Concepts / Building Search UI / What is InstantSearch.js?
May. 16, 2019

What Is InstantSearch.js?

You are currently reading the documentation for InstantSearch.js V3. Read our migration guide to learn how to upgrade from V2 to V3. You can still find the V2 documentation here.

InstantSearch is a family of open-source, production-ready UI libraries that eases the usage and installation of the Algolia search engine.

It provides high-level UI widgets that interact with Algolia’s API, to easily build instant-search applications, where you focus on building your UI instead of needing to understand every detail of the Algolia search engine right away.

You are currently reading the InstantSearch.js documentation. It is dedicated to Vanilla JS.

The InstantSearch family is composed of multiple InstantSearch flavors, no matter your front-end stack we got you covered:

A progressive customization API

InstantSearch.js, like any InstantSearch flavors, is designed to be used progressively; that is, 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 pre-defined widgets, which you can configure and place on your UI, but they do not 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 our widgets, and then you can take over control of the render output.
  3. Finally, if you want to implement a completely new widget that does not exist - thus giving you full control over the the UI component as well as its render output - you’ll want to create custom widgets.

Using widgets

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

Similar with all InstantSearch flavors, we call them widgets for uniformity, but they may use another term for widgets.

Widgets usually have options to alter their behavior a bit; options can be passed to widgets via attributes.

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

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

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

There are many widgets bundled with InstantSearch.js; we try to bundle the ones that we think are the most used in all search UIs. Have a look at the widget showcase.

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 pre-defined behavior, which output a very specific set of DOM, are not 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 cannot 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 that we call 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, then we provide a third layer of API to do that: creating custom widgets. There are two APIs that allow you to do this: the fist one let’s your create a new connector and the second one let’s you directly create a new widget. Both of this solution will let you have the full control of the render but also on the behavior. This is a use case where you have to be prepared to learn a lot of the Algolia semantics in order to achieve what you want. But in some situations this might be the only way out.

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, we also provide a default CSS theme that you can load 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 on how to style widgets, read the styling and CSS classes guide.

Need help?

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

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