Free OST Converter
Convert to Any Format

OST (Offline Storage Table) is Microsoft Outlook's format for storing a local copy of your mailbox when you use Exchange or certain account types. The file uses the same binary structure as PST (magic bytes "!BDN") and lets Outlook work offline. OST to CSV conversion takes that offline cache and exports each email's metadata into a CSV file — a comma-separated format that Excel, Google Sheets, and databases can open for reporting and analysis.

Our free OST to CSV converter processes entirely on your device. You drop a .ost file, and the tool validates the header, scans for email-like content (From:, To:, Subject:, Date:, and body text), then generates a single CSV with one row per message. All processing is private; nothing is uploaded. This lets you turn Exchange/Outlook offline data into spreadsheet-ready data without leaving your device.

Common use cases include building contact lists from sent/received addresses, analyzing email volume or subject patterns, and importing metadata into CRM or other systems. Because the converter is private, you can use it on any operating system without installing Outlook. OST files are typically found on Windows where Outlook has been used with Exchange; converting to CSV makes the data portable and easy to analyze.

For full fidelity including attachments and rich HTML bodies, Outlook or a dedicated desktop OST tool may be needed. This tool extracts metadata and text on your device and is ideal for reporting and data export when you don't have Outlook available.