Kusto (KQL) Language Support for VS Code

Support for the Kusto Query Language (KQL) in Visual Studio Code. KQL is used in Azure Monitor, Azure Data Explorer, Microsoft Sentinel, and Microsoft Fabric. Includes syntax highlighting and the ability to run queries directly against an Azure Data Explorer cluster.

Features

• Syntax highlighting for .csl, .kusto, and .kql files
• Tabular operators: where, summarize, project, project-away, join, union, extend, render, parse, mv-apply, evaluate, and more
• Scalar functions: string, math, datetime, geo, IP, array, dynamic bag functions (500+)
• Aggregation functions: count, dcount, sum, avg, percentile, make_list, make_set, and more
• Data types: bool, datetime, dynamic, guid, int, long, real, string, timespan
• Comment toggling (// line comments, /* */ block comments)
• Bracket matching and auto-closing pairs for {}, [], ()
• Code folding via // #region / // #endregion markers
• Smart indentation inside {} blocks
• Run queries against an Azure Data Explorer (Kusto) cluster without leaving VS Code
• Supports Azure CLI, interactive browser, and managed identity authentication

Example

// Query the last hour of errors from AppTraces
let timeRange = 1h;
AppTraces
| where TimeGenerated > ago(timeRange)
| where SeverityLevel >= 3
| summarize ErrorCount = count(), LastSeen = max(TimeGenerated) by Message
| order by ErrorCount desc
| take 20

File Associations

The extension activates automatically for files with these extensions:

Extension	Description
.kql	KQL query files
.kusto	Kusto query files
.csl	Kusto control sequence files

To manually set the language for an open file, use the Select Language Mode command (Ctrl+K M) and choose Kusto.

Run Kusto Queries

You can execute Kusto queries directly from VS Code against an Azure Data Explorer (Kusto) cluster. Results are displayed in the Kusto Results output panel.

Prerequisites

• VS Code 1.75.0 or later
• An Azure Data Explorer cluster you have access to
• For AzureLogin mode (default): the Azure CLI installed and signed in

Step 1 — Configure the Extension

Open Settings (Ctrl+, / Cmd+,) and search for kusto, or add the following to your User or Workspace settings JSON (settings.json):

{
    // Required: the full URL of your Azure Data Explorer cluster
    "kusto.clusterUrl": "https://mycluster.kusto.windows.net",

    // Required: the database to run queries against
    "kusto.database": "MyDatabase",

    // Optional: authentication method (default: AzureLogin)
    // Options: "AzureLogin" | "InteractiveLogin" | "ManagedIdentity"
    "kusto.loginMode": "AzureLogin"
}

Tip: Use workspace settings (.vscode/settings.json) to keep cluster details local to a specific project, keeping your global User settings clean.

Step 2 — Authenticate

Choose the authentication method that fits your environment:

Login Mode	When to Use	Setup Steps
AzureLogin (default)	Local development with Azure CLI	Run az login in a terminal once
InteractiveLogin	No Azure CLI; browser available	No setup — a browser window opens automatically
ManagedIdentity	Azure-hosted VMs / containers	Ensure a system-assigned managed identity is enabled on the host

For AzureLogin (recommended for local development):

# Sign in to Azure once — the extension reuses these credentials
az login

# If you have multiple subscriptions, set the one that contains your cluster
az account set --subscription "<subscription-name-or-id>"

Step 3 — Write and Run a Query

1. Create or open a file with the .kusto, .kql, or .csl extension.

2. Write your Kusto query, for example:

   StormEvents
   | where StartTime >= ago(7d)
   | summarize Count = count() by EventType
   | order by Count desc
   | take 10

3. Run the query using any of these methods:

   Method	Action
   Keyboard shortcut	Ctrl+Alt+E (Cmd+Alt+E on macOS)
   Editor toolbar	Click the ▶ button in the top-right of the editor
   Right-click menu	Right-click in the editor → Kusto: Run Query
   Command Palette	Ctrl+Shift+P → type Kusto: Run Query

4. Results appear in the Kusto Results output channel at the bottom of the editor.

Configuration Reference

Setting	Type	Default	Description
kusto.clusterUrl	string	""	Full URL of the Azure Data Explorer cluster, e.g. https://mycluster.kusto.windows.net
kusto.database	string	""	Name of the database to run queries against
kusto.loginMode	string	"AzureLogin"	Authentication method: AzureLogin, InteractiveLogin, or ManagedIdentity

Troubleshooting

"Kusto cluster URL is not configured"
Set kusto.clusterUrl in Settings and make sure it is not empty.

"Kusto database is not configured"
Set kusto.database in Settings and make sure it is not empty.

Authentication errors with AzureLogin
Run az login in a terminal. If you have multiple tenants, use az login --tenant <tenant-id>.

"Forbidden" / 403 errors
Your account does not have the required permissions on the cluster or database. Ask your cluster administrator to grant you at minimum the Viewer role on the target database.

Bugs & Contributions

Found a bug or have a feature request? Open an issue in the GitHub repository.

Pull requests are welcome!