How to open a file in your browser
Drop the file on the viewer above, choose it or paste it. It opens the way it should, a picture to zoom, a PDF to scroll, a spreadsheet as a table, JSON as a tree, without installing anything. Your browser does the work, so the file stays on your device.
Drop the file
Its type comes from its contents, not its name, so a file with no extension or the wrong one still opens as what it is.
Look at it
View shows it. Text and Source show the words of text formats, Bytes shows every byte in hexadecimal, and Details lists its size, dates, pixels, pages or length.
Take it further
Open in sends the file to another webdave tool in a new tab: the image editor, the converter, the Large CSV viewer and more. It is handed over inside your browser, not uploaded.
What it opens
Each format has a page of its own with what the viewer shows for it.
Pictures
Archives
Anything else
Anything else opens as bytes. HEIC photos, TIFF, PowerPoint, RAR, 7-Zip and old Office files are recognised and named, and will open properly later.
Files with no extension
Most formats start with a signature: a PNG with the bytes 89 50 4E 47, a PDF with %PDF, a ZIP (and so every Word and Excel file) with PK. The viewer reads those first bytes, looks inside ZIPs for Word and Excel parts, and reads text formats from their first lines. So img opens as the PNG it is, and Details tells you to name it img.png. When the tools under Open in get the file, they get it with the right extension.
Where the file goes
Nowhere. The viewer is a page that runs in your browser: it reads the file from your disk and draws it there. Web pages and documents are shown without running their scripts, and pictures they link to on the web are not fetched, so opening a file never tells anyone you did.
Questions
Drop it on the viewer. It reads the file's first bytes, where most formats keep a signature, and opens it as what it is. Details then names the right extension.
No. It is read by your browser on your device and nothing is sent anywhere. You can check in the browser's network tools.
Every file opens as bytes in a hex view, however large it is. Formats it recognises but cannot show yet, such as HEIC, RAR or old Office files, are named.
Pictures, video and audio as large as your browser can play. CSV and Excel sheets go to the Large CSV viewer, which handles millions of rows. Text, JSON, YAML and XML up to 64 MB, and bytes of any size.