| Original Format | |
| N/A | |
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ORI file format is used for identifying original and backup files. ORI extension is a generic extension appended to original files as a simplified backup procedure (for example, index.php.ori). When the original files need to be restored, ORI extension should be deleted in order to use such file.
Windows
| .ab | Google Android Debug Bridge Backup Format |
| .aba | Palm Address Book Archive Format |
| .abbu | Apple Address Book Archive Format |
| .abf | Adobe Binary Screen Font Format |
| .abk | Ability Write Backup Format |
| .acp | Alfresco Exported Repository Format |
| .adi | Active@ Disk Image Format |
| .aea | Ae Timer Alarm Document Format |