How do you convert FamilySearch URLs to catalog and image numbers?

Question

This question is purely a mathematical puzzle.

I'm sure that we have all noticed that consecutive images on the same film have URLs that only differ in the last few letters. It seems obvious that the URL contains an encoded but not encrypted version of the film and image numbers.

Does anyone know how to decode the film and image numbers from the URL?

 

Comments

Umm, Dirk, I don't think this is the answer you're looking for, but the "how" is the method that can derive the algorithm they used, which I wouldn't expect to be very difficult, considering that their purpose isn't to keep it secret from anyone.

I suspect that if you make a spreadsheet and throw in a bunch of data of film number, image number, and URL, the pattern should become obvious fairly quickly.

Of course, I expect that you're asking for someone who has already done that to provide the information to you, but - as for myself - I'm too lazy to do it - sorry!

Answer 1

After you have brought up the image, click on the information tab at the bottom of the page. There will be two items:

1. Catalog record
2. Citation

The citation will have the information you are looking for.

Answer 2

If there is no source citation on the image page, the only way to get the info you want is to take the film number in the upper left and the page number. Those correspond to the actual film and image that should be in a source citation. I don't know any way to decode that from the URL.