Zip tools

Archives are the one file operation where sending your data to a server is hardest to justify. Putting ten files into one container involves no analysis and no conversion — it is pure bookkeeping, and a browser can do all of it. This page covers what is here now, plus the four things about ZIP that catch people out.

What ZIP is, and why it outlasted everything else

ZIP was published by PKWARE in 1989 and has changed remarkably little since. Its compression method, deflate, was deliberately released without patent restrictions, which is why it ended up inside PNG, HTTP responses, PDF and countless other formats rather than staying a product feature.

That decision is the whole reason ZIP is the default today. Windows Explorer, macOS Finder, the iOS Files app, Android file managers, every Linux desktop and every programming language can read a ZIP with nothing installed. Formats with better compression ratios exist and have existed for decades; none of them can claim that.

So the practical rule for sending files to someone whose setup you do not know is simple: use ZIP. You lose a few per cent of compression and gain the certainty that they can open it.

How to open a ZIP without installing anything

People search for an online ZIP extractor far more often than they need one, so here is the honest answer first. On Windows, right-click the file and choose Extract All — this has been built in since Windows XP. On macOS, double-click it; the Archive Utility unpacks it beside the original. On iOS, tap it in the Files app. On Android, most built-in file managers handle it, and Google Files does.

An online extractor is worth reaching for in two situations: the archive is on a machine where you cannot install software and the built-in handler is failing, or the archive uses something the operating system does not support — 7z, RAR, or a ZIP with AES encryption. In the far more common case of an ordinary ZIP, uploading it somewhere is slower and less private than the tool already on your device.

If double-clicking gives an error, the usual causes are an incomplete download (compare the file size against the source), an archive that is actually 7z or RAR with a .zip extension, or a password-protected archive whose password you were not given.

ZIP, 7z, RAR or tar.gz — how to choose

ZIP for anything leaving your control. Maximum compatibility, adequate compression, no software required at either end.

7z when the ratio genuinely matters — large text corpora, disk images, source trees. Its LZMA compression is substantially better than deflate, and it is free and open, but the recipient needs 7-Zip or an equivalent installed. Sending 7z to a non-technical recipient reliably produces a confused email.

RAR is worth knowing about mainly because you will receive it. The format is proprietary: extraction is broadly supported but creating one requires licensed software, so it is not a format to standardise on.

tar.gz and tar.zst are the Unix convention and the right choice for anything involving file permissions, symbolic links, or deployment to a server, because tar preserves that metadata and ZIP largely does not. On Windows they are awkward without extra software.

The two things that go wrong with ZIP files

Filenames turning into rubbish is the first, and it is a design gap rather than anybody's bug. The original specification never said which character encoding filenames use, so tools wrote the machine's local code page — Big5 in Taiwan, GBK in mainland China, Shift_JIS in Japan. A flag for declaring UTF-8 was added much later. When an archive written with one assumption is read with another, every non-ASCII character becomes noise. Modern tools write UTF-8; very old Windows extractors do not read it. Nothing the person creating the archive does can fix a reader that guesses wrong, which is why ASCII filenames remain the only guarantee for unknown recipients.

Password protection is the second, and it is worse than most people assume. ZIP's original encryption, ZipCrypto, has known plaintext attacks and is cracked in seconds by freely available tools. The strong replacement, AES-256, is a vendor extension that Windows Explorer cannot open at all — so a "password-protected ZIP" is either insecure or unopenable by your recipient's built-in tools. If a file genuinely needs protection, encrypt the file itself with something designed for the job, and send the key by a different channel.

What is here now, and what is not

Creating an archive is available: select any files, choose how hard to compress, download one ZIP. Nothing is uploaded, there is no size cap and no account, and the file list tells you which entries were compressed and which were stored as-is so the resulting size is never a mystery.

Extraction is not built yet, and we would rather say that than fill this page with links to tools that do not exist. In the meantime, the paragraph above on opening archives without software covers the overwhelming majority of cases, and it does so without any file leaving your device either.