How Googlebot Renders (Roleplaying as Google's Web Rendering Service-- D&D style)

Think like a bot,
Rank like a boss:
How Googlebot renders
Jamie Alberico // Not a Robot
SLIDESHARE.NET/JAMIEALBERICO
@JAMMER_VOLTS

Jamie Alberico
My name means Usurper Elf
King.
I’m a Technical SEO, Search
Advocate, & Wood Elf Druid.
Oh yeah, and I’m Not a
Robot.
#brightonSEO @Jammer_Volts

Masters of unlocking magic in everyday
objects, Technical SEOs are extremely
resourceful.
They see magic as a complex system
waiting to be decoded and controlled.
Proﬁciencies (recommended)
Chrome Developer Tools, Lighthouse,
Google Search Console, webcrawlers
Technical SEOs
Class Details

Our Technical
SEO Quest
To protect site visibility by delivering
our content to Google’s index.
To do this, we must pass
through a powerful construct.

When Googlebot retrieves your pages,
Googlebot runs your code, and assess your
content to understand the layout or structure of
your site.
What is Rendering?

All information Google collects during the
rendering process is then used to rank the quality
and value of your site content against other sites
and what people are searching for with Google
Search.
How Google Search Works, Search Console Help Center
Rendering’s role in Rank

Initial HTML
(1st wave of indexing)
Rendered HTML
(2nd Wave of indexing)
Rendering

If Google cannot render the pages on
your site, it becomes more diﬃcult to
understand your web content because we
are missing key visual layout information
about your web pages.
As a result, the visibility of your site
content in Google Search can suffer.
Rendering Risks

Until 2018, we thought our quest looked
like this
Crawl
Index
Rank

Now, we know that Rendering is part of the process
and that Google has two waves of indexing.
Crawl Index
Render
Rank
First Wave
SecondWave

If Google can’t render content, we fail our quest
Crawl Index

Google’s Web
Rendering Service
(WRS)
Insight Check

Google Web Rendering Service
Large Construct (legendary), lawful neutral
Languages HTML, CSS, JavaScript, Images
Skills Perception +12, Dexterity +10
Senses Robots.txt, Robots directives

Takes action using threads
Each requests to made by a thread. A thread is a single
connection. It sequentially moves through each action,
one at a time, until it’s task is complete.
Features & Traits Actions Equipment

SEOs call this Crawl Budget
“Simply put, [crawl budget] represents the number of
simultaneous parallel connections Googlebot may use to
crawl the site, as well as the time it has to wait between
the fetches.”
What Crawl Budget Means for Googlebot, Google Webmaster Blog

Stateless
● Does not retain state across page loads
● Local Storage and Session Storage data are cleared
across pages loads
● HTTP Cookies are cleared across page loads

Obedient
Obeys HTML/HTML5 protocol
Literal
“Googlebot, go to the apothecary and buy a
healing potion. If they have shields, buy 2. “
Googlebot comes back with 2 potions.

Politeness is priority 0
Crawling is its main priority while making sure it doesn't
degrade the experience of users visiting the site. We call
this the "crawl rate limit," which limits the maximum
fetching rate for a given site.
What Crawl Budget Means for Googlebot, Google Webmaster Central Blog

Multi-thread
Googlebot can execute more than one request at a time
if demand and server stability allows.

Request URI
Googlebot send a request for content at a unique
resource instance (URI).
Googlebot can discover a URL
via link or submission

Read HTTP response and headers
Q. Does the thing I asked for exist?
A. HTTP Status Codes
Q. Anything I should know before looking at this?
A. Cache-Control, and Directives

Parse
Download the response from
server
Features & Traits Equipment Actions

Identify Resources
Googlebot identiﬁes resources
needed to complete the request.
It feeds identiﬁed resources into
the crawling queue.
Use Network tab to see how many
resources a page calls

Cache
If the requested website implements a cache, a copy of
the data is made or requested

Actions
WRS, web rendering service
Features & Traits Equipment
Googlebot queues pages for both crawling and rendering. It is not
immediately obvious when a page is waiting for crawling and when it is
waiting for rendering.
WRS is the name used to represent the collective elements involved in
Google’s rendering service. Many details are not publically available.

Web Rendering Service (WRS)
Blink Browser Engine
V8 Rendering Engine
Ignition TurboFan Liftoff Display backend
GoogleMagic
Chromium Headless Browser

Actions
WRS process
1. A URL is pulled from the crawl queue
2. Googlebot requests the URL and downloads the initial HTML
3. The Initial HTML is passed to the processing stage which extracts links
4. Links go back on the crawl queue
5. Once resources are crawled, the page queues for rendering

Actions
WRS process
6. When resources become available, the request moves from the render
queue to the renderer
7. Renderer passes the rendered HTML back to processing
8. Processing indexes the content
9. Extracts links from the rendered HTML to put them into the crawl
queue

Chromium, headless browser
EquipmentActionsFeatures & Traits
● Headless means that there is no GUI (visual representation)
● Used to load web pages and extract metadata
● reading from and writing to the DOM
● observing network events
● capturing screenshots
● inspecting worker scripts
● recording Chrome Traces

Blink, browser engine
● Allows for querying and manipulating the rendering
engine settings (ex: mobile vs. desktop)
● Blink loves service workers. Blink may create multiple
worker threads to run Web Workers, ServiceWorker
and Worklets

Blink is responsible for 2 major elements:
Memory heap: stores the result of script execution
(Memory Heap results are added to DOM.)
Call stack: queue of sequential next steps
(Each entry in the call stack is called a Stack Frame.)

Local storage and Session storage are key-value pairs
that can store any JS objects and functions in the
browser
These keys are a weak point in your rendering offense
against a stateless Googlebot.

V8, JavaScript engine
JavaScript is a single-threaded process and each entry or
execution step is a stack frame.
Googlebot can opt run simultaneous parallel
connections.

Each thread will runs through a process of:
1. Loading
2. Parsing
3. Compiling
4. Executing

● open-source JavaScript engine and WebAssembly
engine
● developed by Google & The Chromium Project
● Use in Node.js, Google Chrome, and Chromium web
browsers

V8’s components
● Ignition, a fast low-level register-based JavaScript
interpreter written using the backend of TurboFan
● TurboFan, one of V8’s optimizing compilers
● Liftoff, a new baseline compiler for WebAssembly

Optimized Rendering
Roll with Advantage

Parse content critical to
user intent in initial HTML

Crawl
Index
Render
HTML
DOM
1st wave of
indexing
2nd wave of
indexing

Critical = why the user came

Deﬁne it for your site, by template

Use clean, consistent signals
Googlebot won’t see past a noindex directive in initial HTML
to see an index placed in DOM.
Duplicative content without a canonical in initial HTML is
crawl waste until rendering.
Inconsistent title tags and descriptions can result from
overwriting the initial HTML with rendered HTML.

Focus rendering efforts with nofollow
If a resource is not valuable to the construction of the page,
add a nofollow directive to resources that are not necessary
or beneﬁcial to page construction.

Mobile vs Desktop Rendering
Layout matters for both.
If you want to rank for
position zero, remember that
the content must be exposed
on initial mobile load.

Choose the rendering strategy that’s
right for your business and stack.
You don’t have to be 100% client-side, 100% server-side, or
100% both (dynamic).
Load what matters when it matters.

Rendering
Challenges
Survival Check

Rendering
&
Performance
DOM
HTML
Style
Sheets
HTML
Parser
CSS
Parser
DOM
Tree
Style
Rules
Render
Tree
Attachment
Layout
Painting Display
TTFB
TTI

More Pages Resources require more
rendering resources
Each resource must be fetched independently before the
page can be accurately rendered.
This is a major part of the issue with client-side rendering.
More client-side calls mean more blindspots for you.

Excessive scripts
runs the risk of
hitting thread/rest
thresholds.
This is most often
observed as Other
error .

Call Stacks have a maximum size
While the Call Stack has functions to execute, the browser
can’t actually do anything else — it’s getting blocked.

Session and Local web storage limits
5MB per object, and 50MB per system
If your CSR resources are too large, you risk hitting the upper
limit. Elements in queue once the limit is reached may not be
considered by Googlebot.

Load scripts & images without blocking
Asynchronous calls are supported with async attributes
<rel=”myscript.js” async defer>
Lazy load images in Chrome with native attributes
<img src=”the-traveler.jpg” loading=”lazy”>

Broken Structured Data Markup

Don’t trust document.write( )
Dynamic code (such as script elements containing
document.write() calls) can add extra tokens, so the parsing
process actually modiﬁes the input.

Render Testing
Check for traps

Test local/ﬁrewalled with tunneling
SimpleHTTPServer (http.server in Python 3) is a Simple HTTP
request handler for QA

Test local or ﬁrewalled with tunneling
ngrok exposes that page on a publicly accessible URL

Make Allies

|￣￣￣￣￣￣￣￣￣￣￣|
DON'T BE AFRAID
TO LEARN IN PUBLIC
|＿＿＿＿＿＿＿＿＿＿＿|
(__/) ||
(•ㅅ•) ||
/ 　づ #brightonSEO @Jammer_Volts

Resources
● Get started with Chrome Developer
Tools
● HTML/HTML5 Parsing Standards
● Debugging your pages
● SimpleHTTPServer
● Ngrok
● Fix Search-related JavaScript
problems
● TurboFan overview
● Liftover overview
● Tame the Bots Portals
● Blink Rendering, life of a pixel
● The Rendering Critical Path
● JavaScript Sites in Search Working Group

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