusted`](https://developer.mozilla.org/en-US/docs/Web/API/Event/isTrusted)
|
||
event flag
|
||
- sniffing for accompanying events. For example, every trusted `'click'` event
|
||
is preceded by `'mousedown'` and `'mouseup'` events.
|
||
|
||
For automation purposes it’s important to generate trusted events. **All input
|
||
events generated with Puppeteer are trusted and fire proper accompanying
|
||
events.** If, for some reason, one needs an untrusted event, it’s always
|
||
possible to hop into a page context with `page.evaluate` and generate a fake
|
||
event:
|
||
|
||
```ts
|
||
await page.evaluate(() => {
|
||
document.querySelector('button[type=submit]').click();
|
||
});
|
||
```
|
||
|
||
#### Q: What features does Puppeteer not support?
|
||
|
||
You may find that Puppeteer does not behave as expected when controlling pages
|
||
that incorporate audio and video. (For example,
|
||
[video playback/screenshots is likely to fail](https://github.com/puppeteer/puppeteer/issues/291).)
|
||
There are two reasons for this:
|
||
|
||
- Puppeteer is bundled with Chromium — not Chrome — and so by default, it
|
||
inherits all of
|
||
[Chromium's media-related limitations](https://www.chromium.org/audio-video).
|
||
This means that Puppeteer does not support licensed formats such as AAC or
|
||
H.264. (However, it is possible to force Puppeteer to use a
|
||
separately-installed version Chrome instead of Chromium via the
|
||
[`executablePath` option to `puppeteer.launch`](./api/puppeteer.launchoptions.executablepath).
|
||
You should only use this configuration if you need an official release of
|
||
Chrome that supports these media formats.)
|
||
- Since Puppeteer (in all configurations) controls a desktop version of
|
||
Chromium/Chrome, features that are only supported by the mobile version of
|
||
Chrome are not supported. This means that Puppeteer
|
||
[does not support HTTP Live Streaming (HLS)](https://caniuse.com/#feat=http-live-streaming).
|
||
|
||
#### Q: I am having trouble installing / running Puppeteer in my test environment. Where should I look for help?
|
||
|
||
We have a
|
||
[troubleshooting](https://github.com/puppeteer/puppeteer/blob/main/docs/troubleshooting.md)
|
||
guide for various operating systems that lists the required dependencies.
|
||
|
||
#### Q: Chromium gets downloaded on every `npm ci` run. How can I cache the download?
|
||
|
||
The default download path is `node_modules/puppeteer/.local-chromium`. However,
|
||
you can change that path with the `PUPPETEER_DOWNLOAD_PATH` environment
|
||
variable.
|
||
|
||
Puppeteer uses that variable to resolve the Chromium executable location during
|
||
launch, so you don’t need to specify `PUPPETEER_EXECUTABLE_PATH` as well.
|
||
|
||
For example, if you wish to keep the Chromium download in `~/.npm/chromium`:
|
||
|
||
```sh
|
||
export PUPPETEER_DOWNLOAD_PATH=~/.npm/chromium
|
||
npm ci
|
||
|
||
# by default the Chromium executable path is inferred
|
||
# from the download path
|
||
npm test
|
||
|
||
# a new run of npm ci will check for the existence of
|
||
# Chromium in ~/.npm/chromium
|
||
npm ci
|
||
```
|
||
|
||
#### Q: I have more questions! Where do I ask?
|
||
|
||
There are many ways to get help on Puppeteer:
|
||
|
||
- [bugtracker](https://github.com/puppeteer/puppeteer/issues)
|
||
- [Stack Overflow](https://stackoverflow.com/questions/tagged/puppeteer)
|
||
|
||
Make sure to search these channels before posting your question.
|