Guides / Building Search UI

What is InstantSearch.js?

InstantSearch.js is an open source UI library for Vanilla JS that lets you quickly build a search interface in your frontend application.

InstantSearch’s goal is to help you implement awesome search experiences as smoothly as possible by providing a complete search ecosystem. InstantSearch tackles an important part of this vast goal by providing frontend widgets that you can assemble into unique search interfaces.

The InstantSearch family is composed of multiple InstantSearch flavors:

A progressive customization API

InstantSearch.js, like any InstantSearch flavor, should be used progressively. It provides three layers of usage that get progressively more powerful, with each level giving you more control.

  1. At first you’ll be using predefined widgets, which you can configure and place on your UI, but they don’t give you access to the DOM output.
  2. Eventually you’ll want to re-define the render output of a widget. You can do this by extending widgets. This is a hybrid solution, where you start with the built-in widgets, and then you can take over control of the render output.
  3. Finally, if you want to implement a completely new widget that doesn’t exist, create custom widgets, giving you full control over the UI component as well as its render output.

Using widgets

Widgets in InstantSearch.js are building blocks that have a predefined behavior and render output.

Widgets usually have options to alter their behavior. Pass options to widgets with attributes.

For example, here’s how to use the refinementList widget:

  container: document.querySelector('#brand'),
  attribute: 'brand',

Here, you’re adding the refinementList widget and asking it to show a list of brands, thus allowing your users to “refine” their search by brand.

InstantSearch.js bundles the widgets that are most often used in search experiences.

But before you can use the refinementList widget, you need to create the InstantSearch instance.

The InstantSearch instance

This instance is responsible for the communication between your application and Algolia. This instance is where you add all the widgets. Here’s how:

const searchClient = algoliasearch(

const search = instantsearch({
  indexName: 'instant_search',

    container: document.querySelector('#brand'),
    attribute: 'brand',

Once you have added all the wanted widgets to the instance, you have to call the start method to actually start the search:


You can learn more about this in the InstantSearch.js API reference and in the getting started.

Extending widgets

Widgets with predefined behavior, which output a very specific set of DOM elements, aren’t always sufficient to answer your needs. You might want, for example, to completely change the rendering of the menu widget so that it renders as a select element instead of a list of links.

This can’t be answered by adding more options. What if you want to render a menu widget as a keyboard controlled slideshow of images? No simple option will ever fulfill and scale those needs.

That’s why InstantSearch.js provides a second API layer: extending widgets. The actual API feature behind this use case is called connectors and is common to all InstantSearch flavors.

By extending widgets, you are able to completely redefine a widget’s behavior and its DOM output.

To know more, and to use this API feature, read the extending widgets guide.

Creating custom widgets

Finally, when none of the previous solutions work for you and you want to create a completely new widget from scratch, InstantSearch provides a third layer of API for this: creating custom widgets. This requires two APIs: the first one lets you create a new connector, and the second one lets you create a new widget. Both solutions give you full control of the render and behavior.

When building a new widget, you must be prepared to dive deep into the Algolia semantics to achieve what you want.

To know more and to use this API feature, read the creating custom widgets guide.

CSS theme

Since every widget in InstantSearch.js has a predefined DOM output, you can load the provided default CSS theme in your application.

Here’s a preview of the theme:

Theme preview

Within its predefined DOM output, every widget exposes a list of CSS classes that you can use to update the styling of the rendering.

For more information, see Style your widgets.

Need help?

InstantSearch.js is worked on full-time by Algolia’s JavaScript team.

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