diff --git a/docs/source/publishing/ogcapi-maps.rst b/docs/source/publishing/ogcapi-maps.rst
index 6924e3a39..a6b2aca1f 100644
--- a/docs/source/publishing/ogcapi-maps.rst
+++ b/docs/source/publishing/ogcapi-maps.rst
@@ -113,6 +113,15 @@ required.  An optional style name can be defined via `options.style`.
                name: png
                mimetype: image/png
 
+.. note::
+  According to the `Standard <https://docs.ogc.org/is/20-058/20-058.html#_5df53b56-5468-4c9d-acac-6abfddd83ccf>`_, OGC API - Maps
+  supports a `crs` parameter, expressed as an uri. Currently, this provider supports WGS84 and Web Mercator; for a matter of convenience, they can be expressed in
+  a number of different ways, other than the uri format.
+
+  - `EPSG:4326`
+  - `EPSG:3857`
+  - `4326`
+  - `3857`
 
 Data visualization examples
 ---------------------------
diff --git a/pygeoapi/api/maps.py b/pygeoapi/api/maps.py
index 8712e4c94..6af162a0b 100644
--- a/pygeoapi/api/maps.py
+++ b/pygeoapi/api/maps.py
@@ -61,9 +61,17 @@
     'http://www.opengis.net/spec/ogcapi-maps-1/1.0/conf/core'
 ]
 
-
 DEFAULT_CRS = 'http://www.opengis.net/def/crs/EPSG/0/4326'
 
+CRS_CODES = {
+    '4326': 'http://www.opengis.net/def/crs/EPSG/0/4326',
+    '3857': 'http://www.opengis.net/def/crs/EPSG/0/3857',
+    'http://www.opengis.net/def/crs/EPSG/0/4326': 'http://www.opengis.net/def/crs/EPSG/0/4326',  # noqa
+    'http://www.opengis.net/def/crs/EPSG/0/3857': 'http://www.opengis.net/def/crs/EPSG/0/3857',  # noqa
+    'EPSG:4326': 'http://www.opengis.net/def/crs/EPSG/0/4326',
+    'EPSG:3857': 'http://www.opengis.net/def/crs/EPSG/0/3857',
+}
+
 
 def get_collection_map(api: API, request: APIRequest,
                        dataset: str, style: str | None = None
@@ -106,10 +114,10 @@ def get_collection_map(api: API, request: APIRequest,
 
     query_args['format_'] = request.params.get('f', 'png')
     query_args['style'] = style
-    query_args['crs'] = collection_def.get('crs', DEFAULT_CRS)
-    query_args['bbox_crs'] = request.params.get(
-        'bbox-crs', DEFAULT_CRS
-    )
+    query_args['crs'] = CRS_CODES[request.params.get(
+        'crs', collection_def.get('crs', DEFAULT_CRS))]
+    query_args['bbox_crs'] = CRS_CODES[request.params.get(
+        'bbox-crs', collection_def.get('crs', DEFAULT_CRS))]
     query_args['transparent'] = request.params.get('transparent', True)
 
     try:
@@ -151,6 +159,7 @@ def get_collection_map(api: API, request: APIRequest,
         return headers, HTTPStatus.BAD_REQUEST, to_json(
             exception, api.pretty_print)
 
+    # the transformer function expects the crs to be in a uri format
     if query_args['bbox_crs'] != query_args['crs']:
         LOGGER.debug(f'Reprojecting bbox CRS: {query_args["crs"]}')
         bbox = transform_bbox(bbox, query_args['bbox_crs'], query_args['crs'])
diff --git a/pygeoapi/provider/wms_facade.py b/pygeoapi/provider/wms_facade.py
index e96f3c244..8c1507c49 100644
--- a/pygeoapi/provider/wms_facade.py
+++ b/pygeoapi/provider/wms_facade.py
@@ -42,7 +42,6 @@
 }
 
 CRS_CODES = {
-    4326: 'EPSG:4326',
     'http://www.opengis.net/def/crs/EPSG/0/4326': 'EPSG:4326',
     'http://www.opengis.net/def/crs/EPSG/0/3857': 'EPSG:3857'
 }