Build and deploy
Node servers
Edit this page on GitHubTo generate a standalone Node server, use adapter-node
.
Usagepermalink
Install with npm i -D @sveltejs/adapter-node
, then add the adapter to your svelte.config.js
:
ts
importCannot find module '@sveltejs/adapter-node' or its corresponding type declarations.2307Cannot find module '@sveltejs/adapter-node' or its corresponding type declarations.adapter from'@sveltejs/adapter-node' ;export default {kit : {adapter :adapter ()}};
Deployingpermalink
First, build your app with npm run build
. This will create the production server in the output directory specified in the adapter options, defaulting to build
.
You will need the output directory, the project's package.json
, and the production dependencies in node_modules
to run the application. Production dependencies can be generated by copying the package.json
and package-lock.json
and then running npm ci --omit dev
(you can skip this step if your app doesn't have any dependencies). You can then start your app with this command:
node build
Development dependencies will be bundled into your app using Rollup. To control whether a given package is bundled or externalised, place it in devDependencies
or dependencies
respectively in your package.json
.
Compressing responsespermalink
You will typically want to compress responses coming from the server. If you are already deploying your server behind a reverse proxy for SSL or load balancing, it typically results in better performance to also handle compression at that layer since Node.js is single-threaded.
However, if you're building a custom server and do want to add a compression middleware there, note that we would recommend using @polka/compression
since SvelteKit streams responses and the more popular compression
package does not support streaming and may cause errors when used.
Environment variablespermalink
In dev
and preview
, SvelteKit will read environment variables from your .env
file (or .env.local
, or .env.[mode]
, as determined by Vite.)
In production, .env
files are not automatically loaded. To do so, install dotenv
in your project...
npm install dotenv
...and invoke it before running the built app:
node build
node -r dotenv/config build
If you use Node.js v20.6+, you can use the --env-file
flag instead:
node build
node --env-file=.env build
PORT, HOST and SOCKET_PATHpermalink
By default, the server will accept connections on 0.0.0.0
using port 3000. These can be customised with the PORT
and HOST
environment variables:
HOST=127.0.0.1 PORT=4000 node build
Alternatively, the server can be configured to accept connections on a specified socket path. When this is done using the SOCKET_PATH
environment variable, the HOST
and PORT
environment variables will be disregarded.
SOCKET_PATH=/tmp/socket node build
ORIGIN, PROTOCOL_HEADER, HOST_HEADER, and PORT_HEADERpermalink
HTTP doesn't give SvelteKit a reliable way to know the URL that is currently being requested. The simplest way to tell SvelteKit where the app is being served is to set the ORIGIN
environment variable:
ORIGIN=https://my.site node build
# or e.g. for local previewing and testing
ORIGIN=http://localhost:3000 node build
With this, a request for the /stuff
pathname will correctly resolve to https://my.site/stuff
. Alternatively, you can specify headers that tell SvelteKit about the request protocol and host, from which it can construct the origin URL:
PROTOCOL_HEADER=x-forwarded-proto HOST_HEADER=x-forwarded-host node build
x-forwarded-proto
andx-forwarded-host
are de facto standard headers that forward the original protocol and host if you're using a reverse proxy (think load balancers and CDNs). You should only set these variables if your server is behind a trusted reverse proxy; otherwise, it'd be possible for clients to spoof these headers.If you're hosting your proxy on a non-standard port and your reverse proxy supports
x-forwarded-port
, you can also setPORT_HEADER=x-forwarded-port
.
If adapter-node
can't correctly determine the URL of your deployment, you may experience this error when using form actions:
Cross-site POST form submissions are forbidden
ADDRESS_HEADER and XFF_DEPTHpermalink
The RequestEvent object passed to hooks and endpoints includes an event.getClientAddress()
function that returns the client's IP address. By default this is the connecting remoteAddress
. If your server is behind one or more proxies (such as a load balancer), this value will contain the innermost proxy's IP address rather than the client's, so we need to specify an ADDRESS_HEADER
to read the address from:
ADDRESS_HEADER=True-Client-IP node build
Headers can easily be spoofed. As with
PROTOCOL_HEADER
andHOST_HEADER
, you should know what you're doing before setting these.
If the ADDRESS_HEADER
is X-Forwarded-For
, the header value will contain a comma-separated list of IP addresses. The XFF_DEPTH
environment variable should specify how many trusted proxies sit in front of your server. E.g. if there are three trusted proxies, proxy 3 will forward the addresses of the original connection and the first two proxies:
<client address>, <proxy 1 address>, <proxy 2 address>
Some guides will tell you to read the left-most address, but this leaves you vulnerable to spoofing:
<spoofed address>, <client address>, <proxy 1 address>, <proxy 2 address>
We instead read from the right, accounting for the number of trusted proxies. In this case, we would use XFF_DEPTH=3
.
If you need to read the left-most address instead (and don't care about spoofing) — for example, to offer a geolocation service, where it's more important for the IP address to be real than trusted, you can do so by inspecting the
x-forwarded-for
header within your app.
BODY_SIZE_LIMITpermalink
The maximum request body size to accept in bytes including while streaming. The body size can also be specified with a unit suffix for kilobytes (K
), megabytes (M
), or gigabytes (G
). For example, 512K
or 1M
. Defaults to 512kb. You can disable this option with a value of Infinity
(0 in older versions of the adapter) and implement a custom check in handle
if you need something more advanced.
SHUTDOWN_TIMEOUTpermalink
The number of seconds to wait before forcefully closing any remaining connections after receiving a SIGTERM
or SIGINT
signal. Defaults to 30
. Internally the adapter calls closeAllConnections
. See Graceful shutdown for more details.
IDLE_TIMEOUTpermalink
When using systemd socket activation, IDLE_TIMEOUT
specifies the number of seconds after which the app is automatically put to sleep when receiving no requests. If not set, the app runs continuously. See Socket activation for more details.
Optionspermalink
The adapter can be configured with various options:
ts
importCannot find module '@sveltejs/adapter-node' or its corresponding type declarations.2307Cannot find module '@sveltejs/adapter-node' or its corresponding type declarations.adapter from'@sveltejs/adapter-node' ;export default {kit : {adapter :adapter ({// default options are shownout : 'build',precompress : true,envPrefix : ''})}};
outpermalink
The directory to build the server to. It defaults to build
— i.e. node build
would start the server locally after it has been created.
precompresspermalink
Enables precompressing using gzip and brotli for assets and prerendered pages. It defaults to true
.
envPrefixpermalink
If you need to change the name of the environment variables used to configure the deployment (for example, to deconflict with environment variables you don't control), you can specify a prefix:
ts
envPrefix: 'MY_CUSTOM_';
MY_CUSTOM_HOST=127.0.0.1 \
MY_CUSTOM_PORT=4000 \
MY_CUSTOM_ORIGIN=https://my.site \
node build
Graceful shutdownpermalink
By default adapter-node
gracefully shuts down the HTTP server when a SIGTERM
or SIGINT
signal is received. It will:
- reject new requests (
server.close
) - wait for requests that have already been made but not received a response yet to finish and close connections once they become idle (
server.closeIdleConnections
) - and finally, close any remaining connections that are still active after
SHUTDOWN_TIMEOUT
seconds. (server.closeAllConnections
)
If you want to customize this behaviour you can use a custom server.
You can listen to the sveltekit:shutdown
event which is emitted after the HTTP server has closed all connections. Unlike Node's exit
event, the sveltekit:shutdown
event supports asynchronous operations and is always emitted when all connections are closed even if the server has dangling work such as open database connections.
ts
process .on ('sveltekit:shutdown', async (reason ) => {awaitCannot find name 'jobs'.2304Cannot find name 'jobs'.. jobs stop ();awaitCannot find name 'db'.2304Cannot find name 'db'.. db close ();});
The parameter reason
has one of the following values:
SIGINT
- shutdown was triggered by aSIGINT
signalSIGTERM
- shutdown was triggered by aSIGTERM
signalIDLE
- shutdown was triggered byIDLE_TIMEOUT
Socket activationpermalink
Most Linux operating systems today use a modern process manager called systemd to start the server and run and manage services. You can configure your server to allocate a socket and start and scale your app on demand. This is called socket activation. In this case, the OS will pass two environment variables to your app — LISTEN_PID
and LISTEN_FDS
. The adapter will then listen on file descriptor 3 which refers to a systemd socket unit that you will have to create.
You can still use
envPrefix
with systemd socket activation.LISTEN_PID
andLISTEN_FDS
are always read without a prefix.
To take advantage of socket activation follow these steps.
- Run your app as a systemd service. It can either run directly on the host system or inside a container (using Docker or a systemd portable service for example). If you additionally pass an
IDLE_TIMEOUT
environment variable to your app it will gracefully shutdown if there are no requests forIDLE_TIMEOUT
seconds. systemd will automatically start your app again when new requests are coming in.
[Service]
Environment=NODE_ENV=production IDLE_TIMEOUT=60
ExecStart=/usr/bin/node /usr/bin/myapp/build
- Create an accompanying socket unit. The adapter only accepts a single socket.
[Socket]
ListenStream=3000
[Install]
WantedBy=sockets.target
- Make sure systemd has recognised both units by running
sudo systemctl daemon-reload
. Then enable the socket on boot and start it immediately usingsudo systemctl enable --now myapp.socket
. The app will then automatically start once the first request is made tolocalhost:3000
.
Custom serverpermalink
The adapter creates two files in your build directory — index.js
and handler.js
. Running index.js
— e.g. node build
, if you use the default build directory — will start a server on the configured port.
Alternatively, you can import the handler.js
file, which exports a handler suitable for use with Express, Connect or Polka (or even just the built-in http.createServer
) and set up your own server:
ts
import {Cannot find module './build/handler.js' or its corresponding type declarations.2307Cannot find module './build/handler.js' or its corresponding type declarations.handler } from'./build/handler.js' ;importCannot find module 'express' or its corresponding type declarations.2307Cannot find module 'express' or its corresponding type declarations.express from'express' ;constapp =express ();// add a route that lives separately from the SvelteKit appParameter 'req' implicitly has an 'any' type.Parameter 'res' implicitly has an 'any' type.7006app .get ('/healthcheck', (, req ) => { res
7006Parameter 'req' implicitly has an 'any' type.Parameter 'res' implicitly has an 'any' type.res .end ('ok');});// let SvelteKit handle everything else, including serving prerendered pages and static assetsapp .use (handler );app .listen (3000, () => {console .log ('listening on port 3000');});
ts
import {Cannot find module './build/handler.js' or its corresponding type declarations.2307Cannot find module './build/handler.js' or its corresponding type declarations.handler } from'./build/handler.js' ;importCannot find module 'express' or its corresponding type declarations.2307Cannot find module 'express' or its corresponding type declarations.express from'express' ;constapp =express ();// add a route that lives separately from the SvelteKit appParameter 'req' implicitly has an 'any' type.Parameter 'res' implicitly has an 'any' type.7006app .get ('/healthcheck', (, req ) => { res
7006Parameter 'req' implicitly has an 'any' type.Parameter 'res' implicitly has an 'any' type.res .end ('ok');});// let SvelteKit handle everything else, including serving prerendered pages and static assetsapp .use (handler );app .listen (3000, () => {console .log ('listening on port 3000');});