Summary of the shapefile components used by ESRI

Shapefiles are a simple, non-topological format for storing the geometric location and attribute information of geographic features. The shapefile format defines the geometry and attributes of geographically referenced features in three or more files with specific file extensions that should be stored in the same project workspace. The essential rule of thumb is that whenever you copy, move or rename a .shp, you must do the same to all similarly named files or you risk data loss. The other files you may encounter are:

Required

• .shp - the file that stores the feature geometry.
• .shx - the file that stores the index of the feature geometry.
• .dbf - the dBASE file that stores the attribute information of features.

Optional

• .sbn and .sbx - the files that store the spatial index of the features.
• .fbn and .fbx - the files that store the spatial index of the features for shapefiles that are read-only.
• .ain and .aih - the files that store the attribute index of the active fields in a table or a theme's attribute table.
• .atx — An .atx file is created for each shapefile or dBASE attribute index created in ArcCatalog. ArcView 3.x (AV3) attribute indexes for shapefiles and dBASE files are not used by ArcGIS. A new attribute indexing model has been developed for shapefiles and dBASE files.
• .ixs — Geocoding index for read-write shapefiles.
• .mxs — Geocoding index for read-write shapefiles (ODB format).
• .prj - the file that stores the coordinate system information. This file can be created with and is used by the AV3 Projection Utility. It is not used by AV 3.0 or ArcInfo 8 and older (and some parts of ArcInfo v9 still don't use it). The .prj is a late addition to the Shapefile definition and is not present in the Original White paper.
• .xml - metadata for ArcInfo 8.0, for using shapefiles on the Internet.

For extended info and code on how gdal and related projects use shapefiles, see ​Shapelib

Sources

• ​Shapefile file extensions (2007)
• ​ESRI Shapefile Technical Description (1998)
• ​All extensions used by AV3 (uncategorized)
• ​The thread which spawned this wiki page
• ​Shapefile on Wikipedia