With these APIs, you can upload your data to create new layers.

Elements enable you to annotate maps with custom shapes, text, and markers.

With these APIs, you can create, update, and delete map elements.

With these APIs, you can publish your layers to your workspace library.

Comments bring conversations to mapping.

With these APIs, you can export, resolve, and delete map comments and collaboration threads.

Users represent the people in your workspace.

With these APIs, you can retrieve user profile information.

Projects help you organize maps and manage team permissions.

With these APIs, you can manage the projects in your workspace.

Layers enable you to visualize, style and interact with your spatial data.

With these APIs, you can upload data, manage layer styling, publish and refresh live data layers.

Maps are the centerpiece of Felt.

With these APIs, you can create, retrieve, update, delete, move, and duplicate maps programmatically.

Embed tokens enable safely sharing your private maps.

With these APIs, you can generate secure tokens for embedding maps.

With these APIs, you can export data to CSV, GeoJSON, and other formats.

Felt’s Developer Tools

There are a variety of ways to interact with Felt’s modern GIS platform outside of the user interface. They can be grouped into two buckets: tools for programmatically creating and modifying maps, and tools for building custom experiences for map viewers. These tools can be used to solve distinct challenges and also be used in tandem with one another.

Sources connect your databases to Felt.

With these APIs, you can configure data source connections, credentials, and sync settings to create live maps.

The Felt SDK has a number of methods for interacting with maps, depending on how you set up your HTML.

All Felt maps are embedded in iframes, and the SDK can do this for you or can connect to an existing Felt iframe.

Felt map IDs

Felt map IDs are unique identifiers for Felt maps. They are used to embed maps in iframes, and to connect to existing iframes.

To get the ID of a Felt map, click the Map settings button in the main toolbar, and then you can see the Map ID in the Developers section.

Alternatively, you can look at the URL of the map. For example, the map at https://felt.com/map/Map-title-xPV9BqMuYQxmUraVWy9C89BNA has the ID xPV9BqMuYQxmUraVWy9C89BNA.

Throughout the documentation, we'll use the placeholder FELT_MAP_ID to refer to a Felt map ID.

Using Felt.embed to create an iframe

Create an HTML page with a container element:

Embed a Felt map in your container element and use the SDK to control it by calling Felt.embed, passing the container element as the first argument:

Using Felt.embed to mount into an existing iframe

In some cases, you may want to add a "template" iframe to your page. This can be useful if you want to style your iframe in a specific way, or if you already have one map embedded and want to mount and control a different map.

In this case, you can call Felt.embed with the iframe element as the first argument:

Using Felt.connect to connect to an existing embedded Felt map

There may be cases where you already have a Felt map embedded in an iframe, and you want to control it using the SDK. This can be useful if your HTML is server-rendered with the Felt map already embedded.

In this case, you can call Felt.connect with the iframe's window as the first argument:

Note that in this case, you don't need to pass the Felt map ID to Felt.connect, because we are connecting to a map that has already been embedded.

The Felt SDK allows you to control your Felt maps and build powerful, interactive custom applications. You can control many aspects of the Felt UI and map contents, as well as receive notifications of events happening in the map such as clicks, selections, and more.

This feature is available to customers on the Enterprise plan. All new accounts automatically include a 7-day trial of Enterprise plan features.

See our examples page to explore what you can build with the SDK.

There are two main ways to use the Felt SDK:

1. Extensions

2. Embedded Maps

Extensions

Write code directly within Felt using our feature. Extensions run directly within the Felt environment, giving you immediate access to all SDK functionality without embedding or connection steps.

When creating an extension, you automatically have access to a object with no setup required. This controller provides all the methods you need to interact with your Felt map, including getViewport, createElement, setLayerStyle, and many more.

Embedded Maps

Embed Felt maps in your own applications and control them remotely. This approach requires connecting to a map embed.

Installation

Install the SDK using your preferred package manager:

Create an HTML page with a container element:

Embed a Felt map in your container element and use the SDK to control it:

For more information on how to control a map, see .

React Integration

If you are building a React application, you can use the to get started quickly.

You can also read our guide on to learn more about how to use the Felt SDK with React.

All calls to the Felt API require authorization using a Bearer token in the request header:

Authorization: Bearer <API Token>

These are tokens associated to your account only, and that you have to manually provide to the application you want to use.

Since these tokens grant access to your account, you must store them securely and treat them as a password to your account.

You can create an API token in the :

Be sure to take note of the token before closing the dialog; you won’t have a second chance to view it.

Once you have your API token, you can authenticate your requests to the Felt API by using it as a bearer token in your Authorization header:

Here's an example showing how to create a new Felt map:

The Felt REST API allows you to programmatically interact with the Felt platform, enabling you to integrate Felt's powerful mapping capabilities into your own workflows and pipelines.

You are able to create and manipulate Maps, Layers, Annotations, Sources, Projects and more.

This feature is available to customers on the . Reach out to .

Endpoints

All Felt API endpoints are hosted at the following base URL:

The Felt Style Language is a way for advanced users to style data quickly, through simple JSON code. This document is a guide to use as you test data files in Felt. For an exhaustive guide to all supported properties see the Reference Documentation.

Style definition blocks

Learn how to define and configure the code blocks that compose the Felt Style Language

A great way of building data-driven apps using Felt is by triggering a workflow whenever something changes on a map, like someone drawing a polygon around an area of interest or updating the details on a pin.

Instead of polling by listing annotations, comments or data layers on a fixed interval, a better alternative is to set up a webhook where Felt will send a notification any time a map is updated. This allows you to build integrations on top, such as sending a Slack message or performing calculations for the newly-drawn area.

Requirements

Two things are needed in order to make use of webhooks:

1. A Felt map which will serve as the basis for the webhook. Updates will be sent whenever something on this map changes.

2. A webhook URL where the updates will be sent in the form of POST requests.

Generating a new webhook

Workspace admins can set up webhooks in the .

Simply click on Create a new webhook, select a map to listen to changes and paste in a webhook URL where the updates will be sent to.

Using your new webhook

In order to use webhooks effectively, a receiving layer must be set up to trigger actions based on the updates sent by the Felt API. Here are some examples of how to set up a webhook using Felt and an external service.

This guide covers common patterns and concepts used throughout the Felt SDK.

By following these patterns consistently throughout the SDK, we aim to make the API predictable and easy to use while maintaining flexibility for future enhancements.

Use of promises

All methods in the Felt SDK are asynchronous and return Promises. This means you'll need to use await or .then() when calling them:

Getting entities

The SDK follows a consistent pattern for getting entities. For each entity type, there are usually two methods:

1. A singular getter for retrieving one entity by ID:

1. A plural getter that accepts constraints for retrieving multiple entities:

1. The plural getters allow you to pass no constraints, in which case they'll return all entities of that type:

Change listeners

Each entity type has a corresponding change listener method following the pattern on{EntityType}Change:

There are also various other setters and getters in the Felt SDK that follow this convention as much as possible. For example, selection:

And layer filters:

Cleanup functions

All change listeners return an unsubscribe function that should be called when you no longer need the listener:

This is particularly important in frameworks like React where you should clean up listeners when components unmount:

Handler and options structure

Change listeners always take a single object parameter containing both options and handler. This structure makes it easier to add new options in the future without breaking existing code:

Entity nodes

When dealing with mixed collections of entities (like in selection events), each entity is wrapped in an EntityNode object that includes type information:

It's common to have data update on a regular basis, such as every week or every month. Instead of having to re-upload and style the new data, it can be very convenient to simply refresh a layer using a new data source.

Refreshing a layer with a file

Just like , refreshing a layer with a new file is a two-step process:

1. Request a refresh via the Felt API

Perform a POST request to receive an S3 presigned URL which you can later upload your files to:

2. Upload your file(s) to Amazon s3

Refreshing a layer with a URL

Similar to , refreshing an existing URL layer is just a matter of making a single POST request:

Uploading a URL

The easiest way of uploading data into a Felt map via the API is to import from a URL. Here's an example importing all the recent earthquakes from :

Like maps, layers also have unique identifiers. Make sure to take note of them for subsequent calls, like styling a layer or removing it.

Uploading a file

Files aren't uploaded to the Felt app — instead, they're uploaded directly to Amazon S3. Therefore, creating a layer from a file on your computer is a two-step process:

1. Request an upload via the Felt API

Perform a POST request to receive an S3 presigned URL which you can later upload your files to:

2. Upload your file(s) to Amazon s3

Monitoring progress

You can check the upload status of a layer by querying it:

Understanding layer styles

A layer's style is defined in a JSON-based called the Felt Style Language, or FSL for short. Editors can view the current style of a layer inside a Felt map by clicking on Actions > Edit styles in a layer's overflow menu (three dots).

Here is an example of a simple visualization, expressed in FSL:

Fetching a layer's current style

A layer's FSL can be retrieved by performing a simple GET request to a layer's endpoint:

Updating an existing layer's style

To update a layer's style, we can send a POST request with the new FSL to the same layer's /update_style endpoint.

FSL examples

You can find examples of FSL for different visualization types in of these docs:

• : same color and size for all features (vector) or pixels (raster).

• : different color per feature or pixel, based on a categorical attribute

• : different color or size per feature or pixel, based on a numeric attribute.

The Felt SDK provides functionality for reading the current selection state and selecting features on the map programmatically. This is useful for building interactive experiences that respond to data analysis or user interactions.

Selecting Features

Features are individual data points within layers. You can select features programmatically using the method. Only one feature can be selected at a time - selecting a new feature will replace the current selection.

The method accepts options to control the selection behavior:

• showPopup (boolean, default: true) - Whether to display the feature information popup

• fitViewport (boolean | { maxZoom: number }, default: true) - Whether to fit the viewport to the feature. Can be true, false

Reading selection

You can get the current selection state using . This returns an array of objects, each representing a selected entity. The selection can include various types of entities at the same time, such as annotations and features:

Clearing Selection

Remove current selections using :

Reacting to selection changes

To stay in sync with selection changes, use the method:

Best practices

1. Clean up listeners: Always store and call the unsubscribe function when you no longer need to listen for selection changes:

1. Handle empty selection: Remember that the selection array might be empty if nothing is selected:

By following these patterns, you can build robust interactions based on what users select in your Felt map.

Workspaces and API tokens

Workspaces are the place where users in the same organization collaborate and share maps. A user may form part of several workspaces but, at the very least, always forms part of one.

API tokens are created per-workspace. If you wish to interact with several workspaces via the Felt API, you must create a different API token for each one.

The attributes block contains information on how attributes will be shown both on the popup and the table. Each attribute definition can contain the following properties:

The filters block contains information on how the layer is being filtered before displaying. In order for a feature to be shown on the map it must evaluate the filter expression to true.

Filters are written using a JSON infix notation that looks like one of [identifier, operator, operand], true or false .

• Valid identifiers are either a feature property or a nested expression.

Annotations live at the top layer of a map, and are created directly inside the Felt app.

Listing all annotations on a map

Annotations live at the top layer of a map, and are created directly inside the Felt app.

Annotations are returned as a .

Listing all annotation groups

Returns a list of GeoJSON Feature Collections, one for each annotation group.

Create or update new annotations

Each annotation is represented by a feature in the POSTed GeoJSON Feature Collection.

For each feature, including an existing annotation ID (felt:id) will result in the annotation being updated on the map. If no annotation ID is provided (or a non-existent one) , a new annotation will be created.

Delete an annotation

Annotations can be deleted by referencing them by ID

Simple visualizations are those that show each feature in a vector dataset using the same style or the image as it is in raster ones.

Simple visualizations must define "type": "simple" and a single value for each supported style and label properties.

Vector example

The Airports layer in Felt is an example of a simple visualization using a vector dataset

and is defined by the following style:

Raster example

This is an example of a simple visualization using a raster dataset

and is defined by the following style:

The Felt SDK provides several methods for reading data from your map's entities (layers, elements, etc.) and staying in sync with their changes. This guide will show you how to read entity data and react to changes.

Getting entities

The Felt SDK provides both singular and plural versions of getter methods for various entity types. This allows you to retrieve either a single entity or multiple entities of the same type.

For example, for layers:

Using constraints

All of the methods that return multiple entities accept constraint parameters to filter the results:

Reacting to changes

To stay in sync with entities, use the appropriate on[EntityType]Change method. For example, to monitor layer changes:

Best practices

1. Cleanup: Always store and call the unsubscribe functions when you're done listening for changes so that the listener doesn't continue to run in the background.

2. Error handling: When getting entities, remember that the methods may return null if the entity doesn't exist:

1. Batch operations: When you need multiple entities, use the bulk methods (getLayers, getElements, etc.) with constraints rather than making multiple individual calls:

This approach to reading and monitoring entities gives you full control over your map's data and allows you to build interactive applications that stay in sync with the map's state.

The popup block contains information on how the popup is displayed and which attributes to show.

These are the fields that each popup block can contain:

The legend block contains information on how the legend will be displayed for this visualization.

Take a look at the legends section to see how it works.

These are the fields that each legend block can contain:

"legend": {
  "displayName": {
    "category-1": "Category 1",
    "category-2": "Category 2"
  }
}

"legend": {
  "displayName": {
    "0": "-0.5", 
    "1": "0.5"
  }
}

Hillshades are used to visualize the valleys and ridges encoded in elevation raster data.

Hillshade visualizations are defined using “type”: “hillshade” and, support the following properties:

The following map is an example of a raster layer using a hillshade visualization

with the following style

Felt also supports adding color to hillshades by defining a color property in the style

which is defined by the following style

Most of the properties used on the style and label blocks can be defined using interpolators to enable zoom-based styling. Take a look at the full list of properties that can be interpolated in the full specification.

We support multiple types of interpolators: Step functions, linear, exponential and cubic bezier to enable your map looking like you want at each zoom level. See the Interpolators page.

An example of a layer changing feature colors depending on the zoom level can be found below

On zoom levels lower than 14, features of this layer will be rendered in red color. On zoom levels higher than 20, features of this layer will be rendered in blue color.

In zooms between 14 and 20, color will be linearly interpolated between red and blue.

Unexpected value or type

Problem: One of the values set in the style has an unsupported value or an invalid type.

Solution: Change the value to be valid.

Error messages:

• Attribute 'displayName' on a legend item of type simple must be a string.

• Attribute attribute_name is not a number.

• Attribute attribute_name is not a string.

• Attribute 'lineCap’ is not a supported value. Supported values are butt, round, square.

• Attribute 'lineJoin’ is not a supported value. Supported values are bevel, round, miter.

• Attribute ‘dashArray’ has to be a two-numbers array.

• Attribute 'offset' must be either an array of numbers or a number.

• Attribute 'placement' contains a not supported value. Supported values are N, NE, E, SE, S, SW, W, NW, Center.

• Attribute 'placement' contains a not supported value. Supported values are Above, Center, Below.

• All values in 'labelAttribute' must be a string.

• Visualization 'type' definition must be one of simple, categorical.

• Attribute 'showOther' must be one of above, below.

Categorical visualization not working

Problem: The style defines a categorical visualization, but the maps are not showing the layer

Error messages:

• Categories required. A categories array must be defined in the config block when defining a categorical visualization. Read more about categorical visualizations .

• Not enough or too many attribute_name values. When defining a categorical visualization, all style and label properties must be an array with either a single value that will apply to all categories or an array with as many values as categories defined in the config block. Read more about categorical visualizations .

Heatmaps are used to visualize the density of points on a map.

Heatmaps visualizations are defined using “type”: “heatmap” and, allow the following properties to be set:

This is an example of a heatmap visualization

defined with the following visualization

Heatmaps do not support labels.

The Felt SDK allows you to filter which features are visible in a layer using expressions that evaluate against feature properties. Filters can come from different sources and are combined to determine what's visible.

By understanding how filters work and combine, you can create dynamic views of your data that respond to user interactions and application state.

Understanding filter sources

Layer filters can come from multiple sources, which are combined to create the final filter:

To work with Felt embeds in React, we have a starter template that you can use as a starting point.

This is available on GitHub in the repository.

In that repo, you will find a feltUtils.ts file that demonstrates some ways to make using the Felt SDK in React easier.

Embedding with useFeltEmbed

H3 visualization is a way to aggregate point data into a grid of H3 cells.

H3 visualizations are defined using “type”: “h3” . They generally share the same properties and behaviors as . Properties of specific relevance to H3 are:

Explore examples of what you can build with the Felt SDK. These examples showcase different approaches to creating interactive map experiences - from extensions that run directly within Felt to embedded maps in custom applications.

Extensions

Extensions run directly within Felt maps, giving you immediate access to all SDK functionality. Here are some examples built using AI assistance:

Commuter patterns

Visualize transportation patterns by drawing lines to destination counties on click. Features travel mode options and filtering capabilities to analyze commuting data across different regions. View the map .

Neighborhood comparison

Compare neighborhoods side-by-side with automated analysis of land use patterns. This tool helps users understand demographic and geographic differences between areas. View the map .

Animated data

Bring geographic data to life with animations showing the flow of the Mississippi River Basin from headwaters to the Gulf of Mexico, demonstrating how to create compelling temporal visualizations. View the map .

Story map

Guide users through agricultural regions with an interactive narrative experience that combines storytelling with geographic exploration. View the map .

Embedded maps

Embed Felt maps in your own applications and control them with the SDK. Here are some examples built with React and hosted on CodeSandbox:

Rooftop Solar Potential

This interactive application leverages the Tool API to enable users to draw custom geometries that retrieve filtered GeoJSON data from an ESRI FeatureService. The application creates a dynamically styled GeoJSON layer to visualize solar potential data, helping users identify optimal locations for solar installations. View the app and code .

Sales Dashboard

Create powerful business intelligence tools by combining Felt's layer statistics with popular charting libraries. This example demonstrates how to build interactive visualizations that leverage layer filters. View the app and code .

Custom legend with nested folders

Enhance map usability with a custom legend that extracts and uses styling information to generate SVG icons. The code demonstrates how to build a nested folder structure with visibility toggles using layer filters, providing a pattern for organizing complex data layers. View the app and code .

Inset maps

Build comprehensive multi-view dashboards by embedding multiple Felt maps on a single page. This example demonstrates how to create synchronized map views that communicate with each other, enabling users to simultaneously view different geographic contexts or zoom levels of the same data. View the app and code .

Lens Map

Create engaging interactive experiences with customizable map lenses that reveal different data layers or styling as users explore. This technique allows for compelling before/after comparisons or the ability to highlight specific data attributes within a defined area. View the app and code .

Isochrones

Provides a pattern for integrating third-party geospatial APIs with Felt maps. This example demonstrates how to make API requests based on annotation geometry and map interactions, process the returned data, and visualise isochrones as dynamic layers. View the app and code .

Adding a legend block to a visualization makes a legend entry appear for this visualization.

Each legend entry is shown with the geometry type and color defined by the dataset and the visualization block.

While simple visualizations will generate a single legend entry, categorical visualizations will generate a legend entry per category.

To see how a legend is defined, take a look at the legend block section.

Simple legend

The Biodiversity Hotspots layer in Felt has a simple visualization with a legend defined as follows:

Categorical legend

The Plant Hardiness Zones layer in Felt has a categorical visualization with a legend defined as follows:

Numeric legends

The visual display of numeric legends varies based on the style method (stepped or continuous) and the geometry type (point, line, polygon).

The displayName can be modified in the legend block similar to simple and categorical style types.

Stepped

Continuous

Heatmap legends

Heatmap legends are defined as follows:

Notice that the displayName mapping goes from 0 (left value) to 1 (right value)

Categorical visualizations use a categorical attribute and the categories within it to apply styling to discrete categories of the attribute. On raster datasets, it uses a band instead of an attribute.

Categorical visualizations are defined using "type": "categorical" and, for every supported style and label property used, either a single value that will apply to all categories or an array of different values for each category.

Vector example

The Global Power Plants layer in Felt is an example of a categorical layer on a vector dataset

and is defined by the following style

Notice that we are saying that the primary_fuel data attribute will be used to categorize elements and that the possible values of that attribute that we are interested in are "Nuclear", "Oil", "Coal", "Gas", "Wind", "Hydro" and "Solar". Also notice that we are defining either a single value that will apply to all categories (i.e. size) or a value for each category (i.e. color)

Raster example

The Cropscape CDL layer in Felt is an example of a categorical layer on a raster dataset

and is defined by the following style:

The shape of a style definition

A style in its most basic form contains a version definition but it can be extended to define how we want geometry and labels to show on the map, how the legend should look like, what information is shown in popups and the formatting used when displaying feature properties.

The table below describes which properties can be used in the style definition.

The Felt SDK allows you to add GeoJSON data to your maps from various sources:

• Remote URLs

• Local files

• Programmatically generated GeoJSON data

The Felt SDK provides methods to control the map's viewport (the visible area of the map) and handle user interactions like clicking and hovering on the viewport.

Working with the viewport

Interpolators

Interpolators are functions that use the current zoom level to get you a value. The following interpolators are currently supported:

Step