Reproject Shapefiles Online — Change CRS Without Desktop GIS

To reproject a shapefile online without QGIS or ArcGIS, first use Projection Finder to identify your shapefile's current CRS, then use a tool such as Mapshaper or MyGeodata Converter to convert it to your target EPSG code. Alternatively, a single ogr2ogr command — ogr2ogr -t_srs EPSG:4326 output.shp input.shp — handles reprojection locally in seconds.

Your Shapefile is in the wrong projection. Maybe it came from a colleague who works in a national grid, or you pulled it from a government portal that uses a local CRS, and now everything appears offset on your map. You need to reproject it — but you don't have QGIS installed, or you just want a faster path than opening desktop software.

This guide covers what reprojection actually does, how to identify your current CRS first (essential — skipping this step is the most common mistake), and the free tools that can handle the transformation online or from a single command.

What Reprojection Actually Does

Reprojection is not the same as assigning a CRS. This distinction matters enormously and gets confused constantly.

Operation	What Changes	When to Use
Assign / Define CRS	Metadata only — coordinate values stay the same	File has no .prj, but you know the correct CRS
Reproject	Coordinate values are mathematically transformed	File has the wrong CRS and features appear in the wrong place

When you reproject, every vertex in every feature gets its X and Y values recalculated. If your data is in British National Grid (EPSG:27700) and you reproject to WGS84 (EPSG:4326), those easting/northing values in the hundreds of thousands become decimal degrees between -90 and 90.

Assigning a CRS when you need to reproject — or reprojecting when you only need to assign — will make things worse, not better.

Step 1: Identify Your Current CRS

Before you reproject anything, you need to know the source CRS. Guessing is not an option — if you get this wrong, your reprojected output will be garbage.

The quickest check: open the .prj file that sits alongside your .shp file in a text editor. It contains WKT (Well-Known Text) describing the projection. Look for AUTHORITY["EPSG","XXXX"] — that number is your EPSG code.

If the .prj file is missing, empty, or you suspect it's wrong (data appears in the ocean, coordinates look like metres when you expect degrees), upload the Shapefile to Projection Finder. It reads the .prj metadata and also analyses the coordinate ranges to detect the most likely CRS — showing whether the result is FOUND (from metadata) or GUESSED (from coordinates).

Step 2: Choose Your Target CRS

For most web mapping work, WGS84 (EPSG:4326) is the right target. It's the standard geographic coordinate system used by GPS, GeoJSON, and most web APIs. Coordinates are decimal degrees (latitude/longitude).

If you're loading data into a web map tile service (Leaflet, Mapbox, Google Maps), you may need Web Mercator (EPSG:3857) instead — this is the projection behind all slippy-map tiles. Most libraries handle the conversion internally, but some require data in 3857 explicitly.

For analysis work — measuring areas, distances, buffers — stay in a projected CRS appropriate for your region. Reprojecting to WGS84 for analysis introduces distortion. Use a local UTM zone or national grid instead.

Free Online Tools for Reprojection

MapShaper (mapshaper.org)

MapShaper is the fastest browser-based option for most users. It handles Shapefiles, GeoJSON, CSV, and TopoJSON — and reprojection is built in.

1. Go to mapshaper.org
2. Drag all Shapefile components (.shp, .dbf, .prj, .shx) onto the page at the same time
3. Click Console (top right)
4. Type proj wgs84 and press Enter to reproject to WGS84, or proj +init=epsg:3857 for Web Mercator
5. Click Export, choose Shapefile, and download

MapShaper reads the existing .prj automatically as the source CRS. If your .prj is missing or wrong, the reprojection will be incorrect — which is why Step 1 matters.

For precise EPSG targets, use proj +init=epsg:XXXX where XXXX is any valid EPSG code.

MyGeodata Converter (mygeodata.cloud)

MyGeodata Converter takes a different approach: upload-based with a GUI dropdown for selecting the target CRS. It supports a wider range of obscure projections and can output multiple formats simultaneously.

1. Go to mygeodata.cloud/converter
2. Upload your Shapefile (zip the components together first)
3. Select your output format (Shapefile)
4. Under Coordinate System, search for your target EPSG code
5. Convert and download

The free tier has file size limits. For larger files, the command-line approach below is more practical.

Command-Line: ogr2ogr One-Liner

If you have GDAL installed (available via brew install gdal on macOS, or apt install gdal-bin on Ubuntu), ogr2ogr is the fastest and most reliable reprojection tool available.

Basic syntax: ogr2ogr -t_srs EPSG:4326 output.shp input.shp

This reads the CRS from the .prj file and reprojects to EPSG:4326. The -t_srs flag sets the target CRS.

If your source CRS is not in the .prj (or is wrong), override it with -s_srs: ogr2ogr -s_srs EPSG:27700 -t_srs EPSG:4326 output.shp input.shp

To reproject to Web Mercator: ogr2ogr -t_srs EPSG:3857 output.shp input.shp

ogr2ogr handles files of any size, preserves all attributes, and writes a correct .prj in the output. It also handles datum shifts automatically (important when converting between NAD27, NAD83, and WGS84).

QGIS Method (If You Have It)

If QGIS is available, the built-in reproject tool is straightforward and worth knowing:

1. Load your layer
2. Right-click the layer → Export → Save Features As
3. Under CRS, click the globe icon and search for your target EPSG code
4. Set the output file name and click OK

Note: right-clicking and choosing Set Layer CRS only assigns the CRS — it does not reproject. Use Save Features As with a different CRS to actually transform the coordinates.

Alternatively, use Vector → Data Management Tools → Reproject Layer from the menu for a dedicated dialog.

Common Mistakes

Assigning Instead of Reprojecting

The most frequent error. If you use Set Layer CRS in QGIS, or edit the .prj file manually, you are only changing the label — the coordinates remain unchanged. Features will jump to a different location on the map rather than being transformed correctly. Always use an export or reprojection tool that actually recalculates coordinates.

Losing Z Values

Some online tools strip the Z dimension (elevation) from 3D Shapefiles during reprojection. If your data has Z values, check the output before discarding the original. ogr2ogr preserves Z values by default; browser tools vary.

Ignoring Datum Shifts

Reprojecting from NAD27 to WGS84 is not a simple mathematical transformation — it requires a datum shift that can be metres to tens of metres depending on location. Tools like ogr2ogr apply the correct datum transformation automatically using PROJ's shift grids. Online tools may or may not handle this correctly. For precision surveying work, verify the datum transformation being applied.

Forgetting to Include the .prj File

When uploading to online tools, always include the .shp, .dbf, .shx, and .prj together (zip them). Without the .prj, the tool cannot determine the source CRS and may default to WGS84 — giving you a silently wrong result.

When This Does Not Help

Reprojection only works correctly when the source CRS is known and correct. If your data was created in the wrong projection to begin with (e.g., coordinates were recorded as if they were WGS84 but are actually UTM), reprojection will not fix the underlying data problem — it will just transform the wrong coordinates into a different wrong coordinate system.

Similarly, if the .prj file is present but contains incorrect information, tools that rely on it will reproject from the wrong starting point. Always verify the source CRS first — check that the data actually lands in the right place on a map before reprojecting.

Online tools are also not suitable for very large Shapefiles (multi-GB) or batch processing. For those cases, ogr2ogr scripted over a directory is the right approach.

FAQ

Summary

1. Identify your source CRS first — upload to Projection Finder or read the .prj file
2. Understand what you need — assigning changes metadata, reprojecting transforms coordinates
3. Choose WGS84 (EPSG:4326) as the target for web mapping; use a local projected CRS for analysis
4. Use MapShaper for quick browser-based reprojection — drag all Shapefile components and use the proj console command
5. Use ogr2ogr for larger files, batch processing, or when datum shifts need to be applied correctly
6. Verify the output — load the reprojected file and check that features appear in the correct location

Related Guides

• Find Shapefile Projection — Free .prj Checker & Fixer
• Fix GeoJSON Projection — Why Coordinates Show in the Ocean
• NAD83 vs WGS84 — What's the Difference?
• What Is a .prj File? The Shapefile Projection Guide
• Why Is My GIS Data Showing at 0,0?

Related Resources

• epsg.io — Look up any EPSG code or WKT definition
• mapshaper.org — Browser-based Shapefile reprojection and simplification
• spatialreference.org — EPSG and ESRI CRS reference database