Guide
Private in-browser file viewing (what stays local)
How Filelathe handles files in your tab, what may hit the API, and why that matters versus upload-to-convert sites.
Local-first viewing
Dropping a file into Filelathe reads it with the browser File API. Media playback, PDF embedding, and image editing use object URLs and WASM/worklets in your tab.
That is different from sites that require uploading the whole file to a server before you see a preview.
Office files
Word, Excel, and PowerPoint are parsed in the tab too. A .docx is read from its ZIP package (word/document.xml), a .doc from the WordDocument stream, a .xlsx or .xls from the first sheet, and a .pptx on a local slide canvas. A classic .ppt is an OLE listing with peeked text, not a slideshow. An .odt is the prose from content.xml.
Each of those pages states what the viewer will and will not show. None of them is an upload-to-convert step.
When the network is used
Composing a UI may send metadata (name, type, small samples) so the right tool or an invented mini-app can be chosen. Rate limits apply on those API routes.
If you are handling secrets (.env, private keys), prefer local files you trust.