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/Organizing files

Organizing files

Viewing & previewing files

Open a file to read or watch it right in the browser, no download, no plaintext leaving your device.

Thumbnails & type icons

Before you even open a file, the grid shows you what it is. Images and videos get a real thumbnail (a small preview of the file itself) and everything else gets a crisp, macOS-style type icon: a colored glyph and label (Document, Image, Video, Audio, Spreadsheet, Code, Archive, and so on) on a little page tile.

  • •Generated on your device. A thumbnail is built by decrypting the file in your browser, drawing it to a canvas, and encoding a tiny preview, the same zero-knowledge path as the viewer. For a video, zcrypt grabs a frame a little way in so you get a representative still rather than a black opening frame.
  • •Lazy and cached. Each preview is generated the first time its card comes into view, then cached locally on your device, so it appears instantly next time without decrypting the file again.
  • •Icons for the rest. Files that aren’t images or video, and very large files that aren’t worth decrypting just for a preview, fall back to their type icon instead.

Previews never leave your device

Thumbnails are made from the decrypted file in your browser and kept only in your browser’s local cache. They are never uploaded, your storage platform and our servers only ever hold the encrypted chunks.

The full-screen viewer

Click a file to open the full-screen viewer, an overlay that renders the file in place. It is the quickest way to check a document, scrub a video, or skim a folder of images without saving anything to disk.

What it can preview

The viewer handles a wide range of formats directly in the browser:

  • •Images, video, and audio with native playback controls.
  • •PDF documents, page by page.
  • •DOCX word-processing documents.
  • •HTML: rendered sanitized, with scripts disabled.
  • •Markdown, rendered to formatted text.
  • •CSV and TSV as tables.
  • •Text and code files.

HTML is rendered safely

HTML previews are sanitized and have scripting disabled before they are shown, so opening an HTML file can't run code or phone home from inside your vault.

Decrypted on the fly

Previewing is zero-knowledge. zcrypt fetches the encrypted chunks, then decrypts and decompresses them in your browser just long enough to render the preview. The plaintext stays local. It is never written to your storage platform and never sent to our servers.