Free online OST to VCF converter

Contacts stored in an Outlook OST cache are not directly usable by many phones, address books, and contact-management applications. Converting them to VCF creates portable vCards that can be imported, shared, edited, or transferred between compatible systems.

What the OST format is

OST, or Offline Storage Table, is an Outlook data file used to cache mailbox content locally so Outlook can work with Exchange, Microsoft 365, or some IMAP accounts while connected intermittently or offline. Outlook creates and maintains the file automatically; it is normally found under the user profile rather than selected manually for export.

An OST can contain email, contacts, calendars, tasks, and folder data, but it is tied to the Outlook profile and account that created it. An orphaned OST may not open after the original account or profile is removed. The file may also be encrypted or partially synchronized, so it is not equivalent to an independent PST archive.

What the VCF format is

VCF, also called vCard, is a text-based contact format defined by the vCard specification. A VCF file can contain one or multiple contact records with fields such as name, organization, phone number, email address, postal address, website, notes, and photographs.

Phones, email clients, desktop address books, CRM systems, and operating systems commonly support vCards. VCF is preferable when contacts must be transferred between unrelated applications because it preserves contact fields more directly than a spreadsheet, while allowing one file to contain either a single contact or a collection of contacts.

How to actually convert OST to VCF

Use the online converter

1. Open the OST-to-VCF converter on 101convert.com.
2. Select the source .ost file and start the conversion.
3. Download the resulting .vcf file when processing finishes.
4. Import the VCF into the destination application using its contact import command, such as Contacts → Import or File → Import.

This method does not require Outlook or other installed software. The converter must be able to read the contacts in the OST; an encrypted, damaged, incomplete, or profile-dependent file may not produce usable contact records.

Use Outlook and a local contact application

1. Open the OST through the Outlook profile that owns it. If Outlook reports that the file cannot be opened, the OST may be orphaned rather than directly recoverable.
2. Open People or Contacts and verify that the required contacts are present and fully synchronized.
3. For a bulk export, choose File → Open & Export → Import/Export → Export to a file → Comma Separated Values, select the Contacts folder, and save a .csv file.
4. Import the CSV into an address-book application that supports vCard export. Thunderbird can import the CSV through Address Book → Tools → Import, after which contacts can be selected and exported as .vcf using Tools → Export or the available vCard export command.
5. Open several resulting VCF records in a text editor or the destination address book and check names, phone numbers, email addresses, and character encoding before deleting the CSV or OST copy.

For a small number of contacts, Outlook can also expose individual records through Forward → As a Business Card; save the attached vCard instead of using a bulk export.

Quality, compatibility, and limitations

• The conversion extracts contact data only. Messages, calendar items, tasks, rules, folders, and Outlook-specific metadata do not become VCF records.
• CSV is an intermediate format, so fields that have no matching column can be lost. Photos, multiple addresses, custom fields, categories, distribution lists, and contact notes require verification after export.
• VCF versions differ. Older applications commonly expect vCard 2.1, while newer systems generally support vCard 3.0 or 4.0; encoding and field support can vary between phones and mail clients.
• If the OST has not finished synchronizing, contacts missing from the local cache cannot be exported. Connect Outlook to the account and wait for synchronization before conversion.
• OST files can contain private contact and mailbox data. Use a local workflow for confidential records, or remove the source file from the conversion service after processing if the service provides that option.