Compress Many Images to a Maximum File Size

A single maximum size in KB applies to every file in the batch, but the work behind it is separate for each one. A flat product photo might barely need a quality drop to fit; a busy landscape at the same pixel size can need to go much further — Resizo runs the search per file rather than picking one setting for the whole batch.

The row for each file shows the limit it was measured against and whether it landed under it, so a batch of twenty never hides the one file that struggled.

A file that is already at or under the limit is not re-encoded at all — it comes back at its own size with only its metadata removed, because running it through the encoder again could only make it larger or worse, never smaller.

Preserve dimensions never touches a pixel — it only turns quality down, and a file that still cannot fit at its full size is reported as such rather than shrunk behind your back. Fit under limit tries quality first and, if that alone is not enough, reduces the picture itself a step at a time, in the same shape, until it fits or hits the smallest size Resizo allows.

Neither mode ever converts a file to a different format to hit the number — only the two levers named above are ever used.

JPEG and WebP both have a quality dial, so Preserve dimensions can usually find a setting under most limits. PNG is lossless — it stores every pixel exactly and has no quality to trade away — so under Preserve dimensions a PNG either already fits or it does not, with nothing in between for the tool to adjust.

Fit under limit is the only mode that can still help a PNG: shrinking the picture is the one lever a lossless format leaves.

Every file keeps the format it arrived in — a JPEG stays a JPEG, a PNG stays a PNG, a WebP stays a WebP — because converting formats to chase a size was never asked for. A PNG or WebP with transparent pixels keeps them; a JPEG, which cannot represent transparency at all, is unaffected either way.

A 4000×3000 photo asked to fit under 20 KB is not a quality problem — it is a pixel-count problem, and no amount of turning the quality dial down reaches a target that small at that size. Preserve dimensions reports this plainly rather than handing back a file that is technically under the limit but reduced to an unusable smear of blocks.

Fit under limit is built for exactly this case: it lowers quality to a sensible floor first, then reduces the picture’s dimensions until the number is reachable, and says in the result that it did.

Every file in the batch is decoded, measured and re-encoded by code this page hands to your own browser, so nothing is uploaded and there is no copy of it sitting anywhere else for this to work. The ZIP, when you ask for one, is also built on your device from the files already sitting in its memory.

Up to 20 images or 80 MB total, whichever is reached first, can go into one batch. A folder works the same way as a multi-file pick, and Resizo counts what it found before adding anything, so you are told the moment it can hold no more rather than after the fact.

Real files from a measured run, each held to the same limit and reaching it on its own terms.

Before

After

1. Choose your images. Drop up to 20 JPEG, PNG or WebP files onto the panel, or press Choose images. A whole folder works the same way, wherever the browser allows picking one.
2. Set one maximum size. Pick a preset chip from 50 KB to 1 MB, or type a custom limit in kilobytes. Every file in the batch is measured against this same number.
3. Choose what happens if a file can’t get there. Preserve dimensions keeps every pixel and only lowers quality, reporting a file that still cannot fit; Fit under limit lowers quality first, then shrinks the picture itself.
4. Press Compress and download. Watch each file settle as it finishes, then download results one at a time or together as a ZIP — a file that missed the limit says why, right beside the ones that made it.