I'm not sure what the cause is, but you can always try to clear the browser cache.

Steam > Settings > Web Browser > Delete Web Browser Cache

It could also be a connection problem. See if you are able to upload anywhere else on Steam (e.g. Changing profile picture)

I can upload just fine elsewhere, and I've already tried the usual jubilee of clearing caches, logging out and in, restarting my computer, etc.

Have you figured it out?
If not, what browser do you use?

I tried Chrome and Firefox - both still don't work. I eventually got the Steam Client to work, but only one image at a time, and I had to click through a dozen folders to get back to my screenshot directory.

Uploading all the images for one guide took me over 4 hours.

引用自 Vanessa：

I tried Chrome and Firefox - both still don't work. I eventually got the Steam Client to work, but only one image at a time, and I had to click through a dozen folders to get back to my screenshot directory.

Uploading all the images for one guide took me over 4 hours.

Does your chrome want to stop the uploading? (there would be something in the far right search bar that pops up when you try to upload a piucture) I had this problem and I think it was related to an addon to make sure you only join a https link.

引用自 Supper：

引用自 Vanessa：

I tried Chrome and Firefox - both still don't work. I eventually got the Steam Client to work, but only one image at a time, and I had to click through a dozen folders to get back to my screenshot directory.

Uploading all the images for one guide took me over 4 hours.

Does your chrome want to stop the uploading? (there would be something in the far right search bar that pops up when you try to upload a piucture) I had this problem and I think it was related to an addon to make sure you only join a https link.

Nope, it just uploaded forever. I do have the HTTPS everywhere addon, but my Firefox was completely unaltered and had the same issue.

引用自 ᴹ ᴼ ᴼ ᴺ C A T：

引用自 Vanessa：

I tried Chrome and Firefox - both still don't work. I eventually got the Steam Client to work, but only one image at a time, and I had to click through a dozen folders to get back to my screenshot directory.

Uploading all the images for one guide took me over 4 hours.

Probably a router or firewall setting. I can't do this at work.

If it happens again, create a wifi hotspot using your mobile phone. This always does the trick for me.

I don't own a mobile phone, unfortunately.

Have you tryed to check if you get that error on chrome?
It sould be a little sheild that tells you that the website wants to do something that could cause harm, which would be taking photos from your pc.

Just an idea, perhaps something is wrong with the picture?
Too large? Bad format? Bad resolution? Disallowed filename?

引用自 ZanyScum：

Just an idea, perhaps something is wrong with the picture?
Too large? Bad format? Bad resolution? Disallowed filename?

As I said in the original post, no. They were .png files, under 2MB, that uploaded perfectly fine before, and literally no image, not even ~1k/b jpegs were uploading on chrome or firefox.

Perhaps your personal capacity for uploads is reached?
I don't what it is.
I reached it years ago, then one day, months or years later, don't know, I could upload again because they increased the available space.

I am having the same issue on Chrome. And I checked I am not out of Steam Storage. Any suggestions?

Yeah I don't know what's going on but I was able to upload images fine (all under 2MB PNGs/JPGs) and ever since yesterday I can't upload new images to my workshop item.

I've tried Firefox/Chrome on my work computer and home computer as well as the client at home and on my phone and Chrome on my phone. They all just spin forever. Incredibly frustrating.

The servers are having issues since yesterdays updates.

Oh man, thank you that takes a load off my mind. This was driving me up a wall.

It should get better soon. Just try again and every hour or so.