Compressing one image is trivial. Compressing forty is where things go wrong: two files called
image.jpg from different folders, a format change that requires a new extension, and a
download folder full of results with no obvious link back to their originals.
The naming rules that prevent the mess
- Names are preserved, not invented. A file called
living-room.jpgcomes back asliving-room.jpg, so you can find it without opening it. - Duplicates are made unique. If two files in one batch share a name, the second
becomes
living-room-2.jpgrather than overwriting the first or hitting the same download name. - The extension follows the format. Compressing to WebP gives
.webpeven if the source was.jpg, because a file whose name disagrees with its contents is a file that fails to open.
Per-file results, not just a total
A batch that reports only a combined saving hides the file that got larger. The results panel lists every file separately with its own original size, compressed size and download button, so the one result that is not worth keeping is visible instead of averaged away.
This matters more than it sounds. Files that are already heavily compressed can come out slightly larger after a second pass, and the honest response is to keep the original for those.
A workflow that holds up
- Copy the files into a fresh folder first. Never batch-compress the only copy.
- Add them all at once, and check the count in the queue matches what you expected.
- Set the format and quality once, then compress.
- Read the per-file list before downloading. Remove any result that grew.
- Download, then compare the folder contents against the original list.
If a file fails
The queue marks the file that failed and says why: a format the browser cannot decode, an animated file, or one over the size limit. Other files in the batch are unaffected, which is the point of doing the work per file rather than as one operation.
When to split the batch
Images that are already small do not need the same settings as large ones. If a batch contains both, run it twice - once for the large files with a resize limit, once for the small ones with none. It takes an extra minute and produces better results than one setting applied to everything.
Try it
The compressor takes a whole batch, keeps the names straight and shows per-file results. Compressing images for email applies the same approach when the destination is a message rather than a website.