TOML - Bun

In Bun, TOML is a first-class citizen alongside JSON, JSON5, and YAML. You can:

Parse TOML strings with Bun.TOML.parse
import & require TOML files as modules at runtime (including hot reloading & watch mode support)
import & require TOML files in frontend apps with Bun’s bundler

Runtime API

`Bun.TOML.parse()`

Parse a TOML string into a JavaScript object.

import { TOML } from "bun";
const text = `
name = "my-app"
version = "1.0.0"
debug = true

[database]
host = "localhost"
port = 5432

[features]
tags = ["web", "api"]
`;

const data = TOML.parse(text);
console.log(data);
// {
//   name: "my-app",
//   version: "1.0.0",
//   debug: true,
//   database: { host: "localhost", port: 5432 },
//   features: { tags: ["web", "api"] }
// }

Supported TOML Features

Bun’s TOML parser supports the TOML v1.0 specification, including:

Strings: basic ("...") and literal ('...'), including multi-line
Integers: decimal, hex (0x), octal (0o), and binary (0b)
Floats
Booleans: true and false
Arrays: including mixed types and nested arrays
Tables: standard ([table]) and inline ({ key = "value" })
Array of tables: [[array]]
Dotted keys: a.b.c = "value"
Comments: using #

const data = Bun.TOML.parse(`
# Application config
title = "My App"

[owner]
name = "John Doe"

[database]
enabled = true
ports = [8000, 8001, 8002]
connection_max = 5000

[servers.alpha]
ip = "10.0.0.1"
role = "frontend"

[servers.beta]
ip = "10.0.0.2"
role = "backend"
`);

Error Handling

Bun.TOML.parse() throws if the TOML is invalid:

try {
  Bun.TOML.parse("invalid = = =");
} catch (error) {
  console.error("Failed to parse TOML:", error.message);
}

Module Import

ES Modules

Import TOML files directly as ES modules. Bun parses the TOML and exposes it as both default and named exports:

config.toml

[database]
host = "localhost"
port = 5432
name = "myapp"

[redis]
host = "localhost"
port = 6379

[features]
auth = true
rateLimit = true
analytics = false

Default Import

app.ts

import config from "./config.toml";

console.log(config.database.host); // "localhost"
console.log(config.redis.port); // 6379

Named Imports

You can destructure top-level TOML tables as named imports:

app.ts

import { database, redis, features } from "./config.toml";

console.log(database.host); // "localhost"
console.log(redis.port); // 6379
console.log(features.auth); // true

Or combine both:

app.ts

import config, { database, features } from "./config.toml";

// Use the full config object
console.log(config);

// Or use specific parts
if (features.rateLimit) {
  setupRateLimiting(database);
}

Import Attributes

Use an import attribute to load any file as TOML:

app.ts

import myConfig from "./my.config" with { type: "toml" };

CommonJS

You can also require TOML files in CommonJS:

app.ts

const config = require("./config.toml");
console.log(config.database.name); // "myapp"

// Destructuring also works
const { database, redis } = require("./config.toml");
console.log(database.port); // 5432

Hot Reloading with TOML

When you run your application with bun --hot, Bun detects changes to TOML files and reloads them without restarting:

config.toml

[server]
port = 3000
host = "localhost"

[features]
debug = true
verbose = false

server.ts

import { server, features } from "./config.toml";

console.log(`Starting server on ${server.host}:${server.port}`);

Bun.serve({
  port: server.port,
  hostname: server.host,
  fetch(req) {
    if (features.verbose) {
      console.log(`${req.method} ${req.url}`);
    }
    return new Response("Hello World");
  },
});

Run with hot reloading:

terminal

bun --hot server.ts

Bundler Integration

When you bundle with Bun, the bundler parses imported TOML at build time and includes it as a JavaScript module:

terminal

bun build app.ts --outdir=dist

This means:

Zero runtime TOML parsing overhead in production
Smaller bundle sizes
Tree shaking of unused properties (named imports)

Dynamic Imports

You can also dynamically import TOML files:

const config = await import("./config.toml");

​Runtime API

​Bun.TOML.parse()

​Supported TOML Features

​Error Handling

​Module Import

​ES Modules

​Default Import

​Named Imports

​Import Attributes

​CommonJS

​Hot Reloading with TOML

​Bundler Integration

​Dynamic Imports

Runtime API

`Bun.TOML.parse()`

Supported TOML Features

Error Handling

Module Import

ES Modules

Default Import

Named Imports

Import Attributes

CommonJS

Hot Reloading with TOML

Bundler Integration

Dynamic Imports