Style categories (Map Viewer)

Map Viewer allows you to explore data in various ways through a variety of smart mapping styles. When you style map layers in Map Viewer, the nature of the data determines the default styling options. You can experiment with color ramps, line weights, transparency, symbols, and other graphic elements, and see your choices reflected immediately on the map.

To distribute your data by category, use the Types (unique symbols) style or the Types and Size style.

Types (unique symbols)

Use unique symbols to show various types of categorical data, not counts or numeric measurements. For example, you can use different colors to represent wind turbines by manufacturer.


There is an absolute limit of 200 unique values, although only 10 colors are used, so the same color may represent multiple categories. This means that unique symbols work best with 2 to 10 categories of data—for example, restaurant types, tree species, and political parties.

To style data by type using unique symbols, do the following:

  1. Follow the first four steps of Apply a style.
  2. In the Styles pane, click the Types (unique symbols) style if necessary and click Style options.

    To show time-based categories on the map, use the Discrete Time Periods (categories) style.

  3. Optionally, do any of the following:
    • Click a symbol under Symbol style to change all the map symbols at once, and specify the symbol options. For more information, see Use style options.
    • Click the colored symbol next to each category in the list to customize any of the categories individually. Depending on whether your data consists of points, lines, or areas, applicable styling options are shown for each type of symbol. For example, if your data consists of points, you can change the symbol shape, fill color, and outline.
    • Drag a category up or down in the list to reorder the categories.
    • Include fewer than 10 categories in a layer for best visualization; more than 10 are difficult to distinguish by color alone. If you include more than 10, only the 10 with the highest counts are shown. The remaining are automatically grouped into the Other category. If the counts of your features can't be determined, the first 9 categories are listed individually in alphabetical order, and the rest are grouped in the Other category. To ungroup the observations one at a time, drag them out of the Other list and into the main list, or click Move value out. To ungroup all of the observations at the same time, click Move all values out. To hide features in the Other category, uncheck the box. To show them, keep the box checked.
    • Click the color chip next to the category name to adjust the transparency applied to an individual category. Click Transparency by attribute to adjust the transparency of unique locations per feature, and specify the transparency settings. You can only use this option if you have numeric data associated with your locations. For example, if the layer contains restaurant sales data, you can style your data according to the type of restaurant and adjust the transparency of each category proportional to its annual sales.
    • You can rotate symbols based on a numeric attribute if you are mapping point symbols. For example, the color of the points can depict air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
  4. Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.

Types and Size

This style allows you to represent your data using different sizes and categories by color. Choose a text or numeric field for unique values and a numeric field for size values, and adjust each attribute's map symbol settings as needed. For example, in a map about unemployment in the United States, you can use this style to show a count attribute, such as the number of unemployed people per county, and use a unique color for each value found in another field, such as the state.

To style two attributes using unique values and size, do the following:

  1. Follow the first five steps of Apply a style.
  2. Choose a second attribute field or expression.
  3. Click the Types and Size style and click Style options.
  4. Select and apply options to Types (unique symbols) (first attribute) and Counts and Amounts (size) (second attribute).
  5. Click Done when you are finished customizing the style, or click Cancel to go back to the Styles pane without saving your choices.