The situation turns up on Microsoft's own community forums in almost exactly the same words every time. Someone has a folder of .one files — university notes, meeting minutes, a research diary, a business's working records — from a OneNote install that is long gone. The current app won't take them. Nobody has a spare copy of the version that made them. And the notes inside are not the sort of thing you can just write again.

The good news is that a .one file is a real, self-contained file sitting on your disk, and its structure is publicly documented by Microsoft. It is not encrypted by default and it is not a dead end. Here is every route we know of, honestly compared.

First, work out what you actually have

Two files get muddled constantly:

  • .one — a section. This is the file that holds your pages and your typed note text. This is the one that matters.
  • .onetoc2 — a table of contents for a notebook folder. It records which sections exist and in what order. It contains no page text at all, so recovering one gets you nothing but a list.

If you are holding only .onetoc2 files, the notes themselves are somewhere else and finding them is the job — our guide on where OneNote files are stored on disk covers the usual hiding places. If you have .one files, read on.

Before you try anything: copy the files first. Put a copy of every .one somewhere separate and work only on the copy. Some of the routes below convert or upgrade a file in place, and an upgrade is a one-way door — a file converted to a newer format can no longer be read by the older app. Copies cost nothing and remove the risk entirely.

Route 1 — the OneNote desktop app for Windows (free)

This should be your first attempt, because it is free and it is the route with the best chance of giving you a fully working notebook back rather than just the text.

The point most people miss: the desktop OneNote app for Windows is the only version that works with notebooks stored on a local hard drive. The web version and the app that shipped with Windows 10 are built around notebooks kept in OneDrive or SharePoint, which is why handing them a loose .one gets you nowhere. OneNote for Windows is available as a free standalone download from Microsoft and does not require an Office subscription to install.

Once it is installed, the sequence for a loose section file is:

  1. Right-click the .one file in File Explorer and choose Open with › OneNote.
  2. It appears in the app under Opened Sections rather than inside a notebook.
  3. Create a new notebook, then right-click the section tab and choose Move or Copy to put a copy of it into that notebook.

If you instead get a message about the section having been created in an older version, that is a known and documented situation with its own fix — we have written it up separately in what the “older version of OneNote” message means.

Where this route stops: sections saved in the original OneNote 2003 format are not supported by the modern desktop app at all, and getting them forward needs an intermediate version that is now genuinely hard to obtain. It also assumes you have, or can get to, a Windows machine. On a Mac the picture is different again — see opening a local .one file on a Mac.

Route 2 — check for a cloud or backup copy first (free)

Worth ten minutes before you go any further, because it can make the whole problem disappear:

  • If the notebook ever synced, sign in at onenote.com or look in OneDrive › Documents › OneNote Notebooks. A synced copy may still be there even if the local one is broken.
  • OneDrive and SharePoint keep version history per file, so an earlier, healthy version of a section may be one right-click away.
  • The OneNote desktop app keeps its own automatic backups, by default under %LOCALAPPDATA%\Microsoft\OneNote\16.0\Backup. Microsoft documents this folder and it is often full of usable .one files that people never knew existed.
  • Deleted pages and sections sit in the Notebook Recycle Bin, and Microsoft's documentation puts the retention window there at 60 days.

Route 3 — open-source parsers (free, but technical)

Microsoft published the OneNote file-format specifications, and several people have written open-source code against them. If you are comfortable at a command line, these are real options and they cost nothing:

  • onenote2xml — Python modules that read .one sections and .onetoc2 notebooks and emit XML or JSON.
  • pyOneNote — a lightweight reader originally written for security analysis, useful for pulling structure and embedded objects out of a file.
  • one-extract — a script for extracting files and metadata from .one.
  • Aspose.Note FOSS — an open-source library with a Python distribution that walks the document tree and returns text nodes.

Be realistic about what this involves. You will be installing Python, reading a README, and getting raw XML or JSON out at the far end — not a tidy notebook. Coverage varies between projects and between file versions, and none of them promises to handle every section it meets. For one file and a curious afternoon, it is a perfectly good answer. For forty files and a deadline, it is a project.

Route 4 — a local, read-only recovery tool (what we make)

OneNote Rescue exists for the narrow case the routes above leave behind: you have a .one section that nothing will open, you cannot get to a working OneNote, and what you actually want is the typed text back in a form you can read and keep. It is a small desktop app for Windows and Mac, and it opens the file read-only — the source is copied to a temporary location and only the copy is read, so the original's bytes and timestamp are untouched — and writes out your page titles and note text as plain text, a readable per-page HTML notebook, and a JSON report of what it found. The app’s only online action is checking your licence key with Lemon Squeezy; your .one file and everything recovered from it stay on your machine. There is no account to create.

Honest scope, so there are no surprises. OneNote Rescue recovers page titles and note text. From a OneDrive-format section it also writes the embedded images out as real files next to the notebook — along with any other embedded file whose type it recognises by its file signature — each with its SHA-256 recorded in the report. From a classic desktop revision store, embedded files are noted in the report but not extracted in this pass. Ink and handwriting strokes are noted, not converted to text, and any object it cannot identify is listed as present and not extracted rather than guessed into a file. Rich formatting and the exact page hierarchy are simplified into readable text. Nothing is ever decrypted or bypassed: password-protection markers are flagged in the classic revision store, and are not detected in the OneDrive-format container in this pass.

Supported operating systems: Windows 10 and 11 (64-bit), and macOS 10.15 or later. One purchase covers both, so you can recover the files where they already are — no copying them to another machine first.

Put bluntly: if your notebook is mostly typed notes, this reads them back. If it is mostly scanned pages or handwriting, it recovers the text around them, not the drawings. And if a working OneNote will open your file, use OneNote — it will give you more back than we can.

What no route will do

Two limits are worth stating clearly, because plenty of pages on this topic are vague about them.

Password-protected sections. OneNote encrypts these properly. A tool can tell you a section is protected; recovering the contents requires the password. Any product implying otherwise is describing password cracking, which is a different activity with different legal consequences, and not one we take part in.

Notes that were only ever in the Windows 10 app's cache. The app that shipped with Windows 10 kept notes in a local cache rather than as loose .one section files. If that is your situation, .one tooling is not the right instrument — our guide on what to do after the Windows 10 OneNote app retired walks through what applies instead.

The short version

  1. Copy the files. Work on copies only.
  2. Check OneDrive, version history, the Backup folder and the Notebook Recycle Bin.
  3. Install the free OneNote desktop app for Windows and try Open with › OneNote.
  4. If you are technical, try an open-source parser.
  5. If none of that lands and you just need the text, a focused local tool is the remaining option.

We would rather you got your notes back for free at step three than paid us at step five. That is genuinely the better outcome, and it is why the free routes are at the top of this page rather than the bottom.