Simply-the-best-for-you Volunteer Community Mentor
ShipScript has been an eBay Community volunteer since 2003, specializing in HTML, CSS, Scripts, Photos, Active Content, Technical Solutions, and online Seller Tools.
They are absolutey NOT sequential & they haven't been for a good 10-15 years or longer. I do think they were at the beginning, in the mid 90's, but I can't be certain, b/c my memory for that is long gone. They were shorter then, as well, IIRC it was 7 digits.
The last 3 items I listed are:
175679058391
175679032649
354699995342
In what universe are those sequential numbers? Also note, as I said in my first post, ALL your items will start with a non-unique set of 3 digits (prefix). Mine are all 175 or 354. In my testing referenced above, about 30 of us that I checked with ALL had the same pattern, though a different set of prefixes. A couple of us in that study I did, only had 1 prefix, but as you can see above, even of my last 3 items, the 2 that started with the same prefix, the numbers were not sequential.
The vast majority of us in that study had 2 prefixes, making it IMPOSSIBLE for the numbers to be sequential. Now, certainly something could have changed BUT my listings still follow this same pattern, all these years later, all 1400ish of my listings start with the same 2 prefixes.
My study was somewhat limited in that we were all clothing sellers. @inhawaii I took a quick glance at about 15 of your listings & you have a lot more prefixes than I do, which leads me to guess that they indicate something about the category the item is in, as you have a lot of categories. Mostly your listings that I checked are 191, 192, 223, 224, 195 & 221. You have these prefixes amongst multiple items. Again, making it IMPOSSIBLE for your numbers to be sequential as a whole 10 digits. It is possible that some some segment of the characters is sequential, though I don't see that at all in my last 3 item numbers posted above & for the record, all 3 of mine are women's clothes.
@zamo-zuan @wastingtime101 Just b/c I'm curious, do either of you happen to know the significance of the first 3 digits of the item #? See my post above (#31 & #15). I KNOW the item numbers are not sequential, as proven in post 31 & also proven b/c of the whole 3 digit prefix thing I described, I'm just wondering if either of you happen to know the significance of the 'prefix'? I can think of MANY different ways that Ebay could use it 😉
@inhawaii wrote:So i guess most of you are saying item numbers are not random.
If you were to take 1,000,000 item numbers and looked at the last digit,
one number would appear predominantly more than another number?
@inhawaii, interesting question. I was not going to try to get a million item numbers, but I did check a smaller number to investigate this.
In order to get a fairly random selection of eBay items, I searched for the keywords (new, used) in all categories. I wanted to include items from all categories, all locations, and all types of items. Then I pulled all the item numbers from the first 7 pages of results, and eliminated the duplicates (from sponsored items). At 240 items per page, there should have been 1680 items, but after eliminating the duplicates, I had 1601 items left.
Here is the distribution of the last digits from this experiment. The mean (average) value is 160.1, which is exactly what you would expect with 1601 item #s. The range is between 144 (for the digit 1) and 193 (for the digit 7). I would say that at least the last digit is random.
Your results may vary, if the category, or seller location, or some other factor has an influence on the last digit, as it appears may be the case for the starting digits.
@inhawaii, I did say that your mileage might vary.
I wondered what it would look like if I checked your listings, specifically. I included both your active listings, and completed ones (at least, the ones that show up in a completed items search). The results were more variable. That might be just because it's a much smaller sample, but there is a much larger range of results.
And, if you want just your active items:
Thank you @wastingtime101 , I'll take a look at those posts & look fwd to seeing if @shipscript knows anything. Just FYI, my prefix is NOT & has never been sequential. But when I looked & posted @inhawaii 's, several of his are. They mean something, but who knows what.
Very interesting @lacemaker3 , certainly some part of the number has to be unique & sequential is an easy way to do that, but sequential based on what? We don't know. It's not sequential based on your own listing. The 5 I listed last night & the 3 I posted I'd listed the day before, show that. Here's last nights.
175684145605
175684107342
354709042787
175684055795
175684039125
Note that 3 of the 5, end in the number 5. Maybe that's a coincidence, hard to know. These were listed in the wee hours of the night/morning. While I believe that some part of the number is likely sequential, it's not very clear here. I see no pattern other than the 2 prefixes I always have. Most of these were in the same category, so if it was sequential by category, I would expect some part of the character string to appear close to sequential. It's obviously not sequential by your own listings or your own listings in a category. A bit odd that 3 out of 5, end in the number 5, too, but maybe coinkydink based on Lace's experiment.
@zamo-zuan wrote:
@simply-the-best-for-you wrote:@zamo-zuan @wastingtime101 Just b/c I'm curious, do either of you happen to know the significance of the first 3 digits of the item #? See my post above (#31 & #15). I KNOW the item numbers are not sequential, as proven in post 31 & also proven b/c of the whole 3 digit prefix thing I described, I'm just wondering if either of you happen to know the significance of the 'prefix'? I can think of MANY different ways that Ebay could use it 😉
That's something I actually never did testing on.
Doing a quick export of our records with all of our listings ItemID's and creation dates I find:
270, 271, 272, 273.274,275, 280, 281, 283, 284, 285, 300, 301, 302, 303, 304
Doesn't seem linked to category. But there DOES seem to be some relation to date.
For example, 270 starts at listings created 2011, this sequentially goes through the years until 2018 at 273 and 2022 at 275.
280 is back at 2011, and same deal, listing creation date sequentially goes through the years with 285 reaching 2022 then 2023.
300 starts in 2012, with 304 reaching 2022 then 2023.
So it looks date related. Why they might choose 27x, 28x, or 30x? I've no idea. Maybe they're reusing the numbers as old listings are taken down?
@zamo-zuan Thanks, that's interesting. I only have 2 prefixes & always have. Mine are not sequential (175 & 354), as many of yours are & several of Inhawaii's are. Also, I can say with certainty (see the 5 item numbers I listed last night from my post to Wastingtime), I pretty much always get these 2 prefixes & at a glance of a report that has all my items on it, they all seem to have the same 2 numbers. I DO refresh my listings every 6-9 mos usually, so while I have items from years ago, they've all been listed more currently.
I *believe* though, that these are the same 2 prefixes I've had since the dawn of the 10 digit item number. I can't say it with 100% certainty though, since I'd have to dig deep into my old documentation on this. I started a spreadsheet at one time with about 30 people's, but IDK if I even still have that doc b/c it became too time consuming for me to complete & also b/c 'then what'? I am very curious, but knowing isn't going to change much of anything LOL. Kinda like most things about Ebay 🙂 Thanks for your input!
This link provided by @wastingtime101 summarizes my experience with item numbers.
https://developer.ebay.com/support/kb-article?KBid=468
In my early experience, eBay assigned item numbers based on category. The numbering has been sequential within those groups. When eBay went from 10 digits to 12 digits, they started moving away from the category theme of numbering. But, by then, they had already started a bunch of parallel sequences, so they will have to infill as they go forward (by working within ranges that are not already assigned to listings).
I had also found back then that, when eBay had the time, my 12-digit item numbers all had the same prefix and the same number of bot views while being scanned by eBay's filters before launching. But occasionally, like the Sunday bustle, some of my similar listings in the same batch had no bot scans and had a different prefix. That led me to believe there was an unscanned pile. My listings tended to stay within those two prefixes, as if category-specific (but more likely in the catchall category).
I have not determined if eBay uses a checksum (the last digit in the item id), but suspect they might. If so, the numbers will never be sequential to the last digit because a checksum is, roughly, the sum of all other digits, while the actual sequence would stop one short of the checksum. In any event, it would be quite rare to have sequential item numbers anyway unless someone bulk listed programmatically; and even then, eBay is a multi-threaded operation, taking in content simultaneously from many sources, so uploads could be interleaved with other seller's uploads, their numbers leap-frogging each other.
Looking at my own active listings, which date back to 10 years, my listings always led with 22 or 38, and I believe those where my two prefixes long before that. My oldest current prefixes are 222 and 380, and have grown over time to 225 and 385. You can follow the progression (start dates and item numbers) here.
But here is an example from three identical listings that were programmatically (all at once) listed over three years ago. Notice that the first two are sequential (if there is a checksum), while the third went into a different bin entirely. Since eBay no longer displays bot-views, I would not know if the third went into a no-scan group or whether that is simply a load-balancing act eBay uses to spread the number of requests that might hit the database at the same time.
223824691527 #1
223824691533 #2
383346568097 #3
@zamo-zuan, @shipscript, FYI.
@simply-the-best-for-you, there is very definitely a pattern to your item numbers. As you have noticed, the first 3 digits of your item numbers are always one of two 3-digit numbers. We have been calling that the prefix. In the chart below, I separated your two prefixes to make it easier to see the patterns within each 3-digit-prefix.
The next 9 digits are not sequential, but, they are always in order. By that I mean, they are always increasing. The second set of 3 digits, generally stays the same for each day that you list, but then the next day, this set of next-3-digits generally goes up by one (occasionally by two or three).
It doesn't always increment according to the day, though. There are several days here, where the next-3-digits went up by one in the middle of a listing session, on the same day. However, it is quite helpful to look at the next-3-digits, because that makes the pattern more visible.
When you put the next-3-digits together with the last-6 digits, the last-9-digits are always increasing with time. So, they are being assigned based on the date and time when the listing was created, and for someone who lists at your rate, that works out to approximately one day for each next-3-digits increment.
I believe that @zamo-zuan posts a lot more listings, and that would explain why their prefix has been incrementing more rapidly than @simply-the-best-for-you's prefix appears to increment. It's probably not exactly by the year the listing was created, it's just that with @zamo-zuan's rate of listing, it works out that their prefixes are incrementing by one at approximately one year intervals.
@simply-the-best-for-you's recent listings (total of 60 listings):
The 3-digit-prefixes are not unique to a seller, of course, even though they appear to stay constant. There are only 1,000 possibilities, and eBay has a lot more sellers than that. So the 3-digit-prefixes have to be reused between sellers.
I don't think that eBay is using a checksum for the last digit, because if that were the case, then occasionally the last-6-digits would not be increasing, and it appears that they are always increasing.
