> ## Documentation Index
> Fetch the complete documentation index at: https://algolia.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Sync your URLs with InstantSearch.js

> How to synchronize your URLs with InstantSearch.js.

export const Filter = () => <Tooltip tip="A filter is a condition that limits which records Algolia returns. Filters often use one or more facet-value pairs, such as brand:Apple AND color:red. You can also filter by numeric values, dates, tags, booleans, or geographic constraints." cta="Filtering" href="/doc/guides/managing-results/refine-results/faceting">
    filter
  </Tooltip>;

export const SearchQuery = () => <Tooltip tip="The text users enter into a search box. In the Search API, this corresponds to the query parameter. A search query is often used with filters, facets, and other parameters, but these aren't part of the query text itself.">
    search query
  </Tooltip>;

export const Records = () => <Tooltip tip="A record is a searchable object in an Algolia index. Each record consists of named attributes." cta="Algolia records" href="/doc/guides/sending-and-managing-data/prepare-your-data#algolia-records">
    records
  </Tooltip>;

<Info>
  You are currently reading the documentation for InstantSearch.js v4.
  Read the migration guide to learn [how to upgrade from v3 to v4](/doc/guides/building-search-ui/upgrade-guides/js#upgrade-from-v3-to-v4).
  You can still access the [V3 documentation for this page](https://algolia.com/old-docs/deprecated/instantsearch/js/v3/guides/routing-urls/).
</Info>

Synchronizing your UI with the browser URL is considered good practice.
It lets your users take one of your results pages, copy the URL, and share it.
It also improves the user experience by enabling the use of the back and next browser buttons to keep track of previous searches.

InstantSearch provides the necessary API entries to let you synchronize the state of your search UI (your refined widgets and current <SearchQuery />) with any kind of storage.

This is possible with the [`routing`](/doc/api-reference/widgets/instantsearch/js#param-routing) option. This guide focuses on storing the UI state in the browser URL.

This guide goes through different ways to handle routing with your search UI:

* Enabling routing with no extra configuration
* Manually rewriting URLs to tailor it to your needs
* Crafting SEO-friendly URLs

<Note>
  When you are using routing, you can't use [`initialUiState`](/doc/api-reference/widgets/instantsearch/js#param-initial-ui-state) as the two options override each other. Simple and static use cases can be more straightforward using [`initialUiState`](/doc/api-reference/widgets/instantsearch/js#param-initial-ui-state), but anything dynamic or complex should use `routing`.
</Note>

## Basic URLs

InstantSearch.js lets you enable URL synchronization by setting the [`routing`](/doc/api-reference/widgets/instantsearch/js#param-routing) to `true`.

```js JavaScript icon=code theme={"system"}
const search = instantsearch({
  searchClient,
  indexName: "instant_search",
  routing: true,
});
```

Assume the following search UI state:

* **Query:** "galaxy"

* **Menu:**

  * `categories`: "Cell Phones"

* **Refinement List:**

  * `brand`: "Apple", "Samsung"

* **Page:** 2

This results in the following URL:

```txt theme={"system"}
https://example.org/?instant_search[query]=galaxy&instant_search[menu][categories]=All Unlocked Cell Phones&instant_search[refinementList][brand][0]=Apple&instant_search[refinementList][brand][0]=Samsung&instant_search[page]=2
```

This URL is accurate, and can be translated back to a search UI state

## Manually rewrite URLs

<Note>
  All examples in this guide assume you've included InstantSearch.js in your web page from a CDN.
  If you use a package manager instead, adjust how you [import InstantSearch.js and its widgets](/doc/guides/building-search-ui/installation/js).
</Note>

The default URLs that InstantSearch generates are comprehensive,
but if you have many widgets, this can also generate noise.
You may want to decide what goes in the URL and what doesn't,
or even rename the query parameters to something that makes more sense to you.

Setting [`routing`](/doc/api-reference/widgets/instantsearch/js#param-routing) to `true` is syntactic sugar for the following code:

```js JavaScript icon=code theme={"system"}
const search = instantsearch({
  searchClient,
  indexName: "instant_search",
  routing: {
    router: instantsearch.routers.history(),
    stateMapping: instantsearch.stateMappings.simple(),
  },
});
```

The `stateMapping` option defines how to go from InstantSearch's internal state to a URL, and vice versa.
You can use it to rename query parameters and choose what to include in the URL.

```js JavaScript icon=code theme={"system"}
const search = instantsearch({
  searchClient,
  indexName: "instant_search",
  routing: {
    stateMapping: {
      stateToRoute(uiState) {
        // ...
      },
      routeToState(routeState) {
        // ...
      },
    },
  },
});
```

InstantSearch manages [`uiState`](/doc/api-reference/widgets/ui-state/js).

The state contains information about the user's search, including the query,
the <Filter /> selection,
the page being viewed,
and the widget hierarchy.
`uiState` only stores modified widget values, not defaults.

To persist this state in the URL,
InstantSearch converts the `uiState` into an object called `routeState`:
this `routeState` then becomes a URL.
Conversely, when InstantSearch reads the URL and applies it to the search,
it converts `routeState` into `uiState`.
This logic lives in two functions:

* `stateToRoute`: converts `uiState` to `routeState`.
* `routeToState`: converts `routeState` to `uiState`.

Assume the following search UI state:

* **Query:** "galaxy"

* **Menu:**

  * `categories`: "Cell Phones"

* **Refinement List:**

  * `brand`: "Apple" and "Samsung"

* **Page:** 2

This translates into the following `uiState`:

```json JSON icon="braces" theme={"system"}
{
  "indexName": {
    "query": "galaxy",
    "menu": {
      "categories": "Cell Phones"
    },
    "refinementList": {
      "brand": ["Apple", "Samsung"]
    },
    "page": 2
  }
}
```

Implement `stateToRoute` to flatten this object into a URL, and `routeToState` to restore the URL into a UI state:

```js JavaScript icon=code theme={"system"}
const indexName = "instant_search";

const search = instantsearch({
  searchClient,
  indexName,
  routing: {
    stateMapping: {
      stateToRoute(uiState) {
        const indexUiState = uiState[indexName];
        return {
          q: indexUiState.query,
          categories: indexUiState.menu && indexUiState.menu.categories,
          brand:
            indexUiState.refinementList && indexUiState.refinementList.brand,
          page: indexUiState.page,
        };
      },
      routeToState(routeState) {
        return {
          [indexName]: {
            query: routeState.q,
            menu: {
              categories: routeState.categories,
            },
            refinementList: {
              brand: routeState.brand,
            },
            page: routeState.page,
          },
        };
      },
    },
  },
});
```

## SEO-friendly URLs

URLs are more than [query parameters](https://en.wikipedia.org/wiki/Query_string).
Another important part is the [path](https://developer.mozilla.org/en-US/docs/Web/API/URL/pathname).
Manipulating the URL path is a common ecommerce pattern that lets you better reference your result pages.

```txt theme={"system"}
https://example.org/search/Cell+Phones/?query=galaxy&page=2&brands=Apple&brands=Samsung
```

### Example implementation

Here's an example that stores the brand in the path, and the query and page as query parameters.

```js JavaScript icon=code theme={"system"}
// Returns a slug from the category name.
// Spaces are replaced by "+" to make
// the URL easier to read and other
// characters are encoded.
function getCategorySlug(name) {
  return name.split(" ").map(encodeURIComponent).join("+");
}

// Returns a name from the category slug.
// The "+" are replaced by spaces and other
// characters are decoded.
function getCategoryName(slug) {
  return slug.split("+").map(decodeURIComponent).join(" ");
}

const search = instantsearch({
  searchClient,
  indexName: "instant_search",
  routing: {
    router: instantsearch.routers.history({
      windowTitle({ category, query }) {
        const queryTitle = query ? `Results for "${query}"` : "Search";

        if (category) {
          return `${category} – ${queryTitle}`;
        }

        return queryTitle;
      },

      createURL({ qsModule, routeState, location }) {
        const urlParts = location.href.match(/^(.*?)\/search/);
        const baseUrl = `${urlParts ? urlParts[1] : ""}/`;

        const categoryPath = routeState.category
          ? `${getCategorySlug(routeState.category)}/`
          : "";
        const queryParameters = {};

        if (routeState.query) {
          queryParameters.query = encodeURIComponent(routeState.query);
        }
        if (routeState.page !== 1) {
          queryParameters.page = routeState.page;
        }
        if (routeState.brands) {
          queryParameters.brands = routeState.brands.map(encodeURIComponent);
        }

        const queryString = qsModule.stringify(queryParameters, {
          addQueryPrefix: true,
          arrayFormat: "repeat",
        });

        return `${baseUrl}search/${categoryPath}${queryString}`;
      },

      parseURL({ qsModule, location }) {
        const pathnameMatches = location.pathname.match(/search\/(.*?)\/?$/);
        const category = getCategoryName(
          (pathnameMatches && pathnameMatches[1]) || "",
        );
        const {
          query = "",
          page,
          brands = [],
        } = qsModule.parse(location.search.slice(1));
        // `qs` does not return an array when there's a single value.
        const allBrands = Array.isArray(brands)
          ? brands
          : [brands].filter(Boolean);

        return {
          query: decodeURIComponent(query),
          page,
          brands: allBrands.map(decodeURIComponent),
          category,
        };
      },
    }),

    stateMapping: {
      stateToRoute(uiState) {
        const indexUiState = uiState["instant_search"] || {};

        return {
          query: indexUiState.query,
          page: indexUiState.page,
          brands:
            indexUiState.refinementList && indexUiState.refinementList.brand,
          category: indexUiState.menu && indexUiState.menu.categories,
        };
      },

      routeToState(routeState) {
        return {
          instant_search: {
            query: routeState.query,
            page: routeState.page,
            menu: {
              categories: routeState.category,
            },
            refinementList: {
              brand: routeState.brands,
            },
          },
        };
      },
    },
  },
});
```

You're now using the [`instantsearch.routers.history`](/doc/api-reference/widgets/history-router/js) to explicitly set options on the default router mechanism. The `router` and `stateMapping` options are used to map `uiState` to `routeState`, and vice versa.

Using the `routing` option as an object, you can configure:

* `windowTitle`: a method to map the `routeState` object returned from `stateToRoute` to the window title.

* `createURL`: a method called every time you need to create a URL. When:

  * You want to synchronize the `routeState` to the browser URL
  * You want to render `a` tags in the `menu` widget
  * You call `createURL` in one of your connectors' rendering methods.

* `parseURL`: a method called every time users load or reload the page, or click the browser's back or next buttons.

### Make URLs more discoverable

In real-life applications, you might want to make some categories more accessible, with a URL that's easier to read and to remember.

Given your dataset, you can make some categories more discoverable:

* "Cameras and camcorders" → `/Cameras`
* "Car electronics and GPS" → `/Cars`

In this example, on arrival at `https://example.org/search/Cameras`, it pre-selects the "Cameras and camcorders" filter.

You can achieve this with a dictionary.

```js JavaScript icon=code theme={"system"}
// Add the dictionaries to convert the names and the slugs
const encodedCategories = {
  Cameras: "Cameras and camcorders",
  Cars: "Car electronics and GPS",
  Phones: "Phones",
  TV: "TV and home theater",
};

const decodedCategories = Object.keys(encodedCategories).reduce((acc, key) => {
  const newKey = encodedCategories[key];
  const newValue = key;

  return {
    ...acc,
    [newKey]: newValue,
  };
}, {});

// Update the getters to use the encoded/decoded values
function getCategorySlug(name) {
  const encodedName = decodedCategories[name] || name;

  return encodedName.split(" ").map(encodeURIComponent).join("+");
}

function getCategoryName(slug) {
  const decodedSlug = encodedCategories[slug] || slug;

  return decodedSlug.split("+").map(decodeURIComponent).join(" ");
}
```

You can build these dictionaries from your Algolia <Records />.

With such a solution, you have full control over what categories are discoverable from the URL.

### About SEO

For your search results to be part of a public search engine's results, you must be selective.
Trying to index too many search results pages could be considered spam.

To do that, create a [`robots.txt`](http://www.robotstxt.org/) and host it at `https://example.org/robots.txt`.

Here's an example based on the URL scheme you created.

```txt robots.txt theme={"system"}
User-agent: *
Allow: /search/Audio/
Allow: /search/Phones/
Disallow: /search/
Allow: *
```

For more information, see:

* [`routing`](/doc/api-reference/widgets/instantsearch/js#param-routing).
* [Basic routing demo](https://codesandbox.io/s/github/algolia/doc-code-samples/tree/master/instantsearch.js/routing-basic)
* [SEO-friendly routing demo](https://codesandbox.io/s/github/algolia/doc-code-samples/tree/master/instantsearch.js/routing-seo-friendly)

### Remove unrelated URL parameters from the URL

**Applies to InstantSearch.js v3 and later.**

If you enable InstantSearch routing, only the parameters coming from widgets are included in the URL.
To keep other parameters unrelated to InstantSearch, add them when implementing `createURL`.

For example, to keep all URL parameters that start with `utm_`, use the following code:

```js JavaScript icon=code theme={"system"}
history({
  // ... other options
  parseURL({ qsModule, location }) {
    return qsModule.parse(location.search.slice(1));
  },
  createURL({ qsModule, location, routeState }) {
    const { origin, pathname, hash } = location;

    const queriesFromUrl = qsModule.parse(location.search.slice(1));

    // Get all parameters from the URL that are not in the InstantSearch state and that start with "utm_"
    const utmQueries = Object.fromEntries(
      Object.entries(queriesFromUrl).filter(
        ([key]) =>
          !Object.keys(routeState).includes(key) &&
          // Add here a condition to keep the parameters you want, for example starting with "utm_"
          key.startsWith("utm_"),
      ),
    );

    // Create query string with InstantSearch state and other parameters
    const queryString = qsModule.stringify(
      {
        ...routeState,
        ...utmQueries,
      },
      {
        addQueryPrefix: true,
        arrayFormat: "repeat",
      },
    );

    return `${origin}${pathname}${queryString}${hash}`;
  },
});
```

## Group facet values

**Applies to InstantSearch.js v1 and later.**

If you want to group, for example, "turquoise", "ocean" and "sky" under "blue", the recommended solution is to group them at indexing time.
You can either add the group name as a separate attribute to globally filter on,
or add both values in an array to make both the group and the individual value show up in the list.

For example, with the following dataset:

```json JSON icon=braces theme={"system"}
[
  {
    "objectID": "1",
    "color": "turquoise"
  },
  {
    "objectID": "2",
    "color": "ocean"
  },
  {
    "objectID": "3",
    "color": "sky"
  }
]
```

You could create an additional attribute and use it for faceting:

```json JSON icon=braces theme={"system"}
[
  {
    "objectID": "1",
    "color": "turquoise",
    "colorGroup": "blue"
  },
  {
    "objectID": "2",
    "color": "ocean",
    "colorGroup": "blue"
  },
  {
    "objectID": "3",
    "color": "sky",
    "colorGroup": "blue"
  }
]
```

Or you could list the individual colors and their groups so you can use them both for faceting:

```json JSON icon=braces theme={"system"}
[
  {
    "objectID": "1",
    "color": ["turquoise", "blue"]
  },
  {
    "objectID": "2",
    "color": ["ocean", "blue"]
  },
  {
    "objectID": "3",
    "color": ["sky", "blue"]
  }
]
```