404 Checker: Validate Image Links With HEAD

Nothing wastes a bulk download like a list half-full of dead links. The batch stalls, errors pile up, and you are left guessing which URLs actually worked. The 404 checker in Bulk Image Downloader From URL List heads that off by testing every URL first, using a request method built for exactly this kind of quick validation.

Why HEAD requests, not full downloads

A normal GET request pulls the entire image down. To check whether a thousand URLs are alive, that would be slow and wasteful. A HEAD request asks the server only for the response headers, no body, so it returns in a fraction of the time and bandwidth. The 404 checker fires these fast HEAD requests at your list and reads what comes back: the status code, and whether the content type is actually an image. That second check matters, because a URL can return a 200 status while serving an HTML error page instead of a picture.

Reachable versus unreachable

The checker sorts your URLs into two clear buckets:

Reachable — the URL responds and serves a valid image MIME type.
Unreachable — a 404, a timeout, or a response that is not an image at all.

That distinction is more useful than a raw status dump. You do not just want to know what returned 404; you want to know what will actually download as a usable image, which is what the MIME check confirms. A link can be technically alive yet useless, and this catches that case.

Turning the 404 checker result into a clean list

Finding the dead links is only half the value. Once the scan finishes, you can copy or download the clean list of reachable URLs and re-import it as your task. Now the download runs against only the URLs that will succeed, no stalls and no error noise. It is the difference between feeding the queue a verified list and feeding it hope. For a recurring source, run the 404 checker each time before you download and the batch stays predictable.

Where it fits your workflow

Run the checker after scraping, or after importing a URL list someone handed you, especially if the list is old or came from a site that prunes media often. It pairs naturally with the Redirect Checker, which follows 301/302 hops and shows the final destination, so between the two you can confirm both that a link is alive and that it points where you expect. It also complements the Perceptual Duplicate Finder: clear the dead links first, then dedupe what remains. Everything runs client-side in your browser; the checker only sends lightweight requests, not your data anywhere.

One habit worth adopting: treat the checker as a gate, not an afterthought. Scrape or import, run the check, re-import only the reachable URLs, then download. Done in that order, you never watch a queue grind through links that were never going to resolve, and your error log stays empty enough to actually be useful when a real problem appears.

A few seconds of validation saves a frustrating, half-broken batch later. Add it from the Chrome Web Store and let the 404 checker clear the dead URLs before your download ever starts.