Compress a ZIP to 1MB

1 MB is 1,024 KB in the binary units that Windows and this tool use, or 1,000 KB in the decimal units that macOS Finder and some upload forms use.

To get a ZIP under a limit given in KB, type the target in KB, like 800kb, or open /compress-zip?target=800kb. The tool counts 1 KB as 1,024 bytes, so if a form might mean 1,000, set the target about 3% lower (for a 500 KB limit, use 485kb) and the file passes either way.

How far below 1 MB a ZIP can go depends on what's inside. A few photos or scans can usually reach a few hundred KB, since a photo can drop to roughly 30–50 KB and still be recognizable on a phone screen. Text files, video and audio aren't recompressed, so their combined size is the floor.

A ZIP file stores its contents already compressed with DEFLATE, so running it through another zipper barely helps — DEFLATE has no second pass to give. The real savings come from the contents: photos and PDFs are usually the heavy items, and unlike the ZIP container itself, they can be recompressed to a fraction of their size because their own formats have quality dials the ZIP container doesn't. A folder of 30 phone photos zipped up for email is a common case where this matters: the ZIP wrapper itself saves almost nothing over the raw files, but recompressing each JPEG inside typically cuts the total by more than half.

This tool inspects every file in the archive, splits your chosen size budget proportionally across the images and PDFs by their share of the total recompressible weight, then runs each one through a binary search on its own quality parameter — the same search a single-file image compression does, just repeated per file with a per-file budget instead of one global target. Files that are already compressed — video, audio, other archives, already-tiny text files — are copied through untouched, because recompressing an already-compressed stream either does nothing or makes it slightly larger.

If your archive is mostly video, audio, or already-compressed files, there may be very little the tool can actually shrink — the achievable size is bounded by whatever recompressible content exists, and the tool will tell you plainly if your target isn't reachable rather than silently producing an oversized file.

Archives with hundreds of files, or very large individual images, take longer because each recompressible file runs its own binary search independently — the total work scales with the number of images and PDFs, not just the archive's total size.

Password-protected ZIPs and split/multi-volume archives (.zip.001, .z01) aren't supported — this tool works on a single, complete, unencrypted ZIP.