A file with an .ODS file extension is most likely an OpenDocument Spreadsheet file that contains spreadsheet information such as text, charts, images, formulas and numbers, all placed within cell boundaries filled with cells.
The Outlook Express 5 Mailbox file also uses the ODS file extension, but to store e-mail messages, newsgroups, and other e-mail settings; they have nothing to do with spreadsheet files.
How to open an ODS file
The OpenDocument Spreadsheet file can be opened with a free Calc program that comes as part of the OpenOffice package. Included in the suite are several other applications such as a word processor called Writer and a presentation program called Impress.
You get all OpenOffice programs when you download the suite, but you can choose which one to install (ODS files are only relevant in Calc).
LibreOffice (Calc section) and Calligra Suite are two other suites that are similar to OpenOffice which can open ODS files too. Microsoft Excel also works, but it’s not free.
What is LibreOffice?
If you use a Mac, some of the above programs work to open ODS files, but so does NeoOffice.
Chrome users can install the ODT, ODP, ODS Viewer extensions to open ODS files online without having to download them first.
Whatever operating system you use, you can upload an ODS file to Google Drive to save it online and preview it in your browser, where you can also download it to a new format (see the next section below to learn how it works).
DocsPal and Zoho Sheet online ODS viewers that you can use free. Unlike Google Drive, you don’t need to have a user account with this website to view files.
Although it’s not super useful, you can also open the OpenDocument Spreadsheet program with an unzipped file utility like 7-Zip. Doing this won’t let you see spreadsheets in the same way as in Calc or Excel but it allows you to extract embedded images and preview sheets.
You must install Outlook Express to open the ODS file associated with the program. See this Google Groups question about importing ODS files from a backup if you are in that situation but you are not sure how to get messages out of the file.
How to Convert ODS Files
OpenOffice Calc can convert ODS files to XLS, PDF, CSV, OTS, HTML, XML and a number of other related file formats. The same applies with other free ODS openers which can be downloaded from above.
If you need to convert ODS to XLSX or other file formats supported by Excel, just open the file in Excel and then save it as a new file. Another option is to use the Zamzar online ODS converter.
Google Drive is another way you can convert ODS files online. Upload the file there then right-click and choose to open it with Google Sheets. Once you have it, use the File menu> Download as on Google Sheets to save it as an XLSX, PDF, HTML, CSV or TSV file.
Zoho Sheet and Zamzar are can be used to convert ODS files online. Zamzar is unique because it can convert ODS files to DOC for use in Microsoft Word, as well as MDB and RTF.
More information about ODS files
ODS files are in the XML-based OpenDocument Spreadsheet file format, as is the XLSX file used with the MS Excel spreadsheet program. This means all files are stored in an ODS file like an archive, with folders for things like images and thumbnails, and other file types such as XML and manifest.rdf files.
ODS files is also used by Outlook Express 5, the only version of Outlook Express that uses it. Another version of the email client uses DBX files for the same purpose. ODS and DBX files are the same as PST files used with Microsoft Outlook.
Still Can’t Open Your File?
The first thing you should do if you cannot open your file with the programs mentioned above is to double-check the spelling of the file extension. Some file formats use file extensions that might look like “.ODS” but that does not mean that the format has something to do with each other or they can be opened with the same program.
One example is the ODP file. Even though the OpenDocument Presentation files are open with the OpenOffice program, they don’t open with Calc.
Another is the ODM file, which is a shortcut file that is related to the OverDrive application, but has nothing to do with the spreadsheet file or ODS file.