Use a different build tool

Oct 13, 2025 by pynkocean.com 109 views

Can't Use Custom Hosts Anymore with BuildContext.serve: A Painful Change in esbuild 0.25

In the latest version of esbuild, 0.25, a significant change has been made that affects how developers can serve their applications locally. Specifically, the ability to use custom hosts with BuildContext.serve has been removed. This change has caused frustration among developers who relied on this feature for local development, especially when working with self-signed certificates. In this article, we will explore the impact of this change and discuss possible solutions.

Prior to esbuild 0.25, developers could use custom hosts with BuildContext.serve to serve their applications locally. This was particularly useful when working with self-signed certificates, as it allowed developers to test their applications on custom domains without the need for a proxy server. The host argument in BuildContext.serve was used to specify the custom host name, and developers could then edit their /etc/hosts file to map the custom domain to 127.0.0.1.

With the release of esbuild 0.25, the ability to use custom hosts with BuildContext.serve has been removed. When attempting to serve an application with a custom host name, developers are now met with an error message stating that the host is not allowed. This change has caused significant inconvenience for developers who relied on this feature for local development.

To illustrate the issue, let's take a look at an example code snippet that demonstrates how to serve an application with a custom host name using BuildContext.serve in esbuild 0.24.2:

const serveResult = await esbuildContext.serve({
  host: process.env.HOST ?? 'localhost',
  port: Number(process.env.PORT ?? 3000),
  certfile: process.env.CERTFILE,
  keyfile: process.env.KEYFILE,
  servedir: 'build',
  fallback: 'build/index.html'
});

In this example, the host argument is used to specify the custom host name, which is then mapped to 127.0.0.1 in the /etc/hosts file.

When attempting to serve an application with a custom host name using esbuild 0.25, developers are met with the following error message:

Error: host not allowed

This error message indicates that the custom host name is not allowed, and the application cannot be served.

While the removal of custom hosts with BuildContext.serve in esbuild 0.25 is a significant change, there are possible solutions that developers can use to work around this issue. Here are a few possible solutions:

Use a proxy server: One possible solution is to use a proxy server to serve the application on a custom domain. This can be done using tools like NGINX or Apache.
Use a different build tool: Another possible solution is to use a different build tool that supports custom hosts, such as Webpack or Rollup.
Downgrade to esbuild 0.24.2: For developers who rely heavily on custom hosts with BuildContext.serve, downgrading to esbuild 0.24.2 may be the best solution.

The removal of custom hosts with BuildContext.serve in esbuild 0.25 has caused significant inconvenience for developers who relied on this feature for local development. While there are possible solutions that developers can use to work around this issue, the removal of this feature is a significant change that affects the way developers can serve their applications locally. In this article, we have explored the impact of this change and discussed possible solutions.
Can't Use Custom Hosts Anymore with BuildContext.serve: A Painful Change in esbuild 0.25

Q&A: Frequently Asked Questions about the Removal of Custom Hosts with BuildContext.serve

A: The reason behind the removal of custom hosts with BuildContext.serve in esbuild 0.25 is not explicitly stated by the esbuild team. However, it is likely due to security concerns related to custom hosts. Custom hosts can be used to serve malicious content, and the esbuild team may have decided to remove this feature to improve the security of the build tool.

A: Yes, you can still use custom hosts with BuildContext.serve in esbuild 0.24.2. This version of esbuild still supports custom hosts, and you can use it as a temporary solution until the issue is resolved.

A: Some possible solutions to the removal of custom hosts with BuildContext.serve include:

Using a proxy server: You can use a proxy server like NGINX or Apache to serve your application on a custom domain.
Using a different build tool: You can use a different build tool like Webpack or Rollup that supports custom hosts.
Downgrading to esbuild 0.24.2: If you rely heavily on custom hosts with BuildContext.serve, downgrading to esbuild 0.24.2 may be the best solution.

A: Configuring a proxy server to serve your application on a custom domain involves several steps:

Install a proxy server: You can install a proxy server like NGINX or Apache on your local machine.
Configure the proxy server: You need to configure the proxy server to serve your application on a custom domain. This involves creating a configuration file and specifying the custom domain and the path to your application.
Test the proxy server: Once you have configured the proxy server, you need to test it to ensure that it is working correctly.

A: Yes, you can use a self-signed certificate with a proxy server. However, you need to configure the proxy server to trust the self-signed certificate. This involves creating a certificate file and specifying the path to the certificate file in the proxy server configuration.

A: Configuring a different build tool to support custom hosts involves several steps:

Choose a different build tool: You need to choose a different build tool like Webpack or Rollup that supports custom hosts.
Configure the build tool: You need to configure the build tool to serve your application on a custom domain. This involves creating a configuration file and specifying the custom domain and the path to your application.
Test the build tool: Once you have configured the build tool, you need to test it to ensure that it is working correctly.

A: No, you should not use a custom host with BuildContext.serve in a production environment. Custom hosts are typically used for local development and testing, and they are not suitable for production environments. In a production environment, you should use a secure and reliable hosting solution that supports HTTPS and other security features.