DDS file format (.dds)

What is a DDS file?

In short: A DDS file (.dds) is an image file in the DDS format. A DDS file holds a texture already in the block-compressed layout a graphics card expects, along with its mipmaps: progressively smaller copies used for surfaces further from the camera. It can be converted to JPG, PNG or WEBP for free in a web browser with iHateFiles, without uploading it.

Introduced by Microsoft with DirectX 7 in 1999 for storing textures in a form graphics hardware reads directly.

A DDS file holds a texture already in the block-compressed layout a graphics card expects, along with its mipmaps: progressively smaller copies used for surfaces further from the camera. Nothing has to be decoded at load time, which is why games use it.

What DDS is good at

• Uploaded to the GPU with no decoding step
• Holds the whole mipmap chain in one file
• Stays compressed in video memory

Where DDS falls short

• The block compression is lossy and shows on gradients
• Only useful in a graphics pipeline
• Nothing outside game tooling opens it

When to use DDS

Use DDS when a game engine or modding tool asks for it.

How to open a DDS file

Game engines, texture tools, and image editors with a plugin.

The thing that usually goes wrong

DDS is lossy despite feeling like a raw format, so repeatedly editing and re-saving one degrades the texture each time.

Inside a DDS file

DirectDraw Surface is not really an image format in the ordinary sense. It is a container for texture data already compressed in a scheme the graphics card understands natively — BC1 through BC7, historically called DXT. The point is that the GPU never has to decompress it: the file is uploaded to video memory in the form it was stored, and stays compressed there.

That is why every game ships them. A 2048×2048 texture as PNG occupies about 16 MB of video memory once decoded; the same texture as BC1 occupies 2.7 MB and stays that way. Across a few thousand textures that difference decides whether a game fits in memory.

A DDS also usually carries a mipmap chain — the same image at halving resolutions, all the way down to a single pixel — so the card can pick the right level of detail by distance. Converting a DDS to PNG gives you the top level and quietly discards the rest.