# Can I use Atomico in browsers without ESM support?

Yes, but Atomico doesn't only depend on ESM, it also depends on the following api's that you will have to cover with Polyfill or some bundle tool.

1. ESM modules: [documentation ](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules)- [caniuse](https://caniuse.com/es6-module)
2. CustomElements: [documentation](https://developer.mozilla.org/en-US/docs/Web/API/Window/customElements) - [caniuse](https://caniuse.com/mdn-api_window_customelements)
3. ShadowRoot: [documentation](https://developer.mozilla.org/en-US/docs/Web/API/ShadowRoot) - [caniuse](https://caniuse.com/mdn-api_shadowroot)
4. Map: [documentation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) - [caniuse](https://caniuse.com/mdn-html_elements_map)
5. Symbol and Symbol.for: [documentation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/for) - [caniuse](https://caniuse.com/mdn-api_element_prepend)
6. append and prepend: [documentation ](https://developer.mozilla.org/en-US/docs/Web/API/Element/prepend)- [caniuse](https://caniuse.com/mdn-api_element_prepend)
7. Declarative Shadow DOM: **Only for using SSR with webcomponents that use shadowDOM**. [documentation](https://developer.chrome.com/es/articles/declarative-shadow-dom/)

Let's understand that today Atomico covers 94% of existing browsers without the need for polyfills or packers, the 6% not covered are usually browsers like ie11 or others.

If you depend on the uncovered segment of browsers you can use the following tools to support the apis necessary for Atomico to work.

[polyfill-fastly.io](https://polyfill-fastly.io/v3/polyfill.min.js?features=Element.prototype.append%2CSymbol%2CElement.prototype.prepend%2CMap) to associate Map, Symbol, append and prepend.

<https://github.com/Rich-Harris/shimport> to associate esm.

<https://github.com/ungap/custom-elements> to associate customElements apis.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://atomico.gitbook.io/doc/guides/frequent-questions/page.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.