What a ZIP file actually is
A ZIP is a single file that holds many other files, each stored with its name, its relative path and usually a compressed copy of its contents. That is why one archive can rebuild a whole folder tree, and why the archive is often — though not always — smaller than the sum of its parts.
Extracting does not consume the archive. It writes copies of the contents somewhere on your device and leaves the .zip intact, which is why you can extract the same archive twice and get two copies. It also means a half-finished extraction leaves you with some files and no warning that the rest are missing.
ZIP is the format nearly everything sends, and every current operating system reads it. The archives that cause trouble are the ones that are not really ZIPs — RAR and 7z files, or ZIPs that were encrypted with a password — and those are worth identifying early rather than fighting with the wrong tool.
Open a ZIP in your browser and pick out single files
Open Unzip and drop the archive in. It reads the archive in your browser and lists the contents, so you can see what is inside before anything is written to your device. Nothing is uploaded — the archive is never sent to a server, which matters when it contains documents you did not create.
From the list you can download individual files instead of the whole set. This is the main reason to use a browser tool over your operating system: when a colleague sends a 60-file archive and you need one invoice, extracting all of it just to find that invoice leaves you with 59 files to clean up afterwards.
The extracted files land wherever your browser puts downloads, which is a different place from the archive. If you pull out several files, check that folder rather than assuming they appeared next to the .zip. Need to go the other way and build an archive? Zipping a folder covers the reverse trip.
Extract a ZIP on Windows and Mac
On Windows, double-clicking a ZIP opens a preview window that looks like an ordinary folder. That view is misleading in one important way: you are looking inside the archive, not at extracted files. Running a program or saving edits from that preview often fails in confusing ways. Use the Extract All action and choose a destination first — Microsoft documents both behaviours.
On a Mac, double-clicking a ZIP extracts it immediately, creating a folder beside the archive. There is no preview step. Apple’s Finder guide describes this and the naming it uses when a folder of that name already exists — it adds a number rather than overwriting, so repeated extractions quietly accumulate.
Both built-in tools extract everything at once and will ask for a password if the archive is encrypted. Neither lets you pull out a single file without extracting the rest, and neither shows you the contents before committing. That is the trade-off against a browser tool.
Open a ZIP on a phone or tablet
On iPhone and iPad, save the attachment to the Files app, then tap the archive. iOS extracts it into a folder in the same location. The step people miss is the first one: tapping a ZIP inside Mail may only preview it, so save it to Files first and work from there.
On Android, the Files app — or your device maker’s file manager — can extract a ZIP from the Downloads folder. The wording varies between manufacturers, but the action is built in and no app purchase is required. If your file manager lacks it, a mobile browser running Unzip is a reliable fallback that needs no installation.
Phones are where archive size starts to matter. A large archive has to be held in memory while it is read, and a browser tab on a phone has far less headroom than a desktop. If an extraction stalls on mobile, that is usually the reason — move it to a computer rather than retrying repeatedly.
Archives that will not open
Two limits are worth knowing before you blame your tools. Password-protected archives cannot be opened in the browser at all: the contents are encrypted, and no amount of retrying changes that. Open those with your operating system’s archive tool and the password, or ask the sender for an unprotected copy if you are entitled to one.
Exotic formats are the other case. A .rar or .7z file is not a ZIP, and renaming it will not make it one — the internal structure is different, so the extension is just a label. Those need the matching application, or a new archive from the sender in ZIP format, which is a reasonable thing to request.
If the archive is a genuine, unprotected ZIP and still fails, the likeliest cause is an incomplete download rather than a broken format. The ZIP troubleshooting guide walks through confirming that, checking the real file type and deciding when to ask for a replacement.
Check the extracted files before relying on them
Count what came out. Compare the number of extracted files against the list the archive showed you, and look inside the subfolders rather than only the top level. A partial extraction is easy to miss when the first few files are the ones you expected.
Open at least one file of each type you plan to use. An archive can extract perfectly while containing the wrong version of a document, or a PDF that will not open for reasons of its own. If a document inside refuses to open, that is a separate problem from the archive — the PDF won’t open guide covers diagnosing it.
Keep the original .zip until you have finished working with the contents. It is your fallback if an extracted file is accidentally overwritten or edited, and it is the thing to re-send to support or a colleague if something is missing. Delete it once the work is done, not at the moment of extraction.
Open UnzipList what is inside an archive and pull out just the files you need.
Open Unzip →Frequently asked questions
Do I need WinZip or WinRAR to open a ZIP file?
No. Windows, macOS, iOS and Android all open standard ZIP files without extra software, and a browser-based tool can extract one without installing anything.
Can I open a password-protected ZIP in the browser?
No. Encrypted archives cannot be opened in the browser. Use your computer’s built-in archive tool with the password, or ask the sender for an unprotected copy.
Why is the extracted folder bigger than the ZIP file?
That is normal. Compression is reversed on extraction, so the files return to their original sizes. The ZIP is the compressed container, not the contents.