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Trevor I. Lasn

Building tools for developers. Currently building skillcraft.ai and blamesteve.lol

JavaScript Import Attributes (ES2025)

Understanding the new import attributes syntax and why we can't rely on file extensions alone

JavaScript is getting a new feature that makes module imports more explicit and secure. Import Attributes add a way to pass metadata about any module we’re importing - whether it’s JSON, JavaScript, or other module types.

The Core Problem

On the web, file extensions don’t reliably indicate content. A server might return JavaScript when you’re expecting JSON:


The Solution: Import Attributes

Import Attributes create a contract between your code and the runtime. You explicitly declare what type of module you expect:

The syntax works consistently across different module contexts:


Why Import Attributes?

The core problem is security. On the web, file extensions don’t reliably indicate content. A URL ending in .json might actually serve JavaScript:

Import Attributes make our module system more explicit and secure. JSON modules can’t execute code - they’re pure data. When you mark a module with type: "json", you’re guaranteed to get either JSON data or an error, never executable code.

The most immediate impact is on JSON imports, where security is crucial:

This feature creates a foundation for safely handling different module types in JavaScript. When it lands in 2025, we’ll have a standard way to declare our expectations about modules across all JavaScript environments.

Think of it as adding type safety to your module imports - not for the data inside the modules, but for the modules themselves.

Sources


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This article was originally published on https://www.trevorlasn.com/blog/import-attributes-in-javascript. It was written by a human and polished using grammar tools for clarity.