Improve ODF support

[juliusknorr]

New files default to OOXML formats (.docx, .xlsx, .pptx), ODF editing has known fidelity gaps, and there is no admin-level option to enforce ODF as the default. This initiative tracks the work to make ODF a fully supported, first-class format in Euro-Office.

Current state

ODF is the ISO-standardised open document format championed by LibreOffice and mandated by public administrations across the EU. Euro-Office is positioned as an open, sovereign alternative to proprietary office suites, making robust ODF support a strategic requirement, not just a feature request.

The current state inherited from upstream has several known shortcomings:

• Default format is OOXML. New files are created as .docx/.xlsx/.pptx with no admin or user setting to change this default to ODF. This has been a long-standing community request upstream.
• ODF files open read-only in some configurations. Despite enabling ODF editing in settings, .odt, .ods, and .odp files can open in read-only mode.
• Fidelity gaps when round-tripping ODF. Formatting, styles, and certain features are lost or altered when opening and re-saving ODF documents, making reliable ODF workflows impractical.
• No ODF default on mobile. The mobile editors do not support saving in ODF — all saves are forced to OOXML regardless of the source file format.
• ODF template formats (.ott, .ots, .otp) are poorly handled. Template types are not correctly associated and may not open in the editor at all without manual workarounds.

Next steps

• Add admin setting for ODF as default new file format (Euro-Office/nextcloud-onlyoffice)
• Fix ODF files opening in read-only mode when ODF editing is enabled (Euro-Office/nextcloud-onlyoffice)
• Research and identify gaps in ODF support for different file formats
  • [Core] Audit and improve ODF round-trip fidelity for Writer (.odt) — Euro-Office/sdkjs / Euro-Office/core
  • [Core] Audit and improve ODF round-trip fidelity for Calc (.ods) — Euro-Office/sdkjs / Euro-Office/core
  • [Core] Audit and improve ODF round-trip fidelity for Impress (.odp) — Euro-Office/sdkjs / Euro-Office/core
  • [QA] Create an ODF fidelity test document corpus and automated regression checks (Extend document conversion test coverage core#92)
    Work packages can be tracked as subtasks

References

• Upstream community thread: Make ODF a first-level citizen in ONLYOFFICE
• Upstream PR (experimental ODF default): onlyoffice-nextcloud#886
• Upstream issue (configure ODF creation): onlyoffice-nextcloud#224
• Upstream issue (ODF opens read-only): onlyoffice-nextcloud#811
• Further analysis by @pplupo in ODF Gap analysis + potential bugs - Done with Claude Opus 4.8. DesktopEditors#63

Data loss / corruption (highest priority)

• ONLYOFFICE/DocumentServer#3139 — Formatting is incorrect when reloading a DOCX file saved as an ODT file (confirmed bug, regression 7.x → 8.x)
• ONLYOFFICE/DocumentServer#1886 — OnlyOffice generates corrupted .ods file containing URLs due to invalid content.xml
• ONLYOFFICE/DocumentServer#2102 — Date value lost/erased after reading an .ods file created by LibreOffice and saving again to .ods
• ONLYOFFICE/DesktopEditors#836 — OnlyOffice rewrites .ods to custom format, makes it unreadable for other editors

Spreadsheet (.ods) fidelity

• ONLYOFFICE/DocumentServer#1321 — LibreOffice/Excel ODS file has formula not calculated after open
• ONLYOFFICE/DesktopEditors#1044 — Saving a file in .ods format creates incompatibilities with LibreOffice ("maximum number of columns per sheet was exceeded")
• ONLYOFFICE/DocumentServer#3430 — Attached .ods file does not open (chart causes hang)

Text document (.odt) fidelity

• ONLYOFFICE/DocumentServer#3056 — Footnote numbering in Document Server for ODT files (footnote 1 → 11 → 111 on each reload)
• ONLYOFFICE/DocumentServer#2735 — Alternative text for images lost when importing from .odt
• ONLYOFFICE/DocumentServer#2130 — .odt incompatibility with LibreOffice Writer (tab spacing differs)
• ONLYOFFICE/DocumentServer#1375 — Change context of ODT file after resave it as ODT (tracked changes corruption)

Presentation (.odp) fidelity

• ONLYOFFICE/DocumentServer#3220 — Subscript & superscript text is too small when opening LibreOffice .odp document
• ONLYOFFICE/DocumentServer#2634 — Hyperlink to the slide / place in the document do not work properly for .odt / .odp / .ods format files

Integration layer (Nextcloud app)

• ONLYOFFICE/onlyoffice-nextcloud#811 — ODF and MS DOC/XLS/DOT/DOTX files are opened only in read-only mode
• ONLYOFFICE/onlyoffice-nextcloud#1117 — File format settings not saved after modifications (.odt checkbox doesn't persist)
• ONLYOFFICE/onlyoffice-nextcloud#462 — Incompatible files not saved after edit (ODT/CSV edits silently dropped)
• ONLYOFFICE/onlyoffice-nextcloud#475 — UX: Help user with .odt files (conversion messaging)

Collaboration

• ONLYOFFICE/DocumentServer#2637 — Track changes option "ON for me and everyone" does not propagate to other users in .odt / .rtf (closed as not planned upstream)

[Thatoo]

Can't wait for an Euro-Office working with ODF format by default as well as it does now with ooxml format.
Haven't been that excited by a github open issue for quiet a while.
Big up to Euro-Office team to have it on their roadmap!