Deltos

a notepad with tabs

Every tab lives inside one file on disk — the same idea as an Excel workbook holding many sheets, but for plain text. Open the file, every tab is there. No scattered notes.

Download for Windows version 2.0.9 · Windows 10 or later

Deltos with a notebook of tabs open, categories in the sidebar.

Four levels, matching a paper filing cabinet

Archive: A folder holding several .dlt files.
Notebook: One .dlt file, like one wallet in the cabinet.
Category: A coloured divider inside the notebook.
Tab: A page behind that divider.

Tick a category to show its documents; tick several to see them together. Drag a tab onto a category to file it. Each category picks its own colour.

The file is yours

A notebook is a .dlt file: readable UTF-8 JSON, so it diffs and greps fine and you can recover the text with any editor if you ever want out.

{
  "format": "Deltos",
  "version": 1,
  "active": 0,
  "tabs": [
    { "name": "Shopping", "content": "oat milk\nbread\n" }
  ]
}

An archive (.dlx) is just a ZIP. Rename it to .zip and your notebooks are right there — the same promise the readable JSON makes.

The name

A delta-os was the Greek writing tablet: hinged leaves that folded together, several writing surfaces bound into a single object. That is what a .dlt file is.