What does Second Wave Indexing mean in SEO?
Second Wave Indexing is how search engines cope with websites which are difficult to read. What exactly is it and are you holding back your Search Engine Optimizing because your website demands it?
To understand Second Wave Indexing first you need to understand how your device shows you a page on a website. So ....
- You decide to open howtoseo.link2light.com
- Your browser requests the source code of that web page from my hosting company and reads it line by line
- Early on in the code it will come across a reference to another file (the CSS file) so it will request this from the server. The CSS file defines what things should look like. How big the text should be, what should be the background colors of various areas on the page, how wide certain elements should be, etc., etc., etc. There might be multiple CSS files that it needs to request.
- Your browser puts all these things together and then shows you the page.
Google's crawler robot wanders around the web searching for new websites it doesn't know about or collecting changes that have occurred on the ones it already has in its database. The crawler doesn't open the website in the same way as you do.
Here's how it works:
- Later, and this could mean days, weeks or months, Google then looks at the page as a human would -i.e. it renders the page with reference to all the external files taken into account.
The first step is often referred to as Headless Browsing
because the robot is ignoring a lot of information in the Header area of the website code. In reality there are plenty of other places on the page which can be affected so don't take that term too literally.
The rendering which happens later is referred to as a Second Wave Indexing
. It is looking to see if the first crawl missed anything which can only be seen when external files are loaded and the page is fully rendered as it would be on a browser in front of a person.
Second Wave Indexing has a fundamental impact on SEO because if you are not showing all your content in the basic source code Google isn't going to rank you anywhere until it has done its full rendering. If links to other parts of your website are only displayed after full rendering Google will only become aware of these once it does its full render which means it can take months for it to discover all your pages.
In fact sometimes it never does because at some point it will go back to the first page it discovered and start over (just to check nothing has changed). It won't keep going deeper and wider because Google has a crawl budget for each domain - a finite amount of resource it can spend on your website. The quieter your site, the smaller the crawl budget.
- You decide to open samplewebsite.com
- Your browser requests the source code of that web page from the hosting company and reads the source code line by line.
- Have comprehensive content in the basic code which then gets replaced depending on the users screen size - this way the crawler always see at least one version of the content.
To see if your website is hiding anything from Google open the site, find a blank space, right hand click and select 'View Source'. It might be something slightly different to 'View Source' depending on the browser but it should be quite obvious.
If you want to see an example of the issue look at the source code of https://growth.org/discuss/should-neil-patel-take-down-this-ad-is-it-sexist-downright-offensive
None of the main content or the hundreds of comments can be seen in the source code. Only when a search engine carried out their second wave indexing will they get some idea what the page is about.
Second Wave Indexing is a way search engines make sure they get all of a websites content but it takes time. If you can't see your key content in the source code then your site needs second wave indexing which means its going to take longer for your work to appear in the search results - and longer for updates to be seen