Information for Style Authors

A style defines a map view’s content and appearance. If you’ve authored a style using Mapbox Studio’s Styles editor or as JSON in a text editor, you can use that style in this SDK and manipulate it afterwards in code. This document provides information you can use to ensure a seamless transition from Mapbox Studio to your application.

Designing for iOS

When designing your style, consider the context in which your application shows the style. There are a number of considerations specific to iOS that may not be obvious when designing your style in Mapbox Studio on the Web. A map view is essentially a graphical user interface element, so many of same issues in user interface design also apply when designing a map style.


Ensure sufficient contrast in your application’s user interface when your map style is present. Standard user interface elements such as toolbars, sidebars, and sheets often overlap the map view with a translucent, blurred background, so make sure the contents of these elements remain legible with the map view underneath. The user location annotation view, the attribution button, any buttons in callout views, and any items in the navigation bar are influenced by your application’s tint color, so choose a tint color that contrasts well with your map style. If you intend your style to be used in the dark, consider the impact that Night Shift may have on your style’s colors.

Typography and graphics

Choose font and icon sizes appropriate to iOS devices. iPhones and iPads have smaller screens than the typical browser window in which you would use Mapbox Studio, especially when multitasking is enabled. Your user’s viewing distance may be shorter than on a desktop computer. Some of your users may use the Larger Dynamic Type and Accessibility Text features to increase the size of all text on the device. You can use the runtime styling API to adjust your style’s font and icon sizes accordingly.

Design sprite images and choose font weights that look crisp on both standard-resolution displays and Retina displays. This SDK supports the same resolutions as iOS. Standard-resolution displays are limited to older devices that your application may or may not support, depending on its minimum deployment target.

Icon and text labels should be legible regardless of the map’s orientation. By default, this SDK makes it easy for your users to rotate or tilt the map using multitouch gestures. If you do not intend your design to accommodate rotation and tilting, disable these gestures using the MGLMapView.rotateEnabled and MGLMapView.pitchEnabled properties, respectively, or the corresponding inspectables in Interface Builder.


Pay attention to whether elements of your style appear to be interactive. A text label may look like a tappable button merely due to matching your application’s tint color or the default blue tint color. You can make an icon or text label interactive by installing a gesture recognizer and performing feature querying (e.g., -[MGLMapView visibleFeaturesAtPoint:]) to get details about the selected feature.

Make sure your users can easily distinguish any interactive elements from the surrounding map, such as pins, the user location annotation view, or a route line. Avoid relying on hover effects to indicate interactive elements. Leave enough room between interactive elements to accommodate imprecise tapping gestures.

For more information about user interface design, consult Apple’s iOS Human Interface Guidelines. To learn more about designing maps for mobile devices, see Nathaniel Slaughter’s blog post on the subject.

Applying your style

You set an MGLMapView object’s style either in code, by setting the MGLMapView.styleURL property, or in Interface Builder, by setting the “Style URL” inspectable. The URL must point to a local or remote style JSON file. The style JSON file format is defined by the Mapbox Style Specification. This SDK supports the functionality defined by version 8 of the specification unless otherwise noted in the style specification documentation.

Manipulating the style at runtime

The runtime styling API enables you to modify every aspect of a style dynamically as a user interacts with your application. The style itself is represented at runtime by an MGLStyle object, which provides access to various MGLSource and MGLStyleLayer objects that represent content sources and style layers, respectively. For more information about the capabilities exposed by the runtime styling API, see “Runtime Styling”.

The names of runtime styling classes and properties on iOS are generally consistent with the style specification and Mapbox Studio’s Styles editor. Any exceptions are listed in this document.

To avoid conflicts with Objective-C keywords or Cocoa terminology, this SDK uses the following terms for concepts defined in the style specification:

In the style specification In the SDK
bounds coordinate bounds
filter predicate
function type interpolation mode
id identifier
image style image
layer style layer
property attribute
SDF icon template image
source content source

Specifying the map’s content

Each source defined by a style JSON file is represented at runtime by a content source object that you can use to initialize new style layers. The content source object is a member of one of the following subclasses of MGLSource:

In style JSON In the SDK
vector MGLVectorTileSource
raster MGLRasterTileSource
raster-dem MGLRasterDEMSource
geojson MGLShapeSource
image MGLImageSource

canvas and video sources are not supported.

Tile sources

Raster and vector tile sources may be defined in TileJSON configuration files. This SDK supports the properties defined in the style specification, which are a subset of the keys defined in version 2.1.0 of the TileJSON specification. As an alternative to authoring a custom TileJSON file, you may supply various tile source options when creating a raster or vector tile source. These options are detailed in the MGLTileSourceOption documentation:

In style JSON In TileJSON In the SDK
url configurationURL parameter in -[MGLTileSource initWithIdentifier:configurationURL:]
tiles tiles tileURLTemplates parameter in -[MGLTileSource initWithIdentifier:tileURLTemplates:options:]
minzoom minzoom MGLTileSourceOptionMinimumZoomLevel
maxzoom maxzoom MGLTileSourceOptionMaximumZoomLevel
bounds bounds MGLTileSourceOptionCoordinateBounds
tileSize MGLTileSourceOptionTileSize
attribution attribution MGLTileSourceOptionAttributionHTMLString (but consider specifying MGLTileSourceOptionAttributionInfos instead for improved security)
scheme scheme MGLTileSourceOptionTileCoordinateSystem
encoding MGLTileSourceOptionDEMEncoding

Shape sources

Shape sources also accept various options. These options are detailed in the MGLShapeSourceOption documentation:

In style JSON In the SDK
data url parameter in -[MGLShapeSource initWithIdentifier:URL:options:]
maxzoom MGLShapeSourceOptionMaximumZoomLevel
buffer MGLShapeSourceOptionBuffer
tolerance MGLShapeSourceOptionSimplificationTolerance
cluster MGLShapeSourceOptionClustered
clusterRadius MGLShapeSourceOptionClusterRadius
clusterMaxZoom MGLShapeSourceOptionMaximumZoomLevelForClustering
lineMetrics MGLShapeSourceOptionLineDistanceMetrics

To create a shape source from local GeoJSON data, first convert the GeoJSON data into a shape, then use the -[MGLShapeSource initWithIdentifier:shape:options:] method.

Image sources

Image sources accept a non-axis aligned quadrilateral as their geographic coordinates. These coordinates, in MGLCoordinateQuad, are described in counterclockwise order, in contrast to the clockwise order defined in the style specification.

Configuring the map content’s appearance

Each layer defined by the style JSON file is represented at runtime by a style layer object, which you can use to refine the map’s appearance. The style layer object is a member of one of the following subclasses of MGLStyleLayer:

In style JSON In the SDK
background MGLBackgroundStyleLayer
circle MGLCircleStyleLayer
fill MGLFillStyleLayer
fill-extrusion MGLFillExtrusionStyleLayer
heatmap MGLHeatmapStyleLayer
hillshade MGLHillshadeStyleLayer
line MGLLineStyleLayer
raster MGLRasterStyleLayer
symbol MGLSymbolStyleLayer

You configure layout and paint attributes by setting properties on these style layer objects. The property names generally correspond to the style JSON properties, except for the use of camelCase instead of kebab-case. Properties whose names differ from the style specification are listed below:

Circle style layers

In style JSON In Objective-C In Swift
circle-pitch-scale MGLCircleStyleLayer.circleScaleAlignment MGLCircleStyleLayer.circleScaleAlignment
circle-translate MGLCircleStyleLayer.circleTranslation MGLCircleStyleLayer.circleTranslation
circle-translate-anchor MGLCircleStyleLayer.circleTranslationAnchor MGLCircleStyleLayer.circleTranslationAnchor

Fill style layers

In style JSON In Objective-C In Swift
fill-antialias MGLFillStyleLayer.fillAntialiased MGLFillStyleLayer.isFillAntialiased
fill-translate MGLFillStyleLayer.fillTranslation MGLFillStyleLayer.fillTranslation
fill-translate-anchor MGLFillStyleLayer.fillTranslationAnchor MGLFillStyleLayer.fillTranslationAnchor

Fill extrusion style layers

In style JSON In Objective-C In Swift
fill-extrusion-vertical-gradient MGLFillExtrusionStyleLayer.fillExtrusionHasVerticalGradient MGLFillExtrusionStyleLayer.fillExtrusionHasVerticalGradient
fill-extrusion-translate MGLFillExtrusionStyleLayer.fillExtrusionTranslation MGLFillExtrusionStyleLayer.fillExtrusionTranslation
fill-extrusion-translate-anchor MGLFillExtrusionStyleLayer.fillExtrusionTranslationAnchor MGLFillExtrusionStyleLayer.fillExtrusionTranslationAnchor

Line style layers

In style JSON In Objective-C In Swift
line-dasharray MGLLineStyleLayer.lineDashPattern MGLLineStyleLayer.lineDashPattern
line-translate MGLLineStyleLayer.lineTranslation MGLLineStyleLayer.lineTranslation
line-translate-anchor MGLLineStyleLayer.lineTranslationAnchor MGLLineStyleLayer.lineTranslationAnchor

Raster style layers

In style JSON In Objective-C In Swift
raster-brightness-max MGLRasterStyleLayer.maximumRasterBrightness MGLRasterStyleLayer.maximumRasterBrightness
raster-brightness-min MGLRasterStyleLayer.minimumRasterBrightness MGLRasterStyleLayer.minimumRasterBrightness
raster-hue-rotate MGLRasterStyleLayer.rasterHueRotation MGLRasterStyleLayer.rasterHueRotation
raster-resampling MGLRasterStyleLayer.rasterResamplingMode MGLRasterStyleLayer.rasterResamplingMode

Symbol style layers

In style JSON In Objective-C In Swift
icon-allow-overlap MGLSymbolStyleLayer.iconAllowsOverlap MGLSymbolStyleLayer.iconAllowsOverlap
icon-ignore-placement MGLSymbolStyleLayer.iconIgnoresPlacement MGLSymbolStyleLayer.iconIgnoresPlacement
icon-image MGLSymbolStyleLayer.iconImageName MGLSymbolStyleLayer.iconImageName
icon-optional MGLSymbolStyleLayer.iconOptional MGLSymbolStyleLayer.isIconOptional
icon-rotate MGLSymbolStyleLayer.iconRotation MGLSymbolStyleLayer.iconRotation
icon-size MGLSymbolStyleLayer.iconScale MGLSymbolStyleLayer.iconScale
icon-keep-upright MGLSymbolStyleLayer.keepsIconUpright MGLSymbolStyleLayer.keepsIconUpright
text-keep-upright MGLSymbolStyleLayer.keepsTextUpright MGLSymbolStyleLayer.keepsTextUpright
text-max-angle MGLSymbolStyleLayer.maximumTextAngle MGLSymbolStyleLayer.maximumTextAngle
text-max-width MGLSymbolStyleLayer.maximumTextWidth MGLSymbolStyleLayer.maximumTextWidth
symbol-avoid-edges MGLSymbolStyleLayer.symbolAvoidsEdges MGLSymbolStyleLayer.symbolAvoidsEdges
text-field MGLSymbolStyleLayer.text MGLSymbolStyleLayer.text
text-allow-overlap MGLSymbolStyleLayer.textAllowsOverlap MGLSymbolStyleLayer.textAllowsOverlap
text-font MGLSymbolStyleLayer.textFontNames MGLSymbolStyleLayer.textFontNames
text-size MGLSymbolStyleLayer.textFontSize MGLSymbolStyleLayer.textFontSize
text-ignore-placement MGLSymbolStyleLayer.textIgnoresPlacement MGLSymbolStyleLayer.textIgnoresPlacement
text-justify MGLSymbolStyleLayer.textJustification MGLSymbolStyleLayer.textJustification
text-optional MGLSymbolStyleLayer.textOptional MGLSymbolStyleLayer.isTextOptional
text-rotate MGLSymbolStyleLayer.textRotation MGLSymbolStyleLayer.textRotation
text-writing-mode MGLSymbolStyleLayer.textWritingModes MGLSymbolStyleLayer.textWritingModes
icon-translate MGLSymbolStyleLayer.iconTranslation MGLSymbolStyleLayer.iconTranslation
icon-translate-anchor MGLSymbolStyleLayer.iconTranslationAnchor MGLSymbolStyleLayer.iconTranslationAnchor
text-translate MGLSymbolStyleLayer.textTranslation MGLSymbolStyleLayer.textTranslation
text-translate-anchor MGLSymbolStyleLayer.textTranslationAnchor MGLSymbolStyleLayer.textTranslationAnchor

Setting attribute values

Each property representing a layout or paint attribute is set to an NSExpression object. NSExpression objects play the same role as expressions in the Mapbox Style Specification, but you create the former using a very different syntax. NSExpression’s format string syntax is reminiscent of a spreadsheet formula or an expression in a database query. See the “Predicates and Expressions” guide for an overview of the expression support in this SDK. This SDK no longer supports style functions; use expressions instead.

Constant values in expressions

In contrast to the JSON type that the style specification defines for each layout or paint property, the style value object often contains a more specific Foundation or Cocoa type. General rules for attribute types are listed below. Pay close attention to the SDK documentation for the attribute you want to get or set.

In style JSON In Objective-C In Swift
Color UIColor UIColor
Enum NSString String
String NSString String
Boolean NSNumber.boolValue NSNumber.boolValue
Number NSNumber.floatValue NSNumber.floatValue
Array (-dasharray) NSArray<NSNumber> [Float]
Array (-font) NSArray<NSString> [String]
Array (-offset, -translate) NSValue.CGVectorValue NSValue.cgVectorValue
Array (-padding) NSValue.UIEdgeInsetsValue NSValue.uiEdgeInsetsValue

For padding attributes, note that the arguments to UIEdgeInsetsMake() in Objective-C and UIEdgeInsets(top:left:bottom:right:) in Swift are specified in counterclockwise order, in contrast to the clockwise order defined by the style specification.

Expression operators

Many expression operators defined in the style specification have corresponding symbols to be used with the +[NSExpression expressionWithFormat:], +[NSExpression expressionForFunction:arguments:], or +[NSExpression expressionForFunction:selectorName:arguments:] method:

In style specification Method, function, or predicate type Format string syntax
collator NSComparisonPredicateOptions 'Québec' =[cd] 'QUEBEC'
literal +[NSExpression expressionForConstantValue:] %@ representing NSArray or NSDictionary
to-boolean boolValue
to-color CAST(var, 'UIColor')
to-number mgl_numberWithFallbackValues: CAST(zipCode, 'NSNumber')
to-string stringValue CAST(ele, 'NSString')
geometry-type NSExpression.geometryTypeVariableExpression $geometryType
id NSExpression.featureIdentifierVariableExpression $featureIdentifier
properties NSExpression.featureAttributesVariableExpression $featureAttributes
at objectFrom:withIndex: array[n]
get +[NSExpression expressionForKeyPath:] Key path
has mgl_does:have: mgl_does:have:(self, 'key')
in NSInPredicateOperatorType needle IN haystack or haystack CONTAINS needle or ANY haystack = needle
length count: count({1, 2, 2, 3, 4, 7, 9})
! NSNotPredicateType NOT (p0 OR … OR pn)
!= NSNotEqualToPredicateOperatorType key != value
< NSLessThanPredicateOperatorType key < value
<= NSLessThanOrEqualToPredicateOperatorType key <= value
== NSEqualToPredicateOperatorType key == value
> NSGreaterThanPredicateOperatorType key > value
>= NSGreaterThanOrEqualToPredicateOperatorType key >= value
all NSAndPredicateType p0 AND … AND pn
any NSOrPredicateType p0 OR … OR pn
case +[NSExpression expressionForConditional:trueExpression:falseExpression:] or MGL_IF or +[NSExpression mgl_expressionForConditional:trueExpression:falseExpresssion:] TERNARY(1 = 2, YES, NO) or MGL_IF(1 = 2, YES, 2 = 2, YES, NO)
coalesce mgl_coalesce: mgl_coalesce({x, y, z})
match MGL_MATCH or +[NSExpression mgl_expressionForMatchingExpression:inDictionary:defaultExpression:] MGL_MATCH(x, 0, 'zero match', 1, 'one match', 'two match', 'default')
within NSInPredicateOperatorType SELF IN %@ or %@ CONTAINS SELF where %@ is an MGLShape
interpolate mgl_interpolate:withCurveType:parameters:stops: or +[NSExpression mgl_expressionForInterpolatingExpression:withCurveType:parameters:stops:]
step mgl_step:from:stops: or +[NSExpression mgl_expressionForSteppingExpression:fromExpression:stops:]
let mgl_expressionWithContext: MGL_LET('ios', 11, 'macos', 10.13, $ios + $macos)
var +[NSExpression expressionForVariable:] $variable
concat mgl_join: or -[NSExpression mgl_expressionByAppendingExpression:] mgl_join({'Old', ' ', 'MacDonald'})
downcase lowercase: lowercase('DOWNTOWN')
upcase uppercase: uppercase('Elysian Fields')
rgb +[UIColor colorWithRed:green:blue:alpha:]
rgba +[UIColor colorWithRed:green:blue:alpha:]
to-rgba CAST(noindex(var), 'NSArray')
- from:subtract: 2 - 1
* multiply:by: 1 * 2
/ divide:by: 1 / 2
% modulus:by:
^ raise:toPower: 2 ** 2
+ add:to: 1 + 2
abs abs: abs(-1)
acos mgl_acos: mgl_acos(1)
asin mgl_asin: mgl_asin(0)
atan mgl_atan: mgl_atan(20)
ceil ceiling: ceiling(0.99999)
cos mgl_cos: mgl_cos(0)
distance mgl_distanceFrom(%@) where %@ is an MGLShape
e %@ representing NSNumber containing M_E
floor floor: floor(-0.99999)
ln ln: ln(2)
ln2 %@ representing NSNumber containing M_LN2
log10 log: log(1)
log2 mgl_log2: mgl_log2(1024)
max max: max({1, 2, 2, 3, 4, 7, 9})
min min: min({1, 2, 2, 3, 4, 7, 9})
pi %@ representing NSNumber containing M_PI
round mgl_round: mgl_round(1.5)
sin mgl_sin: mgl_sin(0)
sqrt sqrt: sqrt(2)
tan mgl_tan: mgl_tan(0)
zoom NSExpression.zoomLevelVariableExpression $zoomLevel
heatmap-density NSExpression.heatmapDensityVariableExpression $heatmapDensity
line-progress NSExpression.lineProgressVariableExpression $lineProgress
format +[NSExpression mgl_expressionForAttributedExpressions:] or mgl_attributed: mgl_attributed({x, y, z})

For operators that have no corresponding NSExpression symbol, use the MGL_FUNCTION() format string syntax.

Filtering sources

You can filter a shape or vector tile source by setting the MGLVectorStyleLayer.predicate property to an NSPredicate object. Below is a table of style JSON operators and the corresponding operators used in the predicate format string:

In style JSON In the format string
["has", key] key != nil
["!has", key] key == nil
["==", key, value] key == value
["!=", key, value] key != value
[">", key, value] key > value
[">=", key, value] key >= value
["<", key, value] key < value
["<=", key, value] key <= value
["in", key, v0, …, vn] key IN {v0, …, vn}
["!in", key, v0, …, vn] NOT key IN {v0, …, vn}
["all", f0, …, fn] p0 AND … AND pn
["any", f0, …, fn] p0 OR … OR pn
["none", f0, …, fn] NOT (p0 OR … OR pn)

Specifying the text format

The following format attributes are defined as NSString constans that you can use to update the formatting of MGLSymbolStyleLayer.text property.

In style JSON In Objective-C In Swift
text-font MGLFontNamesAttribute .fontNamesAttribute
font-scale MGLFontScaleAttribute .fontScaleAttribute
text-color MGLFontColorAttribute .fontColorAttribute

See the “Predicates and Expressions” guide for a full description of the supported operators and operand types.