When zipping helps
Text-heavy files compress well: Word documents with lots of text, spreadsheets, CSV exports, plain text and code. A zip can sometimes shrink these to a fraction of their size. Zipping is also handy for bundling many small files into one, so the recipient downloads a single item.
When it does not
Photos (JPEG, HEIC), videos (MP4, MOV), music (MP3, AAC) and most PDFs are already compressed. Zipping them typically saves a few percent at most. If your video is 400 MB, the zip will be about 400 MB too.
Downsides of zipping
The recipient has to unzip the file, which can be confusing on phones. Some company email filters block zip files entirely because they are a common way to hide malware. And password-protected zips using older encryption are weak, so use AES encryption if you rely on a zip password.
An easier option
Skip the zip and send the files as they are. On Skypost you can drop in many files at once and the recipient can download them individually or as a single ZIP that we create for them. Free files can be up to 200 MB each, with up to 500 MB in a folder.
