Supplemental material refers to URL+date+page snapshot
Supplemental material is not for files, not for web pages, but for specific URL+date+page snapshots.
What does that mean?
First, the supplemental material is a specific URL, not a web page or a file. For example, xxx.com and www.xxx.com are generally the same file, but are two different URLs. One of these two URLs is likely to be a normal web page, and the other is a supplemental material.
Supplemental material is a snapshot of a web page captured for a specific date, which means that even if the same URL, there may be multiple versions in the Google database, one of which is the new content captured by date A, this URL+ This particular date and page snapshot may be in a normal database. The content captured by another date B (the same URL, the older content) may be in the supplementary material database.
So the same URL has different versions in the Google database, different dates, new content may be in the main database, and old content may be in the supplemental material.
This is often the case recently, when you search for a particular sentence that actually doesn’t exist on the page, but it used to exist in previous versions. At this time, the URL of the old date version may be returned and marked as supplementary material.
The impact of supplemental materials on rankings
This problem is more complicated, and it is necessary to analyse the specific situation.
As mentioned earlier, the same URL may appear in different databases, and new versions of URLs may appear in normal primary keyword searches. But in other keyword searches, it may also appear in supplemental materials.
If your site has a lot of supplemental material, it may affect the ranking. However, if these supplements have a corresponding new URL+date+snapshot version, the impact on rankings will be small. If there is no new version of these supplements, the impact will be greater.
Supplemental material URL will not be updated
Will be updated, but the frequency of re-crawling is lower.
When the Google spider crawls the URL, the URL may be re-assigned to the primary database if the reason for making it a supplement is no longer there.
How long will the supplementary material exist?
In general, supplemental materials will continue to exist for up to a year or longer.
However, supplemental materials are not the biggest problem. If the new version of your website has been re-crawled, it doesn’t matter.
How to avoid supplemental materials
In addition to checking these reasons for your site’s supplemental material, links can help a lot.
Matt Cutts said when answering a post:
It is not necessarily a bad thing to have supplemental materials. Your situation in my opinion is just a reflection of the lack of PR and links. Your home page is already in our main database, but you don’t have many links. So I don’t think there is any problem with your website, except that our index database can only select a part of the file. If more people link to your website, I expect your web page to return to the main database.