Why some images fail to download
Short answer
Failed downloads are nearly always the site refusing the request rather than anything wrong on your machine. The four common causes are hotlink protection, which rejects requests that do not come from the site's own pages; bot protection, which answers a burst of requests with a challenge page instead of the image; images that have already been removed from the server; and Chrome's own save prompt turning a bulk download into hundreds of dialogs. Retrying handles the first, a longer delay handles the second.
Doing it by hand
Open the image in its own tab and save it from there, which sends the request the way the site expects and works for most single files.
Where that fails too, the remaining option is a screenshot — a re-encoded copy at screen resolution rather than the original file.
Where that falls apart
- There is no way to tell from the page which images will refuse until you try them.
- A tab-by-tab retry undoes the point of downloading in bulk in the first place.
- Sites that answer with a challenge page return HTTP 200, so a naive download writes an HTML file to disk with an image extension and the failure goes unnoticed.
- Screenshots lose the original resolution, the original compression and any transparency.
Doing it with ImgDown
Step 1
Press Retry
Failed images are marked in red and a Retry button appears. The retry fetches them a second way, without a referrer, which is enough to get past ordinary hotlink protection. Most failures clear on this step alone.
Step 2
Increase the delay between downloads
In Settings, raise the delay to 800ms or 1500ms and run the batch again. Bot protection reacts to bursts, so slowing the queue down is usually the difference between a challenge page and the actual images.
Step 3
Turn off Chrome's per-file save prompt
In Chrome under Settings → Downloads, switch off "Ask where to save each file". With it on, a hundred images means a hundred dialogs, and dismissing one by accident cancels that download.
Step 4
Save the last few by hand
Whatever is still red after the steps above is being refused deliberately. Open those images in a new tab and save them individually — usually a handful rather than the whole batch.
Related questions
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