Scrapling/docs/fetching/dynamic.md

Introduction

Here, we will discuss the DynamicFetcher class (previously known as PlayWrightFetcher). This class provides flexible browser automation with multiple configuration options and some stealth capabilities.

As we will explain later, to automate the page, you need some knowledge of Playwright's Page API.

Basic Usage

You have one primary way to import this Fetcher, which is the same for all fetchers.

>>> from scrapling.fetchers import DynamicFetcher

Check out how to configure the parsing options here

Now, we will review most of the arguments one by one, using examples. If you want to jump to a table of all arguments for quick reference, click here

Notes:

1. Every time you fetch a website with this fetcher, it waits by default for all JavaScript to fully load and execute, so you don't have to (wait for the domcontentloaded state).
2. Of course, the async version of the fetch method is the async_fetch method.

This fetcher currently provides four main run options, which can be mixed as desired.

Which are:

1. Vanilla Playwright

DynamicFetcher.fetch('https://example.com')

Using it in that manner will open a Chromium browser and load the page. There are no tricks or extra features unless you enable some; it's just a plain PlayWright API.

2. Stealth Mode

DynamicFetcher.fetch('https://example.com', stealth=True)

It's the same as the vanilla Playwright option, but it provides a simple stealth mode suitable for websites with a small to medium protection layer(s).

Some of the things this fetcher's stealth mode does include:

• Patching the CDP runtime fingerprint.
• Mimics some of the real browsers' properties by injecting several JS files and using custom options.
• Custom flags are used on launch to hide Playwright even more and make it faster.
• Generates real browser headers of the same type and user OS, then appends them to the request's headers.

3. Real Chrome

DynamicFetcher.fetch('https://example.com', real_chrome=True)

If you have a Google Chrome browser installed, use this option. It's the same as the first option, but will use the Google Chrome browser you installed on your device instead of Chromium.

This will make your requests look more authentic, so it's less detectable, and you can even use the stealth=True mode with it for better results, like below:

DynamicFetcher.fetch('https://example.com', real_chrome=True, stealth=True)

If you don't have Google Chrome installed and want to use this option, you can use the command below in the terminal to install it for the library instead of installing it manually:

playwright install chrome

4. CDP Connection

DynamicFetcher.fetch('https://example.com', cdp_url='ws://localhost:9222')

Instead of launching a browser locally (Chromium/Google Chrome), you can connect to a remote browser through the Chrome DevTools Protocol.

Full list of arguments

Scrapling provides many options with this fetcher. To make it as simple as possible, we will list the options here and give examples of using most of them.

Argument	Description	Optional
url	Target url	❌
headless	Pass True to run the browser in headless/hidden (default) or False for headful/visible mode.	✔️
disable_resources	Drop requests of unnecessary resources for a speed boost. It depends, but it made requests ~25% faster in my tests for some websites. Requests dropped are of type font, image, media, beacon, object, imageset, texttrack, websocket, csp_report, and stylesheet. This can help save your proxy usage, but be cautious with this option, as it may cause some websites to never finish loading.	✔️
cookies	Set cookies for the next request.	✔️
useragent	Pass a useragent string to be used. Otherwise, the fetcher will generate and use a real Useragent of the same browser.	✔️
network_idle	Wait for the page until there are no network connections for at least 500 ms.	✔️
timeout	The timeout (milliseconds) used in all operations and waits through the page. The default is 30,000 ms (30 seconds).	✔️
wait	The time (milliseconds) the fetcher will wait after everything finishes before closing the page and returning the Response object.	✔️
page_action	Added for automation. Pass a function that takes the page object and does the necessary automation, then returns page again.	✔️
wait_selector	Wait for a specific css selector to be in a specific state.	✔️
wait_selector_state	Scrapling will wait for the given state to be fulfilled for the selector given with wait_selector. Default state is attached.	✔️
google_search	Enabled by default, Scrapling will set the referer header as if this request came from a Google search of this website's domain name.	✔️
extra_headers	A dictionary of extra headers to add to the request. The referer set by the google_search argument takes priority over the referer set here if used together.	✔️
proxy	The proxy to be used with requests. It can be a string or a dictionary with the keys 'server', 'username', and 'password' only.	✔️
hide_canvas	Add random noise to canvas operations to prevent fingerprinting.	✔️
disable_webgl	Disables WebGL and WebGL 2.0 support entirely.	✔️
stealth	Enables stealth mode; you should always check the documentation to see what the stealth mode does currently.	✔️
real_chrome	If you have a Chrome browser installed on your device, enable this, and the Fetcher will launch and use an instance of your browser.	✔️
locale	Set the locale for the browser if wanted. The default value is en-US.	✔️
cdp_url	Instead of launching a new browser instance, connect to this CDP URL to control real browsers through CDP.	✔️
selector_config	A dictionary of custom parsing arguments to be used when creating the final Selector/Response class.	✔️

Examples

It's easier to understand with examples, so let's take a look.

Resource Control

# Disable unnecessary resources
page = DynamicFetcher.fetch(
    'https://example.com',
    disable_resources=True  # Blocks fonts, images, media, etc...
)

Network Control

# Wait for network idle (Consider fetch to be finished when there are no network connections for at least 500 ms)
page = DynamicFetcher.fetch('https://example.com', network_idle=True)

# Custom timeout (in milliseconds)
page = DynamicFetcher.fetch('https://example.com', timeout=30000)  # 30 seconds

# Proxy support
page = DynamicFetcher.fetch(
    'https://example.com',
    proxy='http://username:password@host:port'  # Or it can be a dictionary with the keys 'server', 'username', and 'password' only
)

Browser Automation

This is where your knowledge about Playwright's Page API comes into play. The function you pass here takes the page object from Playwright's API, performs the desired action, and then returns it for the current fetcher to continue processing.

This function is executed immediately after waiting for network_idle (if enabled) and before waiting for the wait_selector argument, allowing it to be used for various purposes, not just automation. You can alter the page as you want.

In the example below, I used page mouse events to move the mouse wheel to scroll the page and then move the mouse.

from playwright.sync_api import Page

def scroll_page(page: Page):
    page.mouse.wheel(10, 0)
    page.mouse.move(100, 400)
    page.mouse.up()
    return page

page = DynamicFetcher.fetch(
    'https://example.com',
    page_action=scroll_page
)

Of course, if you use the async fetch version, the function must also be async.

from playwright.async_api import Page

async def scroll_page(page: Page):
   await page.mouse.wheel(10, 0)
   await page.mouse.move(100, 400)
   await page.mouse.up()
   return page

page = await DynamicFetcher.async_fetch(
    'https://example.com',
    page_action=scroll_page
)

Wait Conditions

# Wait for the selector
page = DynamicFetcher.fetch(
    'https://example.com',
    wait_selector='h1',
    wait_selector_state='visible'
)

This is the last wait the fetcher will do before returning the response (if enabled). You pass a CSS selector to the wait_selector argument, and the fetcher will wait for the state you passed in the wait_selector_state argument to be fulfilled. If you didn't pass a state, the default would be attached, which means it will wait for the element to be present in the DOM.

After that, the fetcher will check again to see if all JS files are loaded and executed (the domcontentloaded state) or continue waiting. If you have enabled network_idle with this, the fetcher will wait for network_idle to be fulfilled again, as explained above.

The states the fetcher can wait for can be any of the following (source):

• attached: Wait for an element to be present in the DOM.
• detached: Wait for an element to not be present in the DOM.
• visible: wait for an element to have a non-empty bounding box and no visibility:hidden. Note that an element without any content or with display:none has an empty bounding box and is not considered visible.
• hidden: wait for an element to be either detached from the DOM, or have an empty bounding box, or visibility:hidden. This is opposite to the 'visible' option.

Some Stealth Features

# Full stealth mode
page = DynamicFetcher.fetch(
    'https://example.com',
    stealth=True,
    hide_canvas=True,
    disable_webgl=True,
    google_search=True
)

# Custom user agent
page = DynamicFetcher.fetch(
    'https://example.com',
    useragent='Mozilla/5.0...'
)

# Set browser locale
page = DynamicFetcher.fetch(
    'https://example.com',
    locale='en-US'
)

Hence, the hide_canvas argument doesn't disable the canvas but instead hides it by adding random noise to canvas operations, preventing fingerprinting. Also, if you didn't set a user agent (preferred), the fetcher will generate a real User Agent of the same browser and use it.

The google_search argument is enabled by default, making the request look as if it came from a Google search page. So, a request for https://example.com will set the referer to https://www.google.com/search?q=example. Also, if used together, it takes priority over the referer set by the extra_headers argument.

General example

from scrapling.fetchers import DynamicFetcher

def scrape_dynamic_content():
    # Use Playwright for JavaScript content
    page = DynamicFetcher.fetch(
        'https://example.com/dynamic',
        network_idle=True,
        wait_selector='.content'
    )
    
    # Extract dynamic content
    content = page.css('.content')
    
    return {
        'title': content.css_first('h1::text'),
        'items': [
            item.text for item in content.css('.item')
        ]
    }

Session Management

To keep the browser open until you make multiple requests with the same configuration, use DynamicSession/AsyncDynamicSession classes. Those classes can accept all the arguments that the fetch function can take, which enables you to specify a config for the entire session.

from scrapling.fetchers import DynamicSession

# Create a session with default configuration
with DynamicSession(
    headless=True,
    stealth=True,
    disable_resources=True,
    real_chrome=True
) as session:
    # Make multiple requests with the same browser instance
    page1 = session.fetch('https://example1.com')
    page2 = session.fetch('https://example2.com')
    page3 = session.fetch('https://dynamic-site.com')
    
    # All requests reuse the same tab on the same browser instance

Async Session Usage

import asyncio
from scrapling.fetchers import AsyncDynamicSession

async def scrape_multiple_sites():
    async with AsyncDynamicSession(
        stealth=True,
        network_idle=True,
        timeout=30000,
        max_pages=3
    ) as session:
        # Make async requests with shared browser configuration
        pages = await asyncio.gather(
            session.fetch('https://spa-app1.com'),
            session.fetch('https://spa-app2.com'),
            session.fetch('https://dynamic-content.com')
        )
        return pages

You may have noticed the max_pages argument. This is a new argument that enables the fetcher to create a pool of Browser tabs that will be rotated automatically. Instead of waiting for one browser tab to become ready, it checks if the next tab in the pool is ready to be used and uses it. This allows for multiple websites to be fetched at the same time in the same browser, which saves a lot of resources, but most importantly, is so fast :)

When all tabs inside the pool are busy, the fetcher checks every subsecond if a tab becomes ready. If none become free within a 30-second interval, it raises a TimeoutError error. This can happen when the website you are fetching becomes unresponsive for some reason.

Session Benefits

• Browser reuse: Much faster subsequent requests by reusing the same browser instance.
• Cookie persistence: Automatic cookie and session state handling as any browser does automatically.
• Consistent fingerprint: Same browser fingerprint across all requests.
• Memory efficiency: Better resource usage compared to launching new browsers with each fetch.

When to Use

Use DynamicFetcher when:

• Need browser automation
• Want multiple browser options
• Using a real Chrome browser
• Need custom browser config
• Want flexible stealth options

If you want more stealth and control without much config, check out the StealthyFetcher.