Set language for syntax highlighting in Visual Studio Code

In the very right bottom corner, left to the smiley there was the icon saying "Plain Text". When you click it, the menu with all languages appears where you can choose your desired language.

https://i.stack.imgur.com/XgMzj.png

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Press Ctrl + KM and then type in (or click) the language you want.

Alternatively, to access it from the command palette, look for "Change Language Mode" as seen below:

https://i.stack.imgur.com/4JCti.png

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Another reason why people might struggle to get Syntax Highlighting working is because they don't have the appropriate syntax package installed. While some default syntax packages come pre-installed (like Swift, C, JS, CSS), others may not be available.

To solve this you can Cmd + Shift + P → "install Extensions" and look for the language you want to add, say "Scala".

https://i.stack.imgur.com/PRJ4Q.png

Find the suitable Syntax package, install it and reload. This will pick up the correct syntax for your files with the predefined extension, i.e. .scala in this case.

On top of that you might want VS Code to treat all files with certain custom extensions as your preferred language of choice. Let's say you want to highlight all *.es files as JavaScript, then just open "User Settings" (Cmd + Shift + P → "User Settings") and configure your custom files association like so:

  "files.associations": {
    "*.es": "javascript"
  },

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Syntax Highlighting for custom file extension

Any custom file extension can be associated with standard syntax highlighting with custom files association in User Settings as follows.

https://i.stack.imgur.com/3fKSP.gif

Note that this will be a permanent setting. In order to set for the current session alone, type in the preferred language in Select Language Mode box (without changing file association settings)

Installing new Syntax Package

If the required syntax package is not available by default, you can add them via the Extension Marketplace (Ctrl+Shift+X) and search for the language package.

You can further reproduce the above steps to map the file extensions with the new syntax package.

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To permanently set the language syntax:
open settings.json file

format all txt files with javascript formatting

"files.associations": {
            "*.txt": "javascript"
          
     }

format all unsaved files (untitled-1 etc) to javascript:

"files.associations": {
            "untitled-*": "javascript"
          
     }

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Note that for "Untitled" editor ("Untitled-1", "Untitled-2"), you now can set the language in the settings.

The previous setting was:

"files.associations": {
        "untitled-*": "javascript"
 }

This will not always work anymore, because with VSCode 1.42 (Q1 2020) will change the title of those untitled editors.
The title will now be the first line of the document for the editor title, along the generic name as part of the description.
It won't start anymore with "untitled-"

See "Untitled editor improvements"

Regarding the associated language for those "Untitled" editors:

By default, untitled files do not have a specific language mode configured. VS Code has a setting, files.defaultLanguage, to configure a default language for untitled files. With this release, the setting can take a new value {activeEditorLanguage} that will dynamically use the language mode of the currently active editor instead of a fixed default. In addition, when you copy and paste text into an untitled editor, VS Code will now automatically change the language mode of the untitled editor if the text was copied from a VS Code editor:

https://i.stack.imgur.com/FxqHK.gif

And see workbench.editor.untitled.labelFormat in VSCode 1.43.

In March 2021 (possible for VSCode 1.55), issue 118455 "Automatic language classification for Untitled files" and PR 119325 are studying some kind of automatic language detection for untitled files.

And if you forget, with VSCode 1.56, Apr. 2021:

Untitled editors hint

We have noticed that many new users are not aware that a language has to be set in order to get full VS Code language support. To help with this problem, we have introduced a hint for untitled editors to help users set the correct language mode. The untitled hint might not be helpful to advanced users, so it goes away immediately as you start typing or you can select don't show to never display the hint again.

With VScode 1.60 (Aug. 2021):

Automatic language detection

Last release, we introduced an experimental feature for untitled files that would automatically set the language mode for the file based on the contents. This feature uses machine learning to guess the language and is done entirely on your machine. It's powered by the open-source ML library, Tensorflow.js, and the ML model from Guesslang by GitHub user @yoeo. This release we are enabling this feature by default and also expanding the automatic language detection to files that don't have a file extension. In Notebooks, we provide an easy way to ask for language detection using the language picker. This enables a few fun scenarios: Grab an example from online and paste it in an untitled editor Language detection of untitled files "Pipe into code" language detection (showing off detection of extension-less files) Language detection of extension-less files Auto detect option in Notebooks language picker Language detection of Notebooks

VSCode 1.65 (Feb. 2022) comes with:

Improved automatic language detection When the new setting workbench.editor.historyBasedLanguageDetection is enabled, untitled editors will use an improved automatic language detection algorithm that factors in your editor history and the contents of the current workspace to provide detection results with much less input text required than before. Below is an example of using this across JavaScript, TypeScript, Markdown, PHP, and C++ (many more languages are supported): Theme: GitHub Light + HC Customizations

VSCode 1.70 (July 2022) will propose (issue 152920, PR 153872)

Provide a command to create a new untitled file with a specific language set Allow to specify language id in command to create a new untitled file The registerCommandAndKeybindingRule allows for "New Untitled File args" to add the language ID if known.

That allows for links like [Create Python File](command:toSide:workbench.action.files.newUntitledFile?<args>) which would create a new untitled file directly for Python language.

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Now you can set syntax highlight from command palette by installing an VS Code extension: Set Syntax

https://i.stack.imgur.com/Ig5q6.png

https://marketplace.visualstudio.com/items?itemName=ahgood.set-syntax

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You can change the language mode in VS Code as follows.

Select the file which you want to change then use the following shortcut.

On macOS:

press ⌘+K then press M.

On Windows and Linux:

press CTRL+K then press M

Select the language from the list provided or choose Auto-detect

https://i.stack.imgur.com/UpOpX.png

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This may not be quite a correct answer to the question, but this is what happened to me. Sometimes the answer that we seek may not be the answer that we needed.

https://i.stack.imgur.com/xig4M.gif

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