HDD Data & Text — A .hdd file is a HDD Data & Text. It is a text-based data format widely used for configuration files, data interchange and API payloads.
Quick facts
What is .hdd
A .hdd file is a HDD Data & Text. It is a text-based data format widely used for configuration files, data interchange and API payloads.
In the mime-db registry it maps to application/x-virtualbox-hdd, and it is marked as compressible. When serving .hdd over HTTP, set the Content-Type header as shown in Developer info below.
Related entities: it maps to application/x-virtualbox-hdd — and is delivered over HTTP via the Content-Type header.
How to open .hdd files
Developer info
When served over HTTP, responses should set the following header:
Content-Type: application/x-virtualbox-hdd
Common software that reads/writes .hdd:
Relation chain
Related extensions
Related MIME types
Common uses
How to edit .hdd files
How to create .hdd files
Frequently asked questions
Common options include VS Code, Notepad++, Sublime Text. You can also open many of these files with built-in viewers or a browser.
Create a new file in any text editor or the app that owns the format and save it with the .hdd extension.
application/x-virtualbox-hdd is the media type identifier used for .hdd files during network transfer (for example in the HTTP Content-Type header).
Sources & standards
Updated 2026-08-18
Explore this reference