Unzip and create ZIP files

1. 01Pick a tab: open a ZIP file or create a new one.
2. 02To open: choose or drag a file, search the contents, save single files or all ticked files.
3. 03To create: choose files or a whole folder, set the name and compression, tap “Create ZIP”.

What is read when opening. This tool reads the two usual packing methods: “Stored” (not compressed at all) and “Deflate” (the most common). Other methods such as BZIP2, LZMA or Deflate64, and any encryption (password-protected ZIP files), it cannot open, and it says so for the file concerned. For every unpacked file the checksum (CRC-32) from the archive is recalculated. If it differs, the row says so. The file still comes out, you just know that something is wrong with it.

Names in the ZIP. If a file has a name like “../../file” or a drive letter, that is made safe: the name you get is always inside the folder you choose, never outside. The row says whether a name looked like that.

Zip bombs. Some ZIP files are built on purpose so that a tiny file becomes huge when unpacked. A conspicuous ratio between packed and unpacked size is shown before unpacking. In addition, this tool keeps counting while it unpacks and stops as soon as more than 2 GB in total would come out, even if the archive itself claims something else.

Preview. For images and plain text this tool shows a preview, straight from the unpacked data: text only up to 1 MB, everything else you download to look at it. A preview is never run as a web page, not even for a file ending in “.html”.

“Save selected” and “Save all as ZIP”. Both unpack the files concerned and pack them again into a new ZIP file without the folder level: all files sit on one level in it, and equal names from different folders get a number added. If you want to keep the folder structure, save the files one by one.

When creating a ZIP. A whole folder (via “Choose a folder” or by dragging) keeps its subfolders. Images, videos, music, PDFs, Office files and archives that are already compressed are only stored, everything else is compressed with Deflate, which often saves a lot of space for text, spreadsheets and program code. “None” stores everything uncompressed, which is faster, but the file gets larger. At most 1 GB in total is allowed. For more you need a program of your own.

Limits. ZIP files over 4 GB or with more than 65,535 entries (the ZIP64 format) are read, but this tool does not create archives that large itself. The limit of 1 GB is far below that anyway. Very many entries (several thousand) make the list hard to survey, but not wrong.