GIS Tools - GIS Clip Tool (Clip Layer by Polygon)

What Is a GIS Clip Operation?

Clipping in GIS extracts the portion of one layer that falls inside a polygon boundary from another layer. It's the digital equivalent of using a cookie cutter: the clip layer defines the shape of the cutter, and the input layer supplies the dough that gets cut. The result contains only features (or parts of features) inside the cutter, with the original attributes from the input layer intact. Clip layer GIS workflows are among the most common geoprocessing operations alongside buffer and intersect, and every desktop and server GIS exposes them under names like Clip, Extract by Mask, or ST_Intersection.

The GIS Clip Tool on gis.tools lets you clip polygon by polygon, clip lines by polygon, or clip points by polygon directly in your browser. Drag both layers in, click Clip, and export the result. There is no need to install QGIS, pay for an ArcGIS license, or stand up a PostGIS server. Because everything runs client-side, confidential input data stays on your machine.

Clip is often confused with intersect. The two operations produce similar geometries, but clip keeps only the input layer's attributes, whereas intersect carries attributes from both layers forward into the result. If you only need geometry extraction without attribute joining, clip is faster and cleaner.

How Clipping Works

The clip algorithm walks through each feature in the input layer and computes its geometric intersection with the clip polygon. Features fully inside the clip boundary are kept unchanged. Features fully outside are discarded. Features that cross the boundary are cut precisely along the edge, producing partial geometries whose shape traces the clip polygon wherever the input would otherwise extend beyond it.

Internally, clipping relies on the same polygon-clipping algorithms used in computer graphics and computational geometry: Sutherland-Hodgman for convex cases, Weiler-Atherton and Vatti for general cases, and the Martinez-Rueda variant used by many modern libraries including GEOS, JTS, and polyclip. All of these produce topologically correct output as long as both inputs are valid.

Line Clipping

Line clipping produces segments. A road that enters a city boundary, passes through, and exits on the other side becomes two separate line features if clipped by that boundary (or a single connected line if the city is convex).

Point Clipping

Point clipping is trivially a point-in-polygon test. Points inside the clip polygon are kept; points outside are dropped. See the Point in Polygon tool for a dedicated point-only workflow.

Multiple Clip Polygons

If the clip layer has multiple polygons, the tool unions them internally so the clip boundary represents the total area covered by all clip features. The output contains every input piece that falls within any clip polygon.

Key Parameters and Options

Input Layer

The layer being clipped. Can be points, lines, polygons, or mixed.

Clip Layer

The layer defining the boundary. Must be polygon geometry. If it contains multiple features, they are effectively treated as a single union.

Preserve Attributes

Default on — output features inherit the input layer's attributes. The clip layer's attributes are not transferred (use GIS Intersect Tool for that).

Practical Applications

Extracting Study Areas

Researchers frequently have a national or global dataset but only need the subset within a specific watershed, national park, or administrative boundary. Clipping to that polygon produces a much lighter dataset for downstream analysis and sharing. A typical workflow: download national OpenStreetMap extracts, clip to a city boundary, and publish.

Urban Planning and Site Analysis

Planners clip zoning, parcels, utilities, floodplains, and slope rasters to a project site boundary to produce a focused due-diligence map package. Clipping before symbolizing avoids drawing millions of features that the audience won't see.

Environmental Impact Assessment

Clip forest cover, wetland inventories, or critical habitat layers to a proposed development footprint to quantify affected acres. Combine with the Area Calculator to produce impact tables for permit applications.

Census and Demographic Work

Clip census blocks, ZIP code tabulation areas, or American Community Survey boundaries to municipal borders to get clean, non-overlapping units for downstream aggregation.

Emergency Management

Clip infrastructure networks to hazard zones (flood inundation, wildfire perimeters, earthquake rupture) to identify exposed assets and prioritize response.

Agriculture

Clip remote-sensing derived vegetation products to field boundaries to compute per-field NDVI averages with the Zonal Statistics tool.

Archaeology

Clip survey transects to permit boundaries to stay within the legally authorized study area.

Step-by-Step Workflow in gis.tools

Open the GIS Clip Tool (Clip Layer by Polygon)
Drag the input layer (points, lines, or polygons) onto the drop zone
Drag the clip layer (polygons only) onto the second drop zone
Preview both layers overlaid on the map
Click "Clip" to compute the intersection
Review the clipped output — feature count should match expectations
Export as GeoJSON, KML, or Shapefile

Worked Example

You are preparing a grant application for wetland restoration in the Chesapeake Bay watershed. You have a national National Wetland Inventory GeoJSON (4 GB), and you need the subset within a single 12-digit HUC sub-watershed polygon. Dragging the HUC polygon into the clip tool as the clip layer and the wetland file as the input layer, you click Clip. After processing, you get a 12,300-feature output file (down from millions) containing only wetlands within the sub-watershed, with all their original ATTRIBUTE_CODE, WETLAND_TYPE, and AREA_ACRES fields intact. You drop the result into the Area Calculator to verify the total wetland area matches the grant eligibility threshold.

Common Pitfalls and Gotchas

CRS mismatch: if the two layers are in different projections, results will be completely wrong. Verify with the CRS Metadata Inspector before clipping.
Invalid clip polygons: self-intersecting rings or unclosed polygons produce empty or partial output. Fix with Geometry Repair.
Empty output: often indicates the layers don't actually overlap in space, or they have different CRS declarations.
Attribute loss: clip keeps only the input layer's attributes. If you need the clip polygon's attributes, switch to GIS Intersect Tool.
Sliver polygons along the boundary: tiny output fragments from floating-point rounding. Filter them by minimum area afterwards.
Line endpoint gaps: clipped lines may end a sub-millimeter short of the clip boundary due to precision issues; rarely important visually.
Performance on very detailed clip polygons: a clip boundary with 100,000 vertices is slow. Simplify the clip with GeoJSON Simplifier if it doesn't need to be that detailed.

Tips for Best Results

Reproject both layers to the same CRS first with the EPSG Reprojector & Coordinate Converter
For raster clipping, use Clip Raster by Polygon instead
Validate the clip polygon with the GeoJSON Validator & Fixer before running
To clip by a bounding box rather than an arbitrary polygon, create a rectangle with the Draw Points/Lines/Polygons tool first
Run a visual preview before exporting large outputs to confirm expected behavior

Comparison with Other GIS Approaches

PostGIS performs clip via SELECT ST_Intersection(a.geom, b.geom) FROM a, b WHERE ST_Intersects(a.geom, b.geom). QGIS exposes it as Vector > Geoprocessing Tools > Clip. ArcGIS Pro offers Clip in the Analysis toolbox, with a newer "pairwise clip" variant optimized for performance. All produce equivalent output; differences are about scale and integration. The browser-based GIS Clip Tool on gis.tools is ideal for interactive analysis, one-off extractions, and privacy-sensitive work. For batch processing of terabytes, a PostGIS or GDAL pipeline is more appropriate.

Performance Considerations

Clip performance scales with input feature count and clip polygon complexity. Thousands of simple points clip in milliseconds. Complex polygon-on-polygon clipping with millions of vertices may exhaust browser memory. Reduce workload by pre-filtering the input with a bounding-box spatial filter, or by running the clip in tiles.

Data Privacy and Browser-Based Processing

All clipping happens in your browser tab. Nothing is uploaded. Your proprietary parcel or client boundary file is read from your local disk, clipped in JavaScript, and saved back to your local disk. Closing the tab clears memory.

Related GIS Concepts

Mask is a raster-context synonym for clip. Extract by Mask is ArcGIS Pro's raster-clip tool. Cookie cutter is informal jargon for the same operation. Clip differs from erase (keep what's outside), intersect (keep overlap with attribute join), and spatial filter (select but don't cut). Clipping is also distinct from cropping a raster to a rectangular extent, which is simpler and faster.

Frequently Asked Questions

What's the difference between clip and intersect?

Clip keeps only the input layer's attributes; intersect carries attributes from both layers forward. Geometrically they produce the same shape.

Can I clip points?

Yes. Points inside the clip polygon survive; points outside are dropped. It's equivalent to a point-in-polygon query.

How do I clip multiple files at once?

Combine them into a single layer first (or run the tool once per file). Batch processing is better suited to GDAL or a QGIS model.

Why does my output have jagged edges along the clip boundary?

The output traces the clip polygon exactly. If the clip polygon was coarsely digitized, the output will follow its coarse edges.

Input Layer (to be clipped)

Clip Layer (boundary polygon)

About Clip