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docs/md/how_to/javascript/virtual_server.md

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+# Virtual Servers
+
+Perspective's Virtual Server feature lets you connect `<perspective-viewer>` to
+external data sources without loading data into Perspective's built-in engine.
+Instead, queries are translated and executed natively by the external database.
+
+For a detailed explanation of how virtual servers work, see the
+[Virtual Servers](../../explanation/virtual_servers.md) concepts page.
+
+Perspective ships with built-in virtual server implementations for:
+
+- [**DuckDB**](./virtual_server/duckdb.md) — query DuckDB databases in-browser
+  via `@duckdb/duckdb-wasm`, or on the server via Node.js.
+- [**ClickHouse**](./virtual_server/clickhouse.md) — query a ClickHouse server
+  directly from the browser or from Node.js.
+
+You can also [**implement your own**](./virtual_server/custom.md) virtual server
+to connect Perspective to any data source by implementing the
+`VirtualServerHandler` interface.