# Module: ol/proj/proj4

This documentation is for OpenLayers v10.9.0. The latest is v.

## ol/proj/proj4

### Functions

#### epsgLookupMapTiler(key){function}

proj/proj4.js, line 231

      import {epsgLookupMapTiler} from 'ol/proj/proj4';

  Generate an EPSG lookup function which uses the MapTiler Coordinates API to find projection definitions which do not require proj4 to be configured to handle `+nadgrids` parameters. Call `setEPSGLookup` use the function for lookups `setEPSGLookup(epsgLookupMapTiler('{YOUR_MAPTILER_API_KEY_HERE}'))`.

  Name | Type | Description
  --- | --- | ---
  `key` | string | MapTiler API key. Get your own API key at https://www.maptiler.com/cloud/.

  Deprecated
    - Not needed any more, the default lookup provides this functionality now.

  ##### Returns:

  The EPSG lookup function.

#### fromEPSGCode(code){Promise<Projection>}

proj/proj4.js, line 213

      import {fromEPSGCode} from 'ol/proj/proj4';

  Get a projection from an EPSG code. This function fetches the projection definition from the spatialreference.org website, registers this definition for use with proj4, and returns a configured projection. You must call import proj4 and call `register` before using this function.

  If the projection definition is already registered with proj4, it will not be fetched again (so it is ok to call this function multiple times with the same code).

  Name | Type | Description
  --- | --- | ---
  `code` | number | string | The EPSG code (e.g. 4326 or 'EPSG:4326').

  Deprecated
    - Use `fromProjectionCode` instead.

  ##### Returns:

  The projection.

#### fromProjectionCode(code){Promise<Projection>}

proj/proj4.js, line 148

      import {fromProjectionCode} from 'ol/proj/proj4';

  Get a projection from a projection code (i.e., authority:number). This function fetches the projection definition from the https://spatialreference.org website, registers this definition for use with proj4, and returns a configured projection. You must call import proj4 and call `register` before using this function.

  If the projection definition is already registered with proj4, it will not be fetched again (so it is ok to call this function multiple times with the same code).

  Name | Type | Description
  --- | --- | ---
  `code` | string | The projection code (e.g., 'EPSG:4326' or 'OGC:CRS84').

  ##### Returns:

  The projection.

#### register(proj4)

proj/proj4.js, line 44

      import {register} from 'ol/proj/proj4';

  Make projections defined in proj4 (with `proj4.defs()`) available in OpenLayers. Requires proj4 >= 2.8.0.

  This function should be called whenever changes are made to the proj4 registry, e.g. after calling `proj4.defs()`. Existing transforms will not be modified by this function.

  Name | Type | Description
  --- | --- | ---
  `proj4` | module:proj4 | Proj4.

#### setEPSGLookup(func)

proj/proj4.js, line 183

      import {setEPSGLookup} from 'ol/proj/proj4';

  Set the lookup function for getting proj4 or WKT definitions given an EPSG code. By default, the `fromEPSGCode` function uses the spatialreference.org website for WKT definitions. This can be changed by providing a different lookup function.

  Name | Type | Description
  --- | --- | ---
  `func` | function | The lookup function.

  Deprecated
    - Use `setProjectionCodeLookup` instead.

#### setProjectionCodeLookup(func)

proj/proj4.js, line 120

      import {setProjectionCodeLookup} from 'ol/proj/proj4';

  Set the lookup function for getting proj4 or WKT definitions given an projection code. By default, the `fromProjectionCode` function uses the spatialreference.org website for WKT definitions. This can be changed by providing a different lookup function.

  Name | Type | Description
  --- | --- | ---
  `func` | function | The lookup function.