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Search an EPSG code to see the CRS name, PROJ string, WKT, area of use, and map preview.
EPSG Codes and Coordinate Reference Systems
An EPSG code is a numeric identifier for a coordinate reference system. GIS software uses it to know whether coordinates are latitude and longitude, Web Mercator meters, a national grid, or a local projected coordinate system. The right code keeps map layers aligned in QGIS, ArcGIS, PostGIS, GDAL, web maps, and survey workflows.
What Is an EPSG Code?
EPSG codes come from the EPSG Geodetic Parameter Dataset. A code points to a CRS definition, including datum, coordinate axes, map projection method, units, and area of use. EPSG:4326 is WGS 84 latitude and longitude. EPSG:3857 is the Web Mercator projection used by most web map tiles. EPSG:32633 is WGS 84 UTM zone 33 north, a projected CRS measured in meters.
How to Look Up a Coordinate Reference System
Start with the code when you have one. Search 4326, EPSG:3857, or 32632 to get a direct CRS record. When you only know the name, search terms like Web Mercator, British National Grid, NAD83, or UTM zone 32N. A good EPSG lookup should show the official CRS name, kind, datum, units, area of use, and copy-ready projection definitions.
EPSG:4326 vs EPSG:3857
EPSG:4326
WGS 84 geographic coordinates. Values are longitude and latitude angles in degrees. Use it for GPS data, GeoJSON coordinates, and global position storage.
EPSG:3857
WGS 84 Pseudo-Mercator projected coordinates. Values are meters in a web mapping projection. Use it for slippy maps and tile layers, not precision distance or area measurement.
Using EPSG Codes in QGIS, ArcGIS, PostGIS, and GDAL
In QGIS and ArcGIS, EPSG codes define the layer CRS and project CRS. In PostGIS, use ST_SetSRID(geom, 4326) to tag geometry and ST_Transform(geom, 3857) to reproject it. In GDAL, commands like ogr2ogr -t_srs EPSG:3857 transform datasets into a target CRS. The EPSG code is the shared language that keeps these systems consistent.
What Are PROJ Strings and WKT Definitions?
A PROJ string is a compact projection definition used by the PROJ library and many command-line GIS tools. WKT, or Well-Known Text, is a more complete structured CRS definition. Modern GIS software usually prefers EPSG codes or WKT, while PROJ strings remain useful for scripts, legacy tools, and quick debugging.
Common EPSG Codes for GIS Projects
| EPSG | CRS name | Typical use |
|---|---|---|
| EPSG:4326 | WGS 84 | GPS latitude and longitude |
| EPSG:3857 | WGS 84 / Pseudo-Mercator | Web maps and tile services |
| EPSG:4979 | WGS 84 3D | GPS latitude, longitude, and height |
| EPSG:32633 | WGS 84 / UTM zone 33N | Metric mapping in UTM zone 33 north |
| EPSG:32756 | WGS 84 / UTM zone 56S | Metric mapping in UTM zone 56 south |
| EPSG:27700 | OSGB36 / British National Grid | Great Britain mapping |
| EPSG:5070 | NAD83 / Conus Albers | US national thematic mapping |
| EPSG:2193 | NZGD2000 / New Zealand Transverse Mercator | New Zealand mapping |
EPSG Code Lookup FAQ
Is EPSG:900913 official?
No. EPSG:900913 was an informal Web Mercator alias used historically by web map developers. Use EPSG:3857 in modern GIS software.
Can I measure distance in EPSG:4326?
EPSG:4326 uses degrees, so direct planar distance calculations are not appropriate. Transform to a suitable projected CRS such as UTM, a national grid, or an equal-area/equidistant projection first.
Which CRS should I use for a local project?
Use the official national or regional CRS when one exists. If not, WGS 84 UTM is often a practical metric choice, as long as your project fits mostly within one UTM zone.