Task	Best starting tool	What to verify
Send many files as one download	Create ZIP	Folder paths, filenames and final archive size
Inspect an archive before extracting	Unzip Files	Unexpected scripts, executable files and unsafe paths
Try maximum DEFLATE compression	ZIP Compressor	Whether the contents are actually compressible
Combine archive images into a document	ZIP to PDF	Image order, unsupported entries and page orientation
Export archive images	ZIP to JPG	Image formats, transparency and filename order

Why size may not fall

JPEG, WebP, MP4, many PDFs and other ZIP files are usually compressed already. Repacking them at a stronger ZIP level may save almost nothing and can even add a small amount of overhead. Text, CSV, source code and uncompressed bitmap data usually respond better.

Extract safely

Inspect entry names before extraction, avoid replacing important folders, and treat executable or script files from an unknown sender as unsafe. A successful extraction does not prove that the contents are trustworthy. Keep the original archive until the expected files have been checked.

For reliable sharing, use clear folder names, avoid duplicate filenames in different locations unless the folder structure is important, and reopen the completed archive before sending it. This simple check catches missing files, unexpected empty folders and filename-order mistakes.