.KT file extension
To open .KT files on Windows, install and open IntelliJ IDEA or Android Studio.
To open a .kt file, use a Kotlin-capable IDE/editor such as IntelliJ IDEA or Android Studio. You can also view and edit it as plain text in many code editors, but IDE support helps with syntax highlighting, navigation, and building.
Last updated: June 12, 2026
Open on your device
Choose your operating system for a dedicated step-by-step opening guide.
How to open .KT files
Use these platform-specific instructions to open .KT files safely.
Windows
- Install and open IntelliJ IDEA or Android Studio.
- Use File → Open and select the folder/project containing the .kt file (recommended), or open the .kt file directly for viewing/editing.
Mac
- Install and open IntelliJ IDEA or Android Studio.
- Open the project that contains the .kt file (preferred), then open the .kt file from the Project view.
Linux
- Install and open IntelliJ IDEA (or another Kotlin-supporting editor/IDE).
- Open the project folder containing the .kt file, then open the file in the editor with Kotlin support enabled.
iOS
- There is no common iOS-native workflow for building Kotlin projects directly from a .kt file; use a desktop IDE to open and work with it, or view it as plain text in a text viewer app.
Android
- If you received a .kt file on Android, you can usually only view it as plain text in a file/text viewer; for proper Kotlin editing and building, transfer it to a computer and open it in Android Studio or IntelliJ IDEA.
Security notes
- .kt files are plain-text source code, but they can contain code that does harmful things if you compile and run it; do not build/run untrusted Kotlin projects.
- Be cautious with projects that include build scripts and dependencies: opening a single .kt file is usually safe as text, but executing project tasks (build/run) can trigger downloads and code execution in the build environment.
- If a .kt file comes from an unknown source, treat it as untrusted code: review it before compiling, and prefer opening it in read-only mode if you only need to inspect it.
Before you run downloaded code
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Can't open this file?
These are the most common causes and fixes when .KT files fail to open.
Common reasons
- The file opens in the wrong app or shows as plain text without Kotlin features
- Kotlin code has errors because imports/dependencies cannot be resolved
- The file extension is misused and the content is not Kotlin source
Fix steps
- Open the containing project/folder in IntelliJ IDEA or Android Studio instead of opening only the file.
- Set your file association to your preferred editor/IDE if you want .kt to open there by default.
OS-specific troubleshooting
What is a .KT file?
A .kt file is a plain-text source file written in the Kotlin programming language. It can include Kotlin declarations such as packages, imports, classes, functions, and top-level code. Kotlin projects commonly compile .kt sources into JVM bytecode (and in Android builds) using standard Kotlin toolchains integrated into IDEs.
Background
The .kt extension is the standard filename extension for Kotlin source code files. Kotlin is a statically typed programming language that is widely used for application development, including Android development, and for general-purpose JVM programming.
In practice, .kt files are edited inside an IDE that understands Kotlin syntax and project structure. IntelliJ IDEA and Android Studio are commonly used because they provide Kotlin-aware editing features and build/run integration.
Because .kt files are plain text, they are also frequently used in version control systems and code review tools. When shared, they are usually part of a larger Gradle/IDE project rather than standalone documents.
Further reading
Authoritative resources for more details on the .KT format.
- Kotlin (Wikipedia) — file extensions and overview
- Kotlin language specification (kotlinlang.org) — examples using .kt files
- IDEs for Kotlin development (Kotlin Documentation)
- FileInfo: KT File — Kotlin Source Code File
- IANA Media Types registry (to verify registered MIME types)
- Shared MIME-info Database specification (freedesktop.org)
Common .KT issues
The file opens in the wrong app or shows as plain text without Kotlin features
Operating systems may not associate .kt with a Kotlin IDE, or you may be opening a single file outside its project so the IDE cannot resolve dependencies.
- Open the containing project/folder in IntelliJ IDEA or Android Studio instead of opening only the file.
- Set your file association to your preferred editor/IDE if you want .kt to open there by default.
Kotlin code has errors because imports/dependencies cannot be resolved
A .kt file often relies on other source files and build configuration from its project; opening it alone can cause unresolved references.
- Obtain the full project (not just the .kt file) and open the project in the IDE.
- If the project uses a build system, let the IDE finish project sync/indexing so it can download/resolve dependencies.
The file extension is misused and the content is not Kotlin source
While .kt is commonly used for Kotlin source, a file may be mislabeled or unrelated; it may not contain valid Kotlin code.
- Open the file in a plain-text editor to confirm it contains Kotlin code (e.g., package/import statements, Kotlin syntax).
- If it is not Kotlin, ask the sender for the correct file type or the correct project/context.
FAQ
Is a .kt file just text?
Yes. A .kt file is a plain-text Kotlin source file. IDEs add features like syntax highlighting and code navigation, but the file itself is text.
What program should I use to open and edit .kt files?
IntelliJ IDEA and Android Studio are commonly used for Kotlin development and can open and edit .kt files with full language support.
Can I run a .kt file by double-clicking it?
Typically no. A .kt file is source code; to run it you normally need the surrounding project/tooling to compile it and execute the result (for example through an IDE or a build process).
Why does the .kt file show errors when I open it?
Many .kt files depend on other source files and libraries. Open the full project in a Kotlin IDE so dependencies and project configuration can be resolved.
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