Error Handling
Learn how to handle errors in Bun's development server
Bun.serve() runs in development mode by default. It is turned off when NODE_ENV=production is set or when you pass development: false.
Bun.serve({
development: false,
fetch(req) {
throw new Error("woops!");
},
});In development mode, when a request handler throws and no error handler returns a response, Bun responds with a built-in error page that includes the error message, stack trace, source code around each frame, and file paths. This is meant for debugging locally.
The development error page sends source code and file paths to whoever made the request. Set NODE_ENV=production (or
development: false) when deploying so uncaught errors return a plain 500 instead. The --production flag does not
turn it off: bun build and bun install have that flag, and bun run ignores it.
error callback
To handle server-side errors, implement an error handler. Return a Response to serve to the client when an error occurs. In development mode, this response replaces Bun’s default error page.
Bun.serve({
fetch(req) {
throw new Error("woops!");
},
error(error) {
return new Response(`<pre>${error}\n${error.stack}</pre>`, {
headers: {
"Content-Type": "text/html",
},
});
},
});