Apply a reducer over the area of each feature in the given collection.

The reducer must have the same number of inputs as the input image has bands.

Returns the input features, each augmented with the corresponding reducer outputs.

Image.reduceRegions(collection, reducer, scale, crs, crsTransform, tileScale)FeatureCollection
this: imageImageThe image to reduce.
collectionFeatureCollectionThe features to reduce over.
reducerReducerThe reducer to apply.
scaleFloat, default: nullA nominal scale in meters of the projection to work in.
crsProjection, default: nullThe projection to work in. If unspecified, the projection of the image's first band is used. If specified in addition to scale, rescaled to the specified scale.
crsTransformList, default: nullThe list of CRS transform values. This is a row-major ordering of the 3x2 transform matrix. This option is mutually exclusive with 'scale', and will replace any transform already set on the projection.
tileScaleFloat, default: 1A scaling factor used to reduce aggregation tile size; using a larger tileScale (e.g. 2 or 4) may enable computations that run out of memory with the default.


Code Editor (JavaScript)

// A Landsat 8 SR image with SWIR1, NIR, and green bands.
var img = ee.Image('LANDSAT/LC08/C02/T1_L2/LC08_044034_20210508')
              .select(['SR_B6', 'SR_B5', 'SR_B3']);

// Santa Cruz Mountains ecoregions feature collection.
var regionCol = ee.FeatureCollection('EPA/Ecoregions/2013/L4')
                    .filter('us_l4name == "Santa Cruz Mountains" || ' +
                            'us_l4name == "San Mateo Coastal Hills" || ' +
                            'us_l4name == "Leeward Hills"');

// Display layers on the map.
Map.setCenter(-122.08, 37.22, 9);
Map.addLayer(img, {min: 10000, max: 20000}, 'Landsat image');
Map.addLayer(regionCol, {color: 'white'}, 'Santa Cruz Mountains ecoregions');

// Calculate median band values within Santa Cruz Mountains ecoregions. It is
// good practice to explicitly define "scale" (or "crsTransform") and "crs"
// parameters of the analysis to avoid unexpected results from undesired
// defaults when e.g. reducing a composite image.
var stats = img.reduceRegions({
  collection: regionCol,
  reducer: ee.Reducer.median(),
  scale: 30,  // meters
  crs: 'EPSG:3310',  // California Albers projection

// The input feature collection is returned with new properties appended.
// The new properties are the outcome of the region reduction per image band,
// for each feature in the collection. Region reduction property names
// are the same as the input image band names.
print('Median band values, Santa Cruz Mountains ecoregions', stats);

// You can combine reducers to calculate e.g. mean and standard deviation
// simultaneously. The resulting property names are the concatenation of the
// band names and statistic names, separated by an underscore.
var reducer = ee.Reducer.mean().combine({
  reducer2: ee.Reducer.stdDev(),
  sharedInputs: true
var multiStats = img.reduceRegions({
  collection: regionCol,
  reducer: reducer,
  scale: 30,
  crs: 'EPSG:3310',
print('Mean & SD band values, Santa Cruz Mountains ecoregions', multiStats);