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.OTM file extension

To open .OTM files on Windows, install or use LibreOffice (Writer), then open Writer and use File → Open to select the .OTM file.

To open an .OTM file, use an OpenDocument-compatible office suite—most commonly LibreOffice Writer. Don’t rename the file extension; instead open it from within the office app (or use “Open with” on desktop).

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Last updated: June 10, 2026

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .OTM files

Use these platform-specific instructions to open .OTM files safely.

Windows

  1. Install or use LibreOffice (Writer), then open Writer and use File → Open to select the .OTM file.
  2. If double-clicking doesn’t work, right-click the file → Open with → choose LibreOffice Writer and (optionally) set it as the default for .otm.
Full Windows guide

Mac

  1. Open LibreOffice Writer, then use File → Open and select the .OTM file.
  2. If Finder doesn’t know what to use, Control-click the file → Open With → LibreOffice and confirm.
Full Mac guide

Linux

  1. Open LibreOffice Writer and use File → Open to open the .OTM file.
  2. If opening from the file manager, use Open With → LibreOffice Writer (desktop environments may detect it by the shared MIME type mapping).
Full Linux guide

iOS

  1. There is no widely established native iOS support for .OTM; if it won’t preview, transfer the file to a desktop with LibreOffice to open and edit it.
Full iOS guide

Android

  1. There is no widely established native Android support for .OTM; if it won’t open, move it to a desktop with LibreOffice to open and work with it.
Full Android guide

Security notes

  • .OTM is an office document template format; treat unexpected .OTM files like other office documents—only open templates from senders you trust, especially in business email contexts.
  • If an .OTM file is prompting you to enable unusual content or workflows, stop and verify the source; templates can influence how new documents are created and may embed content that you didn’t expect.
  • Be cautious with files that have been renamed to .otm; verify the MIME/type detection in your OS or open it from LibreOffice to confirm it is actually an OpenDocument master template.

Can't open this file?

These are the most common causes and fixes when .OTM files fail to open.

Common reasons

  • The file opens as “unknown format” or won’t open
  • I expected a normal document, but it behaves like a template/master workflow
  • File association or MIME type mismatch on Linux

Fix steps

  1. Open the file in LibreOffice Writer (File → Open) instead of relying on double-click.
  2. If you must use “Open with,” explicitly choose LibreOffice Writer and set it as the default for .otm.

Recover a deleted or lost .OTM file

If the file was deleted by mistake or the drive was formatted, data recovery software may be able to get it back. Stop writing to that drive right away, because new data can overwrite what you want to recover.

MiniTool Power Data Recovery

Windows software that recovers deleted or lost files from PCs and external drives such as HDDs, SSDs, USB drives and memory cards, after deletion, formatting or a crash.

Wondershare Recoverit

Windows and Mac software that recovers deleted or lost files from computers and external drives such as HDDs, SSDs, USB drives and SD cards.

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OS-specific troubleshooting

What is a .OTM file?

.OTM is the file extension for an OpenDocument Text Master Template, with the registered media type application/vnd.oasis.opendocument.text-master-template. It is part of the OASIS OpenDocument Format (ODF) family used for office documents and templates. In LibreOffice, it relates to “master documents” workflows (where a master document can manage multiple subdocuments) and their templates.

Background

The .OTM format belongs to the OpenDocument Format (ODF) standard maintained by OASIS. ODF defines a family of interoperable office document and template types, and .OTM specifically targets master-document template use cases.

Common MIME types: application/vnd.oasis.opendocument.text-master-template

Further reading

Authoritative resources for more details on the .OTM format.

Common .OTM issues

The file opens as “unknown format” or won’t open

This usually happens when no ODF-capable office suite is installed/associated, or when the file is being opened in an app that doesn’t support ODF master templates.

  1. Open the file in LibreOffice Writer (File → Open) instead of relying on double-click.
  2. If you must use “Open with,” explicitly choose LibreOffice Writer and set it as the default for .otm.

I expected a normal document, but it behaves like a template/master workflow

.OTM is a master document template type; it may be intended for creating new master-document-based projects rather than being a standalone “final document.”

  1. In LibreOffice Writer, review the master document/template workflow and how the file is meant to be used in your organization.
  2. If you were sent the wrong file, ask the sender for the actual master document or final exported document format they intended to share.

File association or MIME type mismatch on Linux

Desktop environments commonly use the shared-mime-info database to map *.otm to the ODF master template MIME type; if your system MIME database is outdated, the file may not be recognized correctly.

  1. Try opening the .OTM directly from LibreOffice Writer even if the file manager doesn’t recognize it.
  2. Update your system’s MIME database/packages (shared-mime-info) so *.otm is correctly mapped to application/vnd.oasis.opendocument.text-master-template.

FAQ

What does .OTM stand for in this context?

Here it refers to an OpenDocument Text Master Template (master document template) in the ODF family.

What is the MIME type for .OTM?

The registered media type is application/vnd.oasis.opendocument.text-master-template.

Can I convert an .OTM by renaming it to .ODT or another extension?

No. Renaming only changes the extension label. Use the office suite’s Save As/Export features if you need a different format.

Is .OTM the same as a master document (.ODM)?

No. LibreOffice documentation distinguishes master documents (.odm) from master document templates (.otm); .otm is for templates used to create master-document-based projects.

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