Convert OST to ICO
Convert OST to ICO online: cached Outlook messages laid out as readable pages, saved as a 256 × 256 ICO icon. Free, no sign-up.
Drop your OST files here
Up to 200MB per file.
Conversion Settings
Files are encrypted and auto-deleted after conversion
How to Convert
- 101
Upload your OST files
Drag and drop or select OST files from your device. You can upload multiple files at once.
- 202
Configure Output
Choose any available ICO output options, then start the conversion.
- 303
Download ICO files
Once conversion finishes, download your files individually or as a compressed ZIP archive.
Why convert OST to ICO?
Outlook keeps an OST file as an offline copy of an Exchange, Microsoft 365 or Outlook.com mailbox on your computer. The image shows the body of each message from the offline mailbox, formatted text and tables included, stacked in turn beneath an “OST mailbox” heading.
ICO output is a 256 × 256 pixel Windows icon: the image is scaled to fit with its proportions kept, and the surrounding space is transparent.
Frequently Asked Questions
How do I convert OST to ICO?
Drop your OST file above and press Convert. Our servers read the offline data file, export its messages and render them one after another as pages. The result is saved as a 256 × 256 ICO icon, ready to download.
Can I turn an OST file into ICO without Outlook installed?
Yes. The OST file is read directly on our servers, so its cached messages are laid out and rendered without Outlook or a connection to the mail server.
Which parts of each OST message are rendered in the ICO?
Each message body is rendered with its text, formatting and tables, and the messages follow one another beneath an “OST mailbox” heading.
Which part of the OST becomes the ICO icon?
The first page of the rendered content is used for the icon, fitted inside the 256 × 256 square with its proportions kept.
What size is the ICO made from a OST file?
The icon is 256 × 256 pixels, the largest standard Windows icon size. The image is fitted inside the square with its proportions kept and a transparent surround, stored as a PNG-compressed icon.
Is my .ost file kept private?
Your file is uploaded over an encrypted connection, converted on our servers and deleted automatically within 24 hours. We never read, share or keep your files, and no account is needed.