Guide

What is a .cube file?

Updated November 4, 2026

A .cube file is the most widely supported LUT format in video. It's plain text, so you can open one in any text editor and see exactly what it does. Here's how to read it, what the numbers mean, and what to do when one won't load.

What a LUT does

LUT stands for lookup table. Instead of running a formula on every pixel, the editor looks each input color up in the table and replaces it with the stored output color. Colors that fall between table entries are interpolated from their neighbors. That's why a LUT is fast and predictable, and also why it can't adapt to your scene: the same input always gives the same output.

What's inside a .cube file

The format was published by Adobe as the Cube LUT specification. A small 3D LUT looks like this:

# Comments start with a hash
TITLE "Example look"
LUT_3D_SIZE 33
DOMAIN_MIN 0.0 0.0 0.0
DOMAIN_MAX 1.0 1.0 1.0
0.000000 0.000000 0.000000
0.031250 0.000000 0.000000
0.062500 0.000000 0.000000
...

• TITLE is an optional name.
• LUT_3D_SIZE (or LUT_1D_SIZE) says what kind of table it is and how many points it has per axis.
• DOMAIN_MIN and DOMAIN_MAX are optional and give the input range. When they're missing, the range is 0 to 1.
• Data lines follow: one red, green, blue triplet per line. In a 3D LUT, red changes fastest, then green, then blue, so the first lines step through red while green and blue stay at 0.

1D vs 3D LUTs

• A 1D LUT maps each channel on its own: a curve for red, one for green, one for blue. It can change brightness, contrast, and per-channel balance, but it can't move one hue toward another, so it can't do most film looks.
• A 3D LUT maps every combination of red, green, and blue to a new color, so it can shift a hue, soften saturated colors, or warm skin without warming the sky. Creative looks are almost always 3D LUTs.

What 17, 33, and 65 mean

The LUT size is the number of points along each axis of the cube. A 3D LUT with size N has N × N × N entries:

Bigger isn't automatically better. For smooth creative looks, 33 points is usually indistinguishable from 65 once interpolation fills the gaps, and it loads in more places.

How to open and check one

• Read it: open it in any plain-text editor (TextEdit in plain-text mode, Notepad, VS Code) to see the header and size.
• See what it does: load it in the free LUT previewer with a still from your own footage. It runs in your browser, so nothing is uploaded.
• Use it: every major editor accepts .cube files. Step-by-step instructions are in How to use a LUT in any editor.

When a .cube file won't load

• The download is still zipped. Unzip it first; editors won't read a .cube inside a .zip.
• It isn't really a .cube file. Other LUT formats exist (such as .3dl, .look, and .csp). Renaming a file doesn't convert it.
• The size isn't supported. Some apps, phones, and monitors only accept certain sizes, often 17 or 33. Try a 33-point version if one is available.
• The line count is wrong. A 3D LUT needs exactly N × N × N data lines. A truncated download or a hand edit that removed lines will make it fail.
• Commas instead of periods. Numbers must use a period as the decimal point (0.5, not 0,5). Files saved by some spreadsheet tools in some regions break this.

Where Filmsilk fits

Every Filmsilk look is a standard 3D .cube file built for Rec.709 footage, in 33-point with 65-point versions available, so it works in DaVinci Resolve, Premiere Pro, Final Cut Pro, CapCut, and most other editors. If your footage is log, convert it first (here's why). You can try every look on your own frame before you buy. The Collection is $29 one-time; Filmsilk Complete is $39 and adds Studio, where you can adjust any look and export your own .cube.