---
title: "JSX"
description: "Built-in JSX and TSX support in Bun with configurable transpilation options"
---
Bun supports `.jsx` and `.tsx` files. Bun's internal transpiler converts JSX syntax into vanilla JavaScript before execution.
```ts react.tsx icon="/icons/typescript.svg"
function Component(props: {message: string}) {
return (
{props.message}
);
}
console.log();
```
## Configuration
Bun reads your `tsconfig.json` or `jsconfig.json` to determine how to perform the JSX transform internally. If you'd rather not use either, you can set the same options in [`bunfig.toml`](/runtime/bunfig).
Bun respects the following compiler options.
### [`jsx`](https://www.typescriptlang.org/tsconfig#jsx)
How Bun transforms JSX constructs into vanilla JavaScript internally. The following table lists the possible values of `jsx`, along with how each transpiles this JSX component:
```tsx
Hello
```
| Compiler options | Transpiled output |
| --------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `json
{
"jsx": "react"
}
` | `tsx
React.createElement(Box, { width: 5 }, "Hello");
` |
| `json
{
"jsx": "react-jsx"
}
` | `tsx
import { jsx } from "react/jsx-runtime";
jsx(Box, { width: 5, children: "Hello" });
` |
| `json
{
"jsx": "react-jsxdev"
}
` | `tsx
import { jsxDEV } from "react/jsx-dev-runtime";
jsxDEV(
Box,
{ width: 5, children: "Hello" },
undefined,
false,
undefined,
this,
);
`
The `jsxDEV` variable name is a React convention. The `DEV` suffix marks code intended for development. The development version of React is slower and includes additional validity checks & debugging tools. |
| `json
{
"jsx": "preserve"
}
` | `tsx
// JSX is not transpiled
// "preserve" is not supported by Bun currently
Hello
` |
### [`jsxFactory`](https://www.typescriptlang.org/tsconfig#jsxFactory)
Only applicable when `jsx` is `react`.
The function name used to represent JSX constructs. Default value is `"React.createElement"`. Set this for libraries like [Preact](https://preactjs.com/) that use a different function name (`"h"`).
| Compiler options | Transpiled output |
| --------------------------------------------------------------------- | --------------------------------------------- |
| `json
{
"jsx": "react",
"jsxFactory": "h"
}
` | `tsx
h(Box, { width: 5 }, "Hello");
` |
### [`jsxFragmentFactory`](https://www.typescriptlang.org/tsconfig#jsxFragmentFactory)
Only applicable when `jsx` is `react`.
The function name used to represent [JSX fragments](https://react.dev/reference/react/Fragment) such as `<>Hello`. Default value is `"React.Fragment"`.
| Compiler options | Transpiled output |
| ------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------ |
| `json
{
"jsx": "react",
"jsxFactory": "myjsx",
"jsxFragmentFactory": "MyFragment"
}
` | `tsx
// input
<>Hello;
// output
myjsx(MyFragment, null, "Hello");
` |
### [`jsxImportSource`](https://www.typescriptlang.org/tsconfig#jsxImportSource)
Only applicable when `jsx` is `react-jsx` or `react-jsxdev`.
The module the component factory function (such as `createElement`, `jsx`, or `jsxDEV`) is imported from. Default value is `"react"`. You typically need this when using a component library like Preact.
| Compiler options | Transpiled output |
| ---------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `jsonc
{
"jsx": "react-jsx",
// jsxImportSource is not defined
// default to "react"
}
` | `tsx
import { jsx } from "react/jsx-runtime";
jsx(Box, { width: 5, children: "Hello" });
` |
| `jsonc
{
"jsx": "react-jsx",
"jsxImportSource": "preact",
}
` | `tsx
import { jsx } from "preact/jsx-runtime";
jsx(Box, { width: 5, children: "Hello" });
` |
| `jsonc
{
"jsx": "react-jsxdev",
"jsxImportSource": "preact",
}
` | `tsx
// /jsx-dev-runtime is automatically appended
import { jsxDEV } from "preact/jsx-dev-runtime";
jsxDEV(
Box,
{ width: 5, children: "Hello" },
undefined,
false,
undefined,
this,
);
` |
### JSX pragma
You can set any of these values per file with a _pragma_, a comment that sets a compiler option in a particular file.
| Pragma | Equivalent config |
| ---------------------------------------- | ------------------------------------------------------------------ |
| `ts
// @jsx h
` | `jsonc
{
"jsxFactory": "h",
}
` |
| `ts
// @jsxFrag MyFragment
` | `jsonc
{
"jsxFragmentFactory": "MyFragment",
}
` |
| `ts
// @jsxImportSource preact
` | `jsonc
{
"jsxImportSource": "preact",
}
` |
## Logging
Bun implements special logging for JSX to help with debugging. Given the following file:
```tsx index.tsx icon="/icons/typescript.svg"
import { Stack, UserCard } from "./components";
console.log(
,
);
```
Bun pretty-prints the component tree:
## Prop punning
The Bun runtime also supports "prop punning" for JSX: a shorthand for assigning a variable to a prop with the same name.
```tsx react.tsx icon="/icons/typescript.svg"
function Div(props: {className: string;}) {
const {className} = props;
// without punning
return ;
// with punning
return ;
}
```