Top 5 Free OST Viewer Tools to Open & Read OST File

Sometimes, you may be stuck in a situation wherein you want to view an Outlook Offline Data File (.ost) but cannot do so. For instance, you might not be able to view an OST file shared by a user, as you don’t have Outlook installed on your system. Or, you might not be able to access your OST file, as it has become inaccessible or corrupt. Whatever be the reason, you can easily view .ost files by using an OST file viewer tool. It allows viewing OST file contents directly from the tool’s interface.  

However, with too many OST file viewer tools available, finding the right one may require a lot of your time and effort. To help you out, we have researched and compared the ‘top 5 OST file viewer’ that can help you open and read an OST file for free. 

  1. Stellar Viewer for OST


Coming from one of the most trusted data care brands in the world, Stellar Viewer for OST can scan Outlook OST data file of any size and shows the entire email data it contains. The USP of the software is its simple to use, intuitive graphical user interface (GUI) that can be easily operated by any user to scan and open .ost files without technical assistance. For saving entire OST file data or an orphaned/encrypted OST file, you can register for OST to PST Converter Software.

Supported OS: Windows 10, 8, 7, Vista, XP.


  • Allows to open and view OST files without Outlook and Exchange server.
  • Allows to open and scan corrupt or damaged OST files.
  • Option to search for particular mails. 
  • Previews each and every item stored in an OST file, including emails, calendar, contacts, tasks, notes, and journals. 
  • Helps view mail data by ‘subject line’, ‘From’, ‘To’, ‘CC’, ‘BCC’, and other details.
  • Allows saving individual emails in multiple file formats like EML, MSG, RTF, HTML, and PDF for free.
  • Maintains folder hierarchy of OST file’s mailbox.


  • Technical support for freeware option is not available.

2. Aryson OST Viewer


Aryson OST Viewer is also an effective tool that makes it easy to view and open OST file contents without Outlook. It helps view emails and other mail items from all kinds of Offline data files. 

Supported OS: Windows 10, 8, 7, and below versions.


  • Allows viewing normal and corrupt OST file emails, along with attachments.
  • Scans severely corrupt OST files by using 3 recovery modes: Standard, Advanced & Deep options.
  • Shows preview of all OST file items such as emails, attachments, tasks, notes, contacts, etc.
  • Allows saving the log of OST file items.
  • Searches OST file from local system. 


  • Saves data in HTML file format only.
  • Only allows viewing emails from a corrupt OST file.

3. MailsDaddy Free OST Viewer


MailsDaddy Free OST Viewer is another free tool to view OST file contents. This OST reader application allows viewing all components of Outlook Offline data file like emails, contacts, calendars, tasks, journals, etc.

Supported OS: Windows 10, 8.1, 8, 7, Vista, and older versions.


  • Helps open OST file without Outlook or Exchange server.
  • Allows to open and view the content of corrupt or orphaned OST files.
  • Previews OST file content with all mail properties like ‘To’, ‘CC’, ‘BCC’, ‘From’, etc.
  • Option to search for all files with .ost extension.
  • Preserves the original folder hierarchy of Offline data file.


  • Free version of the software does not allow saving OST files.

4. SysTools OST Viewer Freeware


SysTools OST Viewer Freeware is another great tool that provides free preview of OST file data such as emails, contacts, calendars, etc. The free version of the tool can be installed on multiple computers.

Supported OS: Windows 10, 8.1, 8, 7 and Vista 


  • Helps open and view OST files without any dependency on any email client.
  • Allow to view corrupt or orphaned OST file via advanced scan mode.
  • Previews OST file contents.
  • Allows viewing emails with attachments.
  • Sort emails based on different parameters like ‘From’, ‘Company’, ‘Location’, ‘Subject’, etc.


  • Does not allow to save previewed OST file emails.
  • Option to search specific emails is available in the paid version.

5. Kernel OST Viewer


OST Viewer from Kernel is another great tool that helps users to open and read Offline data files (.ost). It allows opening of all OST file items including emails, attachments, contacts, calendar, etc. The tool helps add and view multiple OST files.

Supported OS: Windows 10, 8.1, 8, 7, Vista, and lower versions.


  • Opens an OST file without Outlook or Exchange account.
  • Can read corrupt OST file.
  • Helps locate and preview specific OST email items.
  • Allows viewing email data by using filters like ‘Date’, ‘From’, ‘To’, etc.
  • Allows opening email attachments.
  • Previews data with original properties and structure.


  • Only allows saving a list of emails in HTML file format. 

Check out the below table that summarizes the features of the top 5 free OST File Viewer Tools. 

Software/Features Stellar OST Viewer Aryson OST Viewer MailsDaddy Free OST Viewer SysTools OST Viewer Freeware Kernel OST Viewer
Open & Scan Corrupt OST File Yes Yes Yes Yes Yes
View Corrupt OST File Yes Yes  Yes Yes Yes
Option to Find Specific OST Mails Yes Yes Yes No Yes
Previews all Mail Contents Yes Yes Yes Yes Yes
Preserves Folder Hierarchy Yes Yes Yes Yes Yes
Saves Accessible OST File Yes Yes No No Yes
Supports Multiple File Saving Options Yes

(supports EML, MSG, RTF, HTML, and PDF formats)


(supports only HTML format)

No No No

(supports only HTML format)

Windows 10 Support Yes Yes Yes Yes Yes
Cost Free Free Free Free Free


Dharmesh is Co-Founder of TechnoFizi and a passionate blogger. He loves new Gadgets and Tools. He generally covers Tech Tricks, Gadget Reviews etc in his posts. Beside this, He also work as a SEO Analyst at TechnoFizi Solutions.


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