KTX2

Khronos Texture 2.0

image/ktx2 Released 2021 · by Khronos Group

Khronos Texture 2.0 (KTX2) is a next-generation container format for GPU textures. It significantly improves upon the original KTX format by natively integrating Basis Universal compression (ETC1S and UASTC) and Zstandard (zstd) supercompression. This allows a single KTX2 file to be transcoded at runtime into the optimal compressed texture format for any target GPU (desktop or mobile), eliminating texture fragmentation.

3D & Textures Transparency ✦ HDR Production Ready

Technical Specifications

MIME Type

image/ktx2

Extensions

.ktx2

Container

KTX 2.0

Compression

Basis Universal (ETC1S / UASTC) & Zstandard (zstd) Supercompression & Uncompressed

Algorithms

ETC1SUASTCZstandard (zstd)Raw GPU Formats (ASTC, BCn)

Color Depth

8-bit, 16-bit, 32-bit (Float)

Metadata

None

Capabilities

Transparency

Animation

Progressive Loading

Alpha Channel

HDR Support

Official Specification

Magic Bytes & HTTP Headers

File Signature (Magic Bytes)

AB 4B 54 58 20 32 30 BB 0D 0A 1A 0A

ASCII: «KTX 20»\r\n\x1A\n

HTTP Headers

Content-Type: image/ktx2

HTML Accept Attribute

accept="image/ktx2, .ktx2"

Browser Support Matrix

Browser	Status	Min Version
Chrome	Not Supported	—
Firefox	Not Supported	—
Safari	Not Supported	—
Edge	Not Supported	—
Internet Explorer	Not Supported	Legacy

Advantages & Limitations

Advantages

Universal hardware compatibility: write once, transcode anywhere to the target GPU's preferred format (ASTC, BC7, PVRTC, etc.)
Drastically reduces transmission size over networks thanks to Basis Universal and Zstandard supercompression
Seamless integration with the glTF ecosystem for optimized 3D asset delivery

Limitations

Requires WebAssembly (Wasm) decoders and JavaScript loaders for web viewing, increasing initial application payload slightly
Encoding textures into high-quality Basis Universal UASTC can be computationally intensive and slow
Zero support in traditional 2D image viewers or native OS previews

Developer Code Snippets

import magic
print(magic.from_file('model_texture.ktx2', mime=True)) # May output 'image/ktx2' if magic db is updated

const FileType = require('file-type');
const type = await FileType.fromFile('model_texture.ktx2');
console.log(type?.mime); // Outputs 'image/ktx2'

import "net/http"
// Requires custom byte checking for the KTX 2.0 header: bytes.HasPrefix(buf, []byte{0xAB, 0x4B, 0x54, 0x58, 0x20, 0x32, 0x30, 0xBB, 0x0D, 0x0A, 0x1A, 0x0A})

$mime = mime_content_type('model_texture.ktx2');
echo $mime; // Standard setups will often resolve to application/octet-stream without custom magic rules

File Detection Steps

How to programmatically detect a image/ktx2 file by reading its raw bytes:

1 Check the first 12 bytes for the KTX 2.0 signature (AB 4B 54 58 20 32 30 BB 0D 0A 1A 0A)
2 Parse the Data Format Descriptor (DFD) block to determine the internal compression payload (e.g., ETC1S or UASTC)

Software Support

T

Three.js (KTX2Loader)

B

Babylon.js

B

Blender

K

Khronos toktx CLI Tool

G

Godot Engine

Conversion Tools

Share & Embed

Markdown Badge

[![KTX2 Format](https://freewebptojpg.com/mime/image/ktx2/badge.svg)](https://freewebptojpg.com/mime/image/ktx2)

Interactive iframe Widget

<iframe src="https://freewebptojpg.com/mime/image/ktx2/embed" width="100%" height="280" style="border:1px solid #cbd5e1;border-radius:8px;" title="KTX2 Specs"></iframe>

JSON API

All data on this page is available as a free, open JSON API. Use it in your project, documentation, or tooling.

GET https://freewebptojpg.com/mime/image/ktx2.json Open JSON

Free to use

No auth required

CORS enabled

Use from any domain

Cached 24h

Cache-Control headers set

Frequently Asked Questions

What is the difference between KTX and KTX2?

KTX (v1.1) stored textures in a specific hardware format (like ASTC or BCn), meaning developers often had to ship multiple versions of the same texture for different devices. KTX2 integrates Basis Universal compression, allowing a single file to be dynamically transcoded at runtime into whatever native format the host GPU prefers, vastly reducing application bundle sizes.

What is the magic byte for a KTX2 file?

KTX2 files begin with a 12-byte identifier: AB 4B 54 58 20 32 30 BB 0D 0A 1A 0A. This translates to '«KTX 20»' followed by carriage return, line feed, substitute, and line feed characters.

How is KTX2 used on the web?

While not supported natively by HTML <img> tags, KTX2 is widely used in WebGL and WebGPU applications (via engines like Three.js and Babylon.js) and is the standard highly-compressed texture format for glTF 3D models (via the KHR_texture_basisu extension).