> ## Documentation Index > Fetch the complete documentation index at: https://docs.gcore.com/llms.txt > Use this file to discover all available pages before exploring further. # Build a FastEdge HTTP application export const MethodSection = ({children}) => children ?? null; export const MethodSwitch = ({children}) => { const tabs = React.Children.toArray(children).map(c => { if (!c || !c.props) return null; if (c.props.id) return c; const inner = c.props.children; if (inner && inner.props && inner.props.id) return inner; return null; }).filter(Boolean); const firstId = tabs.length > 0 ? tabs[0].props.id : ""; const [active, setActive] = React.useState(firstId); React.useEffect(() => { try { const saved = localStorage.getItem("gcore_docs_method"); if (saved && tabs.find(t => t.props.id === saved)) { setActive(saved); } } catch (_) {} }, []); React.useEffect(() => { try { document.querySelectorAll("h2[id], h3[id]").forEach(heading => { const visible = heading.offsetParent !== null; document.querySelectorAll(`a[href="#${heading.id}"]`).forEach(link => { if (link.closest("h1,h2,h3,h4,h5,h6")) return; const li = link.closest("li"); if (li) li.style.display = visible ? "" : "none"; }); }); } catch (_) {} window.dispatchEvent(new Event("scroll")); }, [active]); const handleClick = id => { setActive(id); try { localStorage.setItem("gcore_docs_method", id); } catch (_) {} }; return

{tabs.map(tab => { const isActive = active === tab.props.id; return ; })}

{tabs.map(tab =>

{tab.props.children}

)}

; }; FastEdge HTTP applications respond to HTTP requests directly from the edge. The handler compiles to a WebAssembly binary and runs without servers or containers. Three language options are available — complete the toolchain setup first: [Rust (Modern HTTP)](/fastedge/getting-started/setup-rust-modern), [Rust (Legacy HTTP)](/fastedge/getting-started/setup-rust-legacy), or [JavaScript](/fastedge/getting-started/setup-javascript). ## Write a handler Each language uses a different entry point convention. Choose the tab that matches the toolchain set up earlier. Replace `src/lib.rs` with: ```rust theme={null} use wstd::http::body::Body; use wstd::http::{Request, Response}; #[wstd::http_server] async fn main(request: Request) -> anyhow::Result> { let url = request.uri().to_string(); Ok(Response::builder() .status(200) .header("content-type", "text/plain;charset=UTF-8") .body(Body::from(format!("Request received: {url}")))?) } ``` Replace `src/lib.rs` with: ```rust theme={null} use fastedge::body::Body; use fastedge::http::{Request, Response, StatusCode, Error}; #[fastedge::http] fn main(request: Request) -> Result, Error> { let url = request.uri().to_string(); Response::builder() .status(StatusCode::OK) .header("content-type", "text/plain;charset=UTF-8") .body(Body::from(format!("Request received: {url}"))) } ``` Create `src/index.js`: ```js theme={null} addEventListener('fetch', (event) => { const url = event.request.url; event.respondWith(new Response(`Request received: ${url}`)); }); ``` ## Build Compile the handler to a WebAssembly binary. The first build downloads dependencies and takes one to two minutes. ```sh theme={null} cargo build --release --target wasm32-wasip2 ``` The binary is at `./target/wasm32-wasip2/release/hello_world.wasm`. ```sh theme={null} cargo build --release --target wasm32-wasip1 ``` The binary is at `./target/wasm32-wasip1/release/hello_world.wasm`. ```sh theme={null} npx fastedge-build --input src/index.js --output wasm/app.wasm ``` The binary is at `./wasm/app.wasm`. ## Deploy 1. In the [Gcore Customer Portal](https://portal.gcore.com), navigate to **FastEdge** > **HTTP Applications** > **Applications** and click **Create new application**. 2. Click **Upload binary** and select the `.wasm` file produced in the Build step. 3. Enter a **Name** for the application. 4. Click **Save and deploy**.

The application URL appears on the details page. Test it:

```sh theme={null} curl -i https://-.fastedge.app/hello ```

Deploying requires two API calls: upload the binary to get its ID, then create the application. An [API token](/account-settings/api-tokens) is required.

```bash theme={null} export GCORE_API_KEY="{YOUR_API_KEY}" ``` Do not commit API keys to source control. **1. Upload the binary** ```bash theme={null} curl -sX POST 'https://api.gcore.com/fastedge/v1/binaries/raw' \ -H "Authorization: APIKey $GCORE_API_KEY" \ -H 'Content-Type: application/octet-stream' \ --data-binary "@./target/wasm32-wasip2/release/hello_world.wasm" ``` ```bash theme={null} curl -sX POST 'https://api.gcore.com/fastedge/v1/binaries/raw' \ -H "Authorization: APIKey $GCORE_API_KEY" \ -H 'Content-Type: application/octet-stream' \ --data-binary "@./target/wasm32-wasip1/release/hello_world.wasm" ``` ```bash theme={null} curl -sX POST 'https://api.gcore.com/fastedge/v1/binaries/raw' \ -H "Authorization: APIKey $GCORE_API_KEY" \ -H 'Content-Type: application/octet-stream' \ --data-binary "@./wasm/app.wasm" ```

The response contains the binary ID:

```json theme={null} {"id": 4695, "api_type": "wasi-http", "status": 1} ``` **2. Create the application** ```bash theme={null} export BINARY_ID=4695 curl -sX POST 'https://api.gcore.com/fastedge/v1/apps' \ -H "Authorization: APIKey $GCORE_API_KEY" \ -H 'Content-Type: application/json' \ -d "{\"name\": \"my-http-app\", \"binary\": $BINARY_ID, \"status\": 1}" ```

The response contains the application URL:

```json theme={null} {"name": "my-http-app", "url": "https://my-http-app-1000503.fastedge.app", "api_type": "wasi-http"} ``` **3. Test**

The URL becomes active within a few seconds:

```bash theme={null} curl -i https://my-http-app-1000503.fastedge.app/hello ```