Trilium allows importing from OneNote. Currently the only mechanism supported is via the Microsoft Graph API which requires you to authenticate in a browser in order for the notes to be obtained by Trilium.

Import process

1. In the Note Tree, right click and select Import into note.
2. In the Import from section, select OneNote.
3. Press the Connect button:
   1. On the desktop app, you will be redirected to Microsoft's authentication screen where you can log into your account.
   2. On the web app, the process is slightly more involved as it requires copying the code to clipboard, accessing the link, pasting the code and then signing in once more.
4. After the connection is successful, you should be able to see a list of sections that can be imported. Simply check the ones to import and press the Import selected button.
5. Wait for the import to finish.

Supported features

The following features are preserved by Trilium during the import process:

• Basic formatting (bold, italic, underline, strikethrough, subscript, super script, inline code, font sizes, headings, colors, highlights).
  • Black-colored text is intentionally stripped to allow it to work in dark themes.
• Lists with different bullet types.
• Tables
  • Cell backgrounds are preserved, including a best-effort hue correction because the colors returned by the Graph API are sometimes incorrect.
  • Cell widths are also preserved proportionally, with the only difference that tables in Trilium have a percentage-based width, not fixed pixel sizes.
• Images and Attachments.
  • Screen clippings are also properly supported since v0.104.1, displaying their timestamp as a figure caption.
• To-do lists
• Hand-drawing is preserved and displayed as an SVG image inside the note
  • OneNote's default color (black) is special since it also renders as white for dark themes. Since v0.104.1, this is also supported by using a special SVG tweak which reacts to light/dark themes.
• Links between other imported pages are converted to Internal (reference) links if the text of the link matches the name of the page, or plain links otherwise. If the pages are not part of the import, the original onenote: link is kept.
• Tags (apart from to-do lists) are mildly preserved by converting them to emojis. This loses their searchability. Since Trilium has no concept of inline attributes or badges, this is considered a middle-ground.

Regarding the note structure:

• The order of the pages within a section is maintained.
• Sub-pages and section groups are maintained by nesting notes in a hierarchical structure.
• Creation and modification of both notes and sections is preserved. The order of section or section groups is not preserved (see limitations).

Error management and reporting

The OneNote importer uses Microsoft's Graph API which handles the HTML export (that we later post-process for Trilium use). The Graph API itself has to process the OneNote pages before sending them to us, and as such it's a time-consuming operation that is directly proportional to the number of notes and the complexity/size of the notes.

The Graph API throttles access if it detects too many operations. The importer takes that into account, but sometimes this means that most of the time is spent waiting for the Graph API to unblock access rather than actually importing data.

In addition, some pages may fail at the Graph API level due to an internal timeout on their side or other issues. Trilium will try to refetch pages in order to avoid that but sometimes pages cannot be retrieved even after multiple retries. In that case, the importer will still create a corresponding note in Trilium but with an error report instead of a content. This preserves  Internal (reference) links and makes it easy to identify and manually fix the pages that failed.

At the end of the import, the top-level note called OneNote import will contain information about how the import went:

• The number of notes imported;
• The success rate;
• A list of notes that could not be imported, as well as the failure reason;
• Pages whose images/attachments failed to download
• How long the import spent waiting out throttling.

To avoid cases in which the import is fundamentally broken (e.g. an expired sign-in), the import will error out if it fails to import 6 pages in a row.

Attributes

Pages imported from OneNote have a few built-in labels:

• oneNotePageId, with the corresponding page ID in OneNote. This can be used to identify the original OneNote page. Trilium doesn't use it in any way at this moment.
• oneNoteImportFailed attached to notes that couldn't be imported. This can be used to quickly Search for failed notes.

Limitations

Regarding OneNote's freehand structure

OneNote is fundamentally different to Trilium in structure because it allows freehand drawing to coexist with text, and text boxes can be placed anywhere in the document (e.g. a common use case is to have columns). Trilium has a document flow mechanism for Text notes which means that it can't be freely positioned.

To cope with this difference, Trilium will flatten the text structure into normal paragraphs. The paragraphs will be ordered visually based on the original position of the text boxes, but their horizontal position will not be preserved. Parallel text such as columns may appear interleaved which can cause problems.

In addition, drawing in OneNote can be interleaved with text boxes. Text notes in Trilium do not allow for this feature, so all drawing will appear at the end. For some use cases (diagrams, for example) this will work fine, but if you have highlights or other text-dependent drawings they will appear out of order.

Password-protected sections

OneNote supports encryption at section level; when importing a notebook that contains these password-protection sections, Trilium will not be able to read the content of password-protected sections so they will appear empty. This is not a limitation of Trilium, the information is simply not available from the source (Graph API).

The section itself is kept for reference and all the sections that could not be imported will be shown in the report (the top-level note called OneNote import).

To unprotect a section in OneNote Desktop, right click on the protected section → Password Protect This Section and press Remove Password and sync. Then reimport either only the protected sessions or the remove everything and start the import from scratch.

Other limitations

The following are known limitations due to how the information comes from the import (Microsoft Graph API), which means that they cannot be fixed.

• The order of the sections (and section groups) is not available, the sections are ordered by creation date instead.
• Revision history.
• Paragraph indentation.
• Section colors.
• Drawings inside titles, the title might appear incomplete or “Untitled”.

Reporting issues

When importing notes, you might find that some text is not rendered properly or the structure is not properly maintained. As long as this issue is not a fundamental issue (like the issue with freehand text not being preserved exactly), it's a good idea to report it.

When reporting, make sure that you provide the following information:

• Import again the section, checking the debug checkbox before importing. This preserves the original document (and the hand-drawing data if any) as it came through from OneNote's cloud API so that it can be used for comparison.
• Export only the affected page as ZIP, making sure not to accidentally expose any sensitive information.
• Take screenshots of how the note looked like in OneNote and how it ends up in Trilium.
• Attach the ZIP and the screenshots to the issue report.