Online zip file viewer

How an online zip file viewer works

A "viewer" is different from an "extractor", and the distinction is worth stating. An extractor decompresses the archive and writes the original files to a folder on your computer, where other applications can open them. A viewer leaves the archive intact and renders its contents on demand — you browse the tree, click a file, and the viewer shows you that one file. Nothing is unpacked onto your disk unless you choose to save it.

In ZipTool, the workflow is: add an archive (drag-and-drop, the file picker, or a URL), and the browser reads the bytes locally. zip.js running in the page walks the central directory and builds the file tree you see on the left. From there you can search the tree by name, expand folders, and click any entry to preview it. The whole parse-and-render loop runs in your tab; the network is only used to load the page (and, if you used a URL, to fetch the archive once). For the browse-only workflow in detail, see viewing the contents of a zip without extracting.

What you can preview inside the zip

The point of a viewer is not just to list files — it is to let you actually read them without unpacking the archive. ZipTool previews the most common contents inline:

• Code and config — JavaScript, TypeScript, JSON, Python, Markdown, HTML, CSS, YAML, XML, and many more open in a syntax-highlighting editor (Monaco). You can read a bundled script or a config file straight out of the archive.
• Images — PNG, JPG, GIF, WebP, SVG, and other common formats render inline, so you can inspect an archive of screenshots or assets.
• Documents — PDFs render in the page, and plain-text files show as readable text.
• Audio and video — common audio and video formats play inline without a separate player.
• Nested archives — a zip stored inside another zip (or a .jar / .whl / .apk, which are ZIP under the hood) can be opened as its own archive without leaving the page. Anything the viewer cannot render is still listed by name and size.

Formats an online zip viewer opens

Because so many file types are secretly ZIP containers, one viewer covers a wide range. ZipTool opens plain .zip plus the ZIP family — .apk, .epub, .jar, .whl, .xpi, .war, and Office OOXML files like .docx and .xlsx — and decodes non-ZIP formats directly: .7z (via a WebAssembly 7-Zip), .rar (via a WebAssembly unrar), .tar.gz, .tar, and .gz. Each of these can be browsed and previewed the same way. Encrypted RAR entries and split / multi-volume RARs are not supported in the browser.

This is also why a single in-browser viewer can stand in for a drawer full of per-format tools: there is no separate reader required for each extension. For the bigger picture on which formats are ZIP under the hood, see the archive file formats reference.

Why "online" does not have to mean "uploaded"

The phrase "online zip viewer" raises an obvious question: if it runs in the browser, is my archive being uploaded somewhere? For most "online unzip" sites the honest answer is yes — you upload the file, a server extracts it, and the listing comes back. ZipTool is built the other way: the page loads, then does all of its work locally. Your file contents are not transmitted to a server, are not stored, and are not handed to a third party.

This matters for two reasons. The first is privacy: when the file never leaves your device, there is no server-side copy to leak, retain, or scan. The second is trust you can verify yourself — open an archive, open DevTools, and watch the Network tab; you will see the page load and (if you used a URL) a single fetch, but no upload of the file. Then unplug your network and confirm the viewer keeps working. For the confidentiality angle (NDA work, client deliverables, regulated files), see the private zip file viewer page, and for the broader treatment see security and privacy.

Honest limits

A browser-based viewer is genuinely useful, but it has real limits worth knowing before you rely on it.

Things to keep in mind:

• Large archives and zip bombs. A "zip bomb" is an archive that decompresses to a size many times larger than the file on disk (ratios of a million-to-one and beyond are possible). A browser tab has finite memory; an archive designed to exhaust it can freeze or crash the page. Open archives from sources you trust, and be cautious with tiny files that claim to contain enormous uncompressed data.
• It is a viewer, not an extractor. ZipTool browses and previews; it does not unpack a whole archive to disk, decrypt password-protected entries, or repair damaged archives. When you need the real files written out, use a desktop extractor.
• Encrypted and some exotic formats. Password-protected (encrypted) RAR entries and split / multi-volume RARs are not supported in the browser, and there is not yet a client-side decoder wired in for .7z. These are honest gaps, not limitations hidden behind marketing copy.
• Client-side parsing is not a security guarantee. A malicious archive is still malicious. Parsing runs in a sandboxed browser tab, which limits the blast radius, but "opens in a browser" is not the same as "safe to open from an untrusted source."

Frequently asked questions