Archives

Which tool for which job

Archives do two jobs: they bundle many files into one, and they open bundles other people send you. Both directions are covered:

• Send a set of files as one attachment or upload: Create ZIP, with optional AES-256 password protection.
• Open a ZIP, RAR, 7z, TAR or ISO someone sent you: Unzip online, which lists the contents and lets you download single files or a selection.
• A strong password for a protected archive: Password generator.
• Files too heavy even after zipping: shrink them first with Compress JPG, Compress PDF or Compress video. ZIP barely touches media that is already compressed.

Many other tools here also hand you a ZIP: batch results from the image converters, Split PDF with several parts and PDF to JPG for multi-page documents all download as one archive.

The formats you will meet

• ZIP (1989) is the one archive every desktop and phone opens without extra software. Each file is stored as a separate entry with its own name, date and compression, plus a directory at the end, which is why one file can be read without unpacking the rest.
• RAR is a proprietary format popular for large downloads and multi-volume sets. RAR4 and RAR5 can both be read here.
• 7z uses LZMA2 compression and is typically 10 to 30% smaller than ZIP on text and code, with AES-256 encryption.
• TAR only bundles files; the .gz, .bz2 and .xz variants compress the bundle. It is the standard for source code, server backups and Linux software.
• ISO is a disc image. You can pull single files out without burning or mounting it.
• CAB is Microsoft's cabinet format, found inside installers and driver packages.

Office files such as DOCX, XLSX and PPTX are ZIP archives themselves, which is why zipping them saves almost nothing.

What compression can and cannot do

ZIP compresses with Deflate, the algorithm behind PNG and gzip. Create ZIP offers three levels:

• None stores files as they are. Use it when you only need one file instead of many.
• Normal is Deflate level 6, the usual balance of speed and size.
• Maximum is level 9. On text it typically saves only a few percent more than Normal and takes noticeably longer.

The level only matters for files that can shrink. JPG, PNG, WebP, HEIC, MP4, MOV, MP3, M4A, FLAC, PDF, other archives and Office files are always stored without recompression, because Deflate would cost time and save next to nothing. What does shrink: plain text, CSV, logs, JSON, XML, source code, SVG, BMP, TIFF and WAV. A 50 MB CSV export often packs into 5 to 10 MB.

Everything happens in your browser

Neither archive tool uploads anything, and neither has a server path or a daily limit. That makes them suitable for contracts, payroll exports or source code that should not pass through anyone else's servers.

Create ZIP assembles the archive in the page and keeps it in memory until you download it. Each file can be up to 2 GB, files keep their last-modified dates, and a duplicate name becomes photo (2).jpg instead of overwriting the first.

Unzip online runs libarchive, the library behind tar on macOS and BSD, compiled to WebAssembly in a background worker. Archives up to 1 GB are accepted. Every entry is listed with its uncompressed size; download one file directly, or tick several and get them as a single ZIP that keeps the folder structure.

The real limit is your device's memory. On a phone or tablet, a 700 MB archive or a very large selection to pack may exceed what the browser allows.

Passwords and what they hide

A protected ZIP encrypts every entry with AES-256 in the WinZip AES format. The old ZipCrypto method, which falls to known-plaintext attacks, is never used. Two points matter before you rely on it:

• File names are not encrypted. Anyone can list names, sizes and dates without the password. If passport-scan.jpg itself is sensitive, rename the files, or put them into an unprotected ZIP first and then protect that single file.
• The password is the whole defence. Eight lowercase letters fall quickly to a dictionary attack; 14 or more random characters do not. Send the password through a different channel from the archive.

AES-encrypted ZIPs open in 7-Zip, WinRAR, PeaZip, Keka and recent Windows 11 builds. Older built-in extractors may refuse them.

When opening a protected archive, the password field appears automatically. The password is checked on the first file you extract, and there is no recovery or guessing option for a forgotten one.

Workflows that chain well

1. Scans for an accountant: compress heavy PDFs, pack them with Create ZIP, protect the archive with a password from the password generator, and send the password by text message.
2. One document out of a big backup: open it in Unzip online and download only that file, without unpacking the rest.
3. A RAR on a locked-down work laptop: extract the files you need here, then repack them with Create ZIP if a colleague needs them in a universal format.

When something goes wrong

• "Could not open this archive." Usually an interrupted download. Compare the size with what the sender expected and download it again.
• Split archives such as .part1.rar, .z01 or .7z.001 cannot be opened, because each part is only a fragment. Join them with a desktop archiver.
• A correct password is rejected. Passwords are case-sensitive, and copying from an email often brings a trailing space.
• File names look garbled. Old Windows ZIPs in non-Latin languages may use a legacy code page for names. The contents are intact.
• Building or extracting stops on a phone. Split the files into two or three archives, or extract fewer files at a time.