OST File — Open & Convert .ost Online
What Is a .ost File?
OST (.ost) is a email file format. OST is an offline Outlook data file for Exchange accounts. Created by Microsoft, this format is essential for professionals.
How to Open .ost Files
Upload your .ost file to OpenAnyFile and instantly read and archive it in your browser. No software installation required. Works on Windows, macOS, Linux, iPhone, and Android.
Everything About OST Files
Popular OST Conversions
Frequently Asked Questions
What is a .ost file?
A .ost file is a email format called OST. OST is an offline Outlook data file for Exchange accounts.
How do I open a .ost file without installing software?
Upload your .ost file to OpenAnyFile. Our browser-based tool instantly detects and displays it — no downloads needed.
What program creates .ost files?
.ost files are typically created by Microsoft.
Can I convert .ost to another format?
Yes. OpenAnyFile converts .ost to PST, EML, MSG.
Is it safe to open .ost files online?
Yes. OpenAnyFile processes files in a secure, isolated environment. Files are automatically deleted and all transfers use HTTPS.
Can I open .ost on my phone?
Yes. OpenAnyFile works on all mobile browsers including iPhone and Android.