OTS File (.ots): What It Is, How It Works + Sample Files

The basics

What is an OTS file?

An OTS file is a template for LibreOffice Calc and other OpenDocument spreadsheet apps. Invoices, budgets, timesheets, expense claims and order forms are typical OTS templates. Open one and LibreOffice doesn't open the file itself: it creates a new spreadsheet called Untitled 1 with a copy of the template's sheets, formulas, styles and print settings, and the template stays unchanged for next time.

Inside, an OTS is built exactly like an ODS: XML files in a ZIP package, defined by the OpenDocument standard (OASIS, ISO/IEC 26300). It is the spreadsheet member of the ODF template family, next to OTT for text and OTP for presentations. Microsoft Excel's equivalent is the XLTX.

It holds structure, not just data. Labels, formulas, number formats, cell styles, validation rules and print ranges are the useful part; the input cells are often empty.
The type is inside the file. LibreOffice decides whether a file is a template from the mimetype entry, not from the .ots extension.
Formulas come along. A new spreadsheet made from the template calculates as soon as you type into it.

Anatomy

What's inside an OTS file

Rename an .ots to .zip and it opens like any archive. Our sample-minimal.ots holds only the three entries LibreOffice needs, written by hand: a sheet with a label, an empty input cell and a formula that uses it.

sample-minimal.ots (file list and XML)

$ unzip -l sample-minimal.ots
  Length      Date    Time    Name
---------  ---------- -----   ----
       55  2026-10-27 12:00   mimetype
     1268  2026-10-27 12:00   content.xml
      421  2026-10-27 12:00   META-INF/manifest.xml

Bytes 0-92: 50 4B 03 04 … "mimetype"
            "application/vnd.oasis.opendocument.spreadsheet-template"

content.xml:
<office:document-content xmlns:office="…" xmlns:table="…" office:version="1.3">
  <office:body>
    <office:spreadsheet>
      <table:table table:name="Sheet1">
        <table:table-column table:number-columns-repeated="2"/>
        <table:table-row>
          <table:table-cell office:value-type="string"><text:p>Price</text:p></table:table-cell>
          <table:table-cell/>
        </table:table-row>
        <table:table-row>
          <table:table-cell office:value-type="string"><text:p>VAT 21%</text:p></table:table-cell>
          <table:table-cell table:formula="of:=ROUND([.B1]*0.21;2)"
              office:value-type="float" office:value="0"><text:p>0</text:p></table:table-cell>
        </table:table-row>
        …
      </table:table>
    </office:spreadsheet>
  </office:body>
</office:document-content>

META-INF/manifest.xml (root entry):
<manifest:file-entry manifest:full-path="/" manifest:version="1.3"
    manifest:media-type="application/vnd.oasis.opendocument.spreadsheet-template"/>

150 4B 03 04
The ZIP signature
Every OTS is a ZIP file, like every ODS and XLSX, so the first four bytes don't tell you it's a spreadsheet, let alone a template.
2mimetype
The mimetype entry
First in the package, stored uncompressed and without an extra field, so its name always sits at byte 30 and its content at byte 38.
3application/vnd.oasis.opendocument.spreadsheet-template
The template's type
55 characters, no line break. An ODS has the 46-character application/vnd.oasis.opendocument.spreadsheet here; the extra -template is what makes the file a template.
4<office:spreadsheet>
A spreadsheet
The body holds spreadsheet content, as in an ODS. There are no template-only elements: the template's sheets are ordinary table:table elements.
5<table:table-cell/>
An empty input cell
Where the user types the price. A template usually leaves its input cells empty, or fills them with example values to type over.
6table:formula="of:=ROUND([.B1]*0.21;2)"
A formula
Written in OpenFormula with an of: prefix, cell references in square brackets and semicolons between arguments. It refers to the empty cell, so it shows 0 until a price is typed in.
7office:value="0"
The stored result
Each formula cell also stores its last result, so a viewer that can't calculate still shows something. LibreOffice recalculates when a new spreadsheet is made from the template.
8manifest:full-path="/"
The manifest's root entry
Repeats the package's type. In a valid file it matches the mimetype entry: …spreadsheet-template here.

Under the hood

What makes an OTS different from an ODS

We saved our invoice from LibreOffice Calc twice, as sample-invoice.ots and sample-invoice.ods, and compared the two packages entry by entry. Everything except two entries was byte for byte identical:

Entry	In the OTS	In the ODS
`mimetype`	`…opendocument.spreadsheet-template` (55 bytes)	`…opendocument.spreadsheet` (46 bytes)
`META-INF/manifest.xml`, root entry	`…spreadsheet-template`	`…spreadsheet`
`content.xml`, `styles.xml`, `meta.xml`, `settings.xml`, thumbnail	Identical	Identical

Because the type is inside the package, the extension doesn't decide. In our tests with LibreOffice 24.2, the OTS renamed to .ods still opened as Untitled 1, a new spreadsheet, while the ODS renamed to .ots opened as an ordinary file under its own name. To turn one into the other, save it again in the other format.

Template features

What a good spreadsheet template holds

Our sample-invoice.ots uses the features that make spreadsheet templates hard to break. Each one is stored in the XML, so other apps can read it, and converters can lose it:

Feature	What it does	Where it is stored
Input cells	Yellow cells for the things that change: client, date, lines. They use a cell style called Input.	`styles.xml`: the Input style, with `style:cell-protect="none"`
Protected formulas	Every other cell is locked and the sheet is protected without a password, so a user can't type over a formula by accident.	`content.xml`: `table:protected="true"` on the sheet
Formulas that tolerate blanks	`=IF(OR(B10="";C10="");"";B10*C10)` leaves empty lines empty instead of showing 0.	`table:formula` on each cell
Validation	Quantity and price must be numbers of 0 or more; anything else is refused with a message.	`table:content-validation` in `content.xml`
Number formats	Euro amounts and a long date format, so typed values look right at once.	Data styles in `styles.xml` and `content.xml`
Print range and page style	A4 portrait, with a footer, printing only `A1:D26`.	`table:print-ranges` and the page style

Protection is not security

Sheet protection without a password stops accidents, not people: anyone can switch it off with Tools, Protect Sheet. Even with a password, the data is readable by unzipping the file. Use it to guide users, never to hide anything.

In LibreOffice

Making and using spreadsheet templates in LibreOffice Calc

Make a template: set up the sheets, then File, Templates, Save as Template, give it a name and pick a category. Or use File, Save As with the type ODF Spreadsheet Template (.ots) and save it anywhere.
Use a template: File, New, Templates opens the template dialog; double-click a template. Double-clicking an .ots in your file manager does the same.
Edit a template: in the template dialog, right-click it and choose Edit. Opening the .ots the normal way only gives you a new spreadsheet.
Change the default: right-click a template and choose Set as Default. Every new Calc spreadsheet then starts from it, the job Book.xltx does in Excel's start-up folder.
Leave input cells empty or obviously fake. Our invoice has two example lines to type over; the budget template has no values at all, so its totals start at €0.00.

Comparison

OTS vs XLTX, XLT and ODS

	OTS	XLTX	XLTM	XLT	ODS
What it is	ODF spreadsheet template	Excel template	Excel template with macros	Excel 97-2003 template	ODF spreadsheet
Native app	LibreOffice Calc	Microsoft Excel	Microsoft Excel	Excel 97-2003	LibreOffice Calc
Structure	ZIP of XML	ZIP of XML	ZIP of XML	OLE2 binary	ZIP of XML
What marks a template	`mimetype` entry	Main part content type	Main part content type	A flag in the workbook	(not a template)
Formula syntax in the file	OpenFormula, `of:=SUM([.A1:.A3])`	Excel's, `SUM(A1:A3)`	Excel's	Binary tokens	OpenFormula
Macros	Yes, same extension	No	Yes	Yes, same extension	Yes, same extension

Use OTS when the people filling in the template use LibreOffice, and XLTX when they use Excel. Formulas are translated on conversion, so test a converted template in the app that will use it: we converted sample-invoice.ots to XLTX with LibreOffice and the formulas and the sheet protection came through.

How to

How to open and convert an OTS file

LibreOffice Calc (free; Windows, macOS, Linux) opens OTS files natively, as do Apache OpenOffice and other ODF spreadsheet apps. Collabora Office does the same on phones and tablets.
To a spreadsheet: open the template (which creates Untitled 1) and save it as ODS or XLSX, or run soffice --headless --convert-to ods budget.ots.
To an Excel template: File, Save As, Excel 2007-365 Template (.xltx), or soffice --headless --convert-to 'xltx:Calc MS Excel 2007 XML Template' invoice.ots.
From a spreadsheet or Excel template: soffice --headless --convert-to 'ots:calc8_template' invoice.ods (an XLSX or XLTX works as input too).
Excel and Google Sheets work with ODS spreadsheets. For a template, the dependable route is to create a spreadsheet from it in LibreOffice and send that, or convert the template to XLTX.
In a browser: browsers can't display OTS files, so a link to one downloads it.

Troubleshooting

Common OTS problems and how to fix them

Opening the template gives Untitled 1. That's how templates work. To change the template itself, use Edit in the template dialog.
"The cell or chart you are trying to change is protected." The template locks its formula cells. Type in the input cells, or switch protection off with Tools, Protect Sheet if you made the template.
Totals show 0 or Err:502. An input is empty or text instead of a number. Formulas that test for blanks, as in our invoice, avoid the zeros; validation stops text being typed into number cells.
My template isn't in the template dialog. It's not in a templates folder. Use Import in the template dialog, or Save as Template.
"The file is corrupt" after editing the ZIP by hand. The mimetype entry must be first and uncompressed. With Info-ZIP: zip -X0 new.ots mimetype then zip -Xr new.ots . -x mimetype.
It downloads as a ZIP or opens as the wrong type. The server sends application/zip. Serve .ots as application/vnd.oasis.opendocument.spreadsheet-template.

Security

Is an OTS file safe to open?

Like ODS, an OTS has no separate macro-free extension: any .ots can contain LibreOffice Basic or other scripts, and spreadsheets made from it carry them on. LibreOffice's default macro security only runs macros that are signed by a trusted source or stored in a trusted location. Don't lower it because a template asks you to.

External links. Formulas can pull data from other files or web addresses (WEBSERVICE, links to external sheets). LibreOffice asks before updating external links; say no for templates you didn't make.
Hidden sheets and cells. A template can carry hidden sheets, hidden rows and comments into every file made from it. Check them before sending a filled-in copy outside your organisation.
Formula injection. Data pasted from a CSV into a template can start with = and become a formula. Treat imported text as text.

Free downloads

Sample OTS files to download

Free sample OpenDocument spreadsheet templates for testing uploads, file-type detection, converters and template handling. The invoice and the budget were built in LibreOffice Calc 24.2; the minimal file was written by hand. All were checked with unzip -t, odfpy and a LibreOffice export to PDF. None contains macros, and all names are fictional.

sample-invoice.ots · 27.9 KBDownload

Browsers can't show this kind of file in a page. Download it to open it in the app it belongs to.

What's inside sample-invoice.ots

Browsers can't preview OTS files, so download it and open it in LibreOffice Calc: you get Untitled 1, a new invoice based on it. These are the parts to look for.

Yellow input cells
Client, invoice number, date, payment terms, ten invoice lines and the VAT rate. They use the Input and Money Input cell styles, which leave them unlocked.
Locked formulas
The sheet is protected without a password, so only the yellow cells take typing. Tools, Protect Sheet switches it off.
Line amounts
=IF(OR(B10="";C10="");"";B10*C10) on each line: empty lines stay empty. Two example lines give a subtotal of €402.00.
VAT and total
=ROUND(D21*B22;2) for 21% VAT and =D21+D22 for the total, €486.42 with the example lines.
A calculated due date
=IF(D5="";"";D5+D6) adds the payment terms to the invoice date: 26 November 2026. A sentence below joins text and cells with &.
Validation
Quantity and unit price refuse anything that isn't a number of 0 or more, with a message.
Print setup and metadata
A4 portrait, print range A1:D26, a footer line, and the description "Free sample from 99helpers.com/file-types/ots" in meta.xml.

All sample OTS files

Invoice template
sample-invoice.ots · 27.9 KB (28,529 bytes)
A one-page invoice: input cells in a cell style, locked formula cells on a protected sheet (no password), formulas for amounts, VAT, total and due date, validation and a print range.
- Checking that an app creates a new spreadsheet from a template
- Testing formulas and sheet protection in converters
Download
The same invoice as an ODS
sample-invoice.ods · 27.8 KB (28,514 bytes)
Saved from the same Calc document as the OTS. Only the mimetype entry and the manifest's root entry differ.
- Comparing a template with a spreadsheet
- Testing code that must tell OTS from ODS
Download
Blank 12-month budget template
sample-budget.ots · 26.3 KB (26,887 bytes)
Income and expense categories by month with no values: row and column totals, a balance that turns red when negative (conditional formatting), a savings rate, three named ranges and a second sheet that uses them.
- Testing conditional formatting and named ranges
- Converting a template to XLTX
Download
Minimal OTS, three entries
sample-minimal.ots · 967 bytes
Only mimetype, content.xml and META-INF/manifest.xml, written by hand: one empty input cell and one formula. It's the file shown in the anatomy above.
- Parser tests: don't assume optional parts exist
- Checking detection by the mimetype entry
Download

Ways to test with them

File type detection: all four start with PK and have mimetype at byte 30. Read from byte 38: the three OTS files say …spreadsheet-template, the ODS says …spreadsheet followed by other data.
New file, not the template: opening sample-invoice.ots should give an untitled spreadsheet. An app that saves over the template has a bug.
Formulas in conversion: convert sample-invoice.ots to XLSX or XLTX and check the total is still €486.42 and the due date still 26 November 2026.
Protection and validation: in the converted file, try typing over a total and typing text into a quantity. Both should be refused.
Defensive parsing: sample-minimal.ots has no styles.xml, meta.xml or settings.xml. Code that assumes they exist will fail on it.

Free to use for testing, teaching and demos, commercially or not, with no attribution needed. A link back to this page is always appreciated.

Put it online

Have an OTS file? Give it a link.

Drop a LibreOffice spreadsheet template on 99helpers and it gets its own link, ready to share with your team. Browsers can't display OTS files, so visitors download it and open it in LibreOffice Calc, which starts a new spreadsheet from it.

Put an OTS file online

Questions

OTS files, frequently asked

What is an OTS file?

An OpenDocument spreadsheet template, the template format of LibreOffice Calc. Opening it creates a new, untitled spreadsheet with the template's sheets, formulas and styles.

What's the difference between OTS and ODS?

Inside, only the type in the mimetype entry and the manifest: …spreadsheet-template instead of …spreadsheet. In use, an ODS opens itself, while an OTS starts a new spreadsheet.

How do I open an OTS file?

With LibreOffice Calc or another ODF spreadsheet app such as Apache OpenOffice. Double-clicking it creates a new spreadsheet from it.

How do I edit an OTS template?

In LibreOffice, open File, Templates, Manage Templates, right-click the template and choose Edit. Make the changes and save.

Can Excel open OTS files?

Excel works with ODS spreadsheets. For a template, convert it in LibreOffice to XLTX, or create a spreadsheet from it and save that as XLSX.

How do I convert an OTS to XLSX or XLTX?

In LibreOffice, save it as Excel 2007-365 Template (.xltx), or create a spreadsheet from it and save that as XLSX. On a server: soffice --headless --convert-to xlsx file.ots.

Why can't I type in some cells?

The template protects its formula cells. Type in the input cells; if you made the template, switch protection off with Tools, Protect Sheet.

Can an OTS file contain macros?

Yes. OTS has no separate macro-free extension. LibreOffice blocks unsigned macros by default; keep that setting for templates you didn't make.

Related formats

Other file types explained

ODS file XLTX file XLT file XLTM file OTT file OTP file XLSX file All file types

Keep going

Host an OTS file

Put a LibreOffice spreadsheet template online at its own address.

Share an OTS file

Send a template as a link instead of an attachment.

Host a report

Publish the finished figures people can open from a link.

Sources

Last reviewed 27 October 2026.