Best booru to upload images to for maximum propagation?

How do all the different boorus mirror images from one another and where should I upload to post it once and have it get mirrored everywhere else?

If the image is a good image for Derpibooru
Upload it over there. Like them or not, they are still the de facto booru of record. As long as it is an image that follows their rules and doesn't get hit with a DNP, everywhere else will mirror it soon enough.
However, uploading a Derpi-safe image elsewhere won't get copied to there without manual intervention, as I do not believe they run any porter bots.

If it's not a Derpi-safe image
Ponybooru? I don't know whether they pull from here and Twibooru or if they only copy uploads from Derpi. I do know that here and Twibooru both pull from one another as well as from Ponybooru and Derpi.

OK, what's going on with the importer? I uploaded an image to Ponybooru that did not get mirrored to here or to Twibooru. However, I see that the import has been successfully run since the image was uploaded. Likewise, I also uploaded an image here that did not get mirrored to Twibooru. Should I manually spread the uploads at this point?

EDIT: it turns out that I have too many chromosomes and my Ponybooru pic did successfully make it over here. It merely got removed by my filter. However, both images have not made their way to Twibooru (and I even checked with filters off to make sure).

@𝚽σ𝜏mares

My own pic got removed by my own filter

Kek.

As for your question, I don't really know. It's been a while since I was up to date on things. I do know that Ponerpics runs it's own importer bot, but I don't have a complete list of what sites it scrapes. I'm sure someone has made some kind of multi-importer tool that can upload to all or most boorus by now.

As for your question, I don't really know. It's been a while since I was up to date on things. I do know that Ponerpics runs it's own importer bot

If it does, it almost definitely has some kind of filter on it. Not every image from the other boorus is on this site. In my personal opinion, there should be zero filters when importing because this should be the be-all end-all of the MLP boorus. It should be containing whatever is on the others, and then some. But whoever is running the importer bots are clearly filtering content for one reason or another.

@BrokenInside™

There are three blocked users in the script, sapphie (runs the Ponybooru importer, so everything here should already be imported from the other boorus) and two other users who requested to be filtered as they upload here first. I should note that these filters (with the exception of sapphie) are probably less necessary these days as the importer has dupe detection now.

Not every image from the other boorus is on this site.

It's possible that some images were imported from other boorus first, and sometimes it can be just difficult to locate some images. I know every once in a while I come across an image that will not come up with a reverse image search and takes extensive looking through tags to locate.

@porter
As a quick example I found right now, this artist artist:wapamario63 is missing 6 recent images. indigosfm is another one missing two recent posts. An applecest webm animation, and candyass
These are just two offhand quick examples. There's many others.

Is this site dead sometimes? Ocasionally it takes almost a whole day to appear new images here… Is it always like that? And do you import everything that appears on derpibooru?

@Sonork
Seems normal to me. And yes, everything.

@Sonork
Sometimes porter gets stuck on an image. Usually he notices within a few hours, but I guess he's been busy the last couple times.

If I want to import a bunch of Mercurial art that's not already shared and have it both here and on Twibooru, should I upload it here or to Twibooru?

@Background Pony #C36C
Twibooru, it'll import here