Online 7z viewer
A .7z is the archive the operating system usually refuses — Windows Explorer and macOS Archive Utility do not understand 7z's LZMA compression, so opening one normally means installing 7-Zip first. An online 7z viewer skips that: you drop the .7z on ZipTool and it is decoded in your browser, so you can browse the file tree and preview files with nothing installed and nothing uploaded. A viewer is browse-first — you see what is inside the 7z without unpacking the whole archive to disk. To start, open the 7z page; for background, see what is a 7z file, and for full opening steps, how to open a 7z file.
ZipTool (ziptool.app) is an online 7z viewer that decodes the archive entirely in the browser using a WebAssembly build of 7-Zip. You open it, drop a .7z onto the page (or paste a direct URL), and the file tree renders locally. Because the parsing happens client-side, the archive never leaves your device — there is no upload, no server, and nothing stored. Confirm it yourself: open a 7z, then disconnect from the internet; browsing, searching, and previewing keep working.
How an online 7z viewer works
A "viewer" differs from an "extractor." An extractor decompresses the whole archive and writes the original files to disk. 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 unless you choose to save it.
In ZipTool the workflow is: add the .7z (drag-and-drop, the file picker, or a URL), the browser reads the bytes locally, and the WebAssembly 7-Zip module walks the archive and builds the file tree on the left. From there you search the tree by name, expand folders, and click any entry to preview it. The whole loop runs in your tab; the network is used only to load the page and (once, then cached) the decoder module. When you do want the files out, see extracting a 7z online.
What you can preview inside the 7z
The point of a viewer is not just to list files — it is to let you actually read them without unpacking. ZipTool previews the common contents inline:
- Code and config — JavaScript, TypeScript, JSON, Python, Markdown, HTML, CSS, YAML, XML, and many more open in a syntax-highlighting editor. You can read a bundled script straight out of the 7z.
- Images — PNG, JPG, GIF, WebP, SVG, and other common formats render inline.
- 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 the 7z opens as its own archive without leaving the page. Anything the viewer cannot render is still listed by name and size.
Why "online" does not have to mean "uploaded"
The phrase "online 7z viewer" raises an obvious question: if it runs in the browser, is my archive being uploaded somewhere? For many "online 7z" tools the honest answer is yes — you upload the file, a server decodes it, and the listing comes back. ZipTool is built the other way: the page loads, the WebAssembly 7-Zip runs locally, and your file contents are not transmitted anywhere.
This matters for privacy and for verifiable trust. Open a 7z, open DevTools, and watch the Network tab: you see the page load and a one-time fetch of the decoder, but no upload of your file. Then unplug your network and confirm the viewer keeps working. For the confidentiality angle (backups, software distributions, sensitive bundles), see the private zip viewer and the broader security and privacy treatment.
Honest limits
A browser-based 7z viewer is capable, but it has real boundaries worth knowing.
- Large 7z archives are heavy. LZMA decoding is more CPU- and memory-intensive than ZIP's Deflate, and a solid archive is one stream. Very large 7z files can be slow or exhaust a browser tab's memory.
- Password-protected 7z needs the password. ZipTool can decrypt AES-encrypted 7z archives when you supply the password; it cannot bypass encryption you do not have the key for.
- It is a viewer. ZipTool browses and previews; it can also extract a 7z to a folder or bundle. But it does not create 7z files — use the desktop 7-Zip program to produce one.
- Client-side parsing is not a security guarantee. A malicious archive is still malicious. Parsing in a sandboxed tab limits the blast radius, but "opens in a browser" is not the same as "safe to open from an untrusted source." See malware in zip files.
Frequently asked questions
Is the online 7z viewer really free?
Yes. Browsing the file tree, searching, and previewing files inside a 7z is completely free, with no account and no install — open the page in a modern browser and drop a 7z in. Core viewing always will be.
Do you upload my 7z?
No. The archive is decoded entirely in your browser using a WebAssembly 7-Zip module; your file contents are never transmitted to a server, never stored, and never handed to a third party. The only network traffic is the page and a one-time fetch of the decoder. Confirm it in DevTools (the Network tab shows no upload) and by disconnecting from the internet after the page loads — browsing and previewing keep working.
Why will Windows or macOS not open my .7z file?
The built-in tools do not understand 7z's LZMA/LZMA2 compression, so they refuse the file. You need a 7-Zip-compatible decoder. ZipTool provides one in the browser (no install), or you can install the desktop 7-Zip program.
Can I search inside the 7z without extracting?
Yes. Once the archive is loaded, the search box filters the file tree by name across the whole 7z — useful for finding one file in a large bundle without unpacking it. The search runs locally against the in-memory tree; nothing about your query leaves the browser.
What is the difference between viewing and extracting a 7z?
Viewing leaves the archive intact and renders files on demand — you look inside without writing anything to disk. Extracting decompresses the entries and writes them out as real files. ZipTool does both: browse and preview first, then extract when you want the files out. See extracting a 7z online.