Unzip Files Online — Preview & Extract ZIP Instantly
ZIP is the world's most universal archive format — created in 1989, it's natively supported on Windows, macOS, iOS, and Android. Yet sometimes you want to look inside a ZIP before extracting everything, or you're on a device where the built-in unzip tool doesn't work as expected. FastZip's online ZIP tool gives you full visibility and control.
Preview mode — see what's inside first — FastZip opens in Preview mode for ZIP files, which scans the archive directory in milliseconds and shows you a complete file listing: filenames, sizes, folder structure, and the total archive contents. No files are extracted yet. This is useful when you receive a ZIP from an unknown source and want to inspect it before opening anything on your computer.
Selective extraction — Once you've scanned the archive, you can download individual files or folders without extracting the full archive. This is particularly useful for large ZIPs where you only need one or two files: avoid downloading hundreds of megabytes to get a single config file.
Folder structure — FastZip preserves the original folder hierarchy when you extract. Files and directories appear exactly as they were when the ZIP was created. If someone zipped a project folder, you'll get that folder back intact.
ZIP64 extension — The original ZIP format has a 4 GB file size limit per entry and a 65,535 entry limit per archive. The ZIP64 extension, introduced in 2001, removes these limits. Most modern ZIP tools create ZIP64 archives automatically for large files. FastZip supports ZIP64 fully.
Password-protected ZIP — ZIP files can be encrypted using ZipCrypto (legacy, weak) or AES-256 (modern, strong). FastZip will prompt for a password if the archive is encrypted. WinZip and 7-Zip created most AES-encrypted ZIPs; Windows built-in ZIP encryption uses the weaker ZipCrypto method.
Format & Feature Reference
| Feature | ZIP (Standard) | ZIP64 |
|---|---|---|
| Max file size per entry | 4 GB | Unlimited |
| Max entries per archive | 65,535 | Unlimited |
| Max archive size (free tier) | 200 MB | 200 MB |
| Encryption | ZipCrypto / AES-256 | ZipCrypto / AES-256 |
| OS X attribute support | No | No |
| Unicode filenames | UTF-8 flag | UTF-8 flag |
| Preview before extract | Yes | Yes |
When to Use Preview Mode vs. Extract Mode
Preview mode scans only the archive's central directory (the index at the end of the file). This is instantaneous even for large ZIPs. Use preview when you want to inspect file names, check folder structure, or verify the archive contains what you expect before downloading anything.
Extract mode actually decompresses each file. Use extract when you need the file contents. FastZip gives you a one-click "Extract all" button as well as per-file download buttons so you can be selective.
The workflow most people find useful: preview first, then switch to extract mode and download only the files you need.
Unzipping on macOS Without Archive Utility Quirks
macOS Archive Utility handles most ZIPs fine, but has a few known quirks. It sometimes creates a "__MACOSX" folder containing macOS-specific metadata (resource forks) that confuses Windows users. It also refuses to open ZIPs with AES-256 encryption.
FastZip avoids all of these issues. It doesn't add any macOS metadata artifacts, handles AES-256 encryption, and gives you a clean file listing. For macOS users who regularly exchange ZIPs with Windows colleagues, FastZip is a cleaner experience.
Unzipping Large ZIP Files — Memory Considerations
Modern browsers allocate memory dynamically, but very large ZIP files (over 300 MB) can stress mobile devices. If you're on a phone or older iPad, FastZip will show a memory warning banner when your file exceeds a safe threshold — this is informational, not a block. The extraction may still succeed if your device has enough RAM.
On desktop Chrome or Firefox, ZIP files up to the 200 MB free limit extract reliably on any machine built in the last 5 years.