Simon Willison’s Weblog

There's been quite a bit of discussion on the topic. The closest to an official answer is this non-answer from GoogleGuy, and there's a similar non-answer on one of Google's Help pages. There's an article about it here and a thread here. Many more threads at WebMasterWorld, but they're behind a subscribers-only wall.

Three popular theories:

1. Google has reached some sort of maximum key size in their database, and the supplemental results are a separate database they started to kludge around the issue. (Unlikely. I think Google's management of one of the world's largest computing networks probably includes the ability to use n-length keys.)
2. The supplemental results are "orphaned pages", or pages that would normally be dropped from the index because they don't show any (or a minimum number of) backlinks.
3. The supplemental results were spidered recently and haven't been added to the real index yet.

I think it's likely #2 or #3, but it's anyone's guess and Google is definitely not telling us the whole story.

Michael Moncur - 13th May 2004 08:04 - #

There's a good writeup by Danny Sullivan here at Search Engine Watch. In it, he mentions: What are supplemental results? At the same time Google posted new size figures, it also unveiled a new, separate index of pages that it will query if it fails to find good matches within its main web index.

Mike P. - 13th May 2004 08:26 - #

From the few examples I came across, they look to be things that they thought were dynamic: scraped search results, database dumps, the sort of stuff that had your search terms at the moment they crawled it, but they had some reason to believe it wouldn't always. But that's guessing from a pretty small sample. I need some userContent.css to make them a little more obvious in SERPs, to see enough to tell.

Phil Ringnalda - 13th May 2004 08:41 - #

In Dutch it is "Toegevoegde zoekresultaten", which is similar to "Added results" in English.

Anne - 13th May 2004 09:23 - #

Google maintain a database that comes to result only if there is nothing else for that search... those pages appears as supplemental results which are available and stored in a special side index on google.

WALEG - 13th May 2004 12:54 - #

small sample. I need some userContent.css to make them a little more obvious in SERPs

qq,qq - 13th May 2004 14:14 - #

what's the point? apart from reaching the limit for their database, why doesn't google just merge the supplemental results into the main database?

wackomenace - 15th May 2004 18:57 - #

From my own experience, Supplimental Results are usually pages which no longer exist at the returned URL, but which would have matched your search. I am still mystified at the point of bringing up non-existent pages, but perhaps it's so you can check the cached copy?

Alden Bates - 26th May 2004 02:20 - #

Two months ago Google "lost" most of the 150 pages of my site and only showed 20 or so (plus 10 old html pages which I deleted more than 6 months ago when I was sure Google had indexed their new php alternatives). In the last few days 20 of the lost php pages reappeared in Google, all without description but marked as "Supplemental Results". However, some of the old html pages are shown, with description and marked as "Supplemental Results".

Paul Brems - 3rd June 2004 08:58 - #

This is an attempt by Google and others to do away with just a fresh reindex every month. In other words from now on if you put anything on the internet it will stay there forever as a cache no matter what. I guess this allows Google to claim more search results but also makes the internet more permanent making people more responsible for their content by forcing them to realize that whatever you post online will remain there forever (along with the monthly new addition of pages). I believe this is Google's attempt to enter into the archive business like internet archive has done. After testing they will probably make the data like Google Groups that way they can incorperate adsense ads into these expired pages. I am not sure of the legality of this though because if you don't want your pages listed in Google or Yahoo anymore it is preety difficult to remove them.

Sergey - 4th June 2004 05:50 - #

I run a couple of websited and what I see is that deleted pages from a server shift from the main index to the the supplemental result's database, but also the newest pages. So, I think and I hope that The supplemental result is like a temp database where google can remove old links but also verify new pages before adding them to the main index. But if the newest pages get stuck in the supplemental result, this would mean that there are problems with those pages, then a lot of SEO won't get some good night of sleep anytime soon!

Fred - 10th November 2004 00:43 - #

I want to remove my supplement pages.

Rupesh Kumbhat - 26th December 2004 16:21 - #

I have a new site which wa sjust indexed but in the "Supplemental Results". My theory is that since these pages have very few backlinks (if any) that they have been placed in the "supplemental" database. My question is; once these pages accumulate backlinks will the results automatically move to the main index? Does anyone have expereince with this?

Jeff - 15th September 2005 17:21 - #

At the time of writing, 1st of February 2006, all 23,000 pages on our site were listed as "supplemental results". They appeared in the index in August 2005, so that's 5 months. It is a database driven ecommerce site. Our pages do appear in searches, but usually only on the last page!

I think it is a way for Google to "test out" your site and make sure it is not a scraper or spam site (which ours certainly isn't!). We are hoping to have the site added to the main index soon, as the Googlebot has been very busy on the site lately!

Frank - 1st February 2006 03:34 - #

Its making their search engine inaccurate. A lot of the supplemental results no longer exist, or need to be updated, and continue to show results that no longer exist. It is a strike against their site, I will continue to use Yahoo, as I just can't understand the point of keeping old, outdated information. I think Yahoo does a better job of this particular aspect.

John - 8th February 2006 01:43 - #

What the hell... Google is RETARDED... We finally had our 4 years old long-removed content removed from Google beginning of 2006 and now it's back as Supplemental and the CACHE's are back also.... wtf. don't they delete the caches when they remove them?

X - 8th May 2006 17:51 - #

I run about 10 sites - and they were all showing up in the main Google index, having been listed through their sitemaps system. One day my server had 2 days time during which google tried to crawl me. Since then all but 2 of my sites have been resigned to the supplemental index and havent been crawled at all. However since removing my sites from sitemaps I've noticed im being crawled again! So am hoping I'll be promoted to the main index again. Jon

Jon Benn - 9th July 2006 12:30 - #

My site is farily new, and for a long time I only had a few pages indexed, but now I have a lot more showing up in Googles indexed but most of them are supplemental results, to me it seems like Google is trying to get them in to the real index.

Anthony Elias - 20th August 2006 07:10 - #

Im having the same problem with http//hghlook.com, i still don't get what supplemtal means 100%. Im going to Dp to get more info.

ed - 11th October 2006 18:51 - #