diff --git a/Makefile b/Makefile
index 57c81d1d..d267e077 100644
--- a/Makefile
+++ b/Makefile
@@ -68,16 +68,16 @@ tippecanoe-enumerate: enumerate.o
 tippecanoe-decode: decode.o projection.o mvt.o write_json.o text.o jsonpull/jsonpull.o dirtiles.o pmtiles_file.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3
 
-tile-join: tile-join.o projection.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpull/jsonpull.o text.o evaluator.o csv.o write_json.o pmtiles_file.o clip.o attribute.o thread.o
+tile-join: tile-join.o projection.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpull/jsonpull.o text.o evaluator.o csv.o write_json.o pmtiles_file.o clip.o attribute.o thread.o read_json.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 tippecanoe-json-tool: jsontool.o jsonpull/jsonpull.o csv.o text.o geojson-loop.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
-unit: unit.o text.o sort.o mvt.o projection.o clip.o attribute.o jsonpull/jsonpull.o evaluator.o
+unit: unit.o text.o sort.o mvt.o projection.o clip.o attribute.o jsonpull/jsonpull.o evaluator.o read_json.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
-tippecanoe-overzoom: overzoom.o mvt.o clip.o evaluator.o jsonpull/jsonpull.o text.o attribute.o read_json.o projection.o
+tippecanoe-overzoom: overzoom.o mvt.o clip.o evaluator.o jsonpull/jsonpull.o text.o attribute.o read_json.o projection.o read_json.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 -include $(wildcard *.d)
diff --git a/clip.cpp b/clip.cpp
index e6975a03..7e2a1f3c 100644
--- a/clip.cpp
+++ b/clip.cpp
@@ -13,6 +13,7 @@
 #include "serial.hpp"
 #include "attribute.hpp"
 #include "projection.hpp"
+#include "read_json.hpp"
 
 static std::vector<std::pair<double, double>> clip_poly1(std::vector<std::pair<double, double>> &geom,
 							 long long minx, long long miny, long long maxx, long long maxy,
@@ -1075,6 +1076,42 @@ bool pnpoly_mp(std::vector<mvt_geometry> const &geom, long long x, long long y)
 	return found;
 }
 
+clipbbox parse_clip_poly(std::string arg) {
+	json_pull *jp = json_begin_string(arg.c_str());
+	json_object *j = json_read_tree(jp);
+	if (j->type != JSON_HASH) {
+		fprintf(stderr, "Expected JSON geometry object, not %s\n", arg.c_str());
+	}
+
+	std::pair<int, drawvec> parsed_geometry = parse_geometry(j, jp, j, 0, 0, 0, 1LL << 32, false);
+	json_end(jp);
+
+	clipbbox out;
+	out.minx = LLONG_MAX;
+	out.miny = LLONG_MAX;
+	out.maxx = LLONG_MIN;
+	out.maxy = LLONG_MIN;
+	for (auto const &d : parsed_geometry.second) {
+		if (d.op == VT_MOVETO || d.op == VT_LINETO) {
+			if (d.x < out.minx) {
+				out.minx = d.x;
+			}
+			if (d.y < out.miny) {
+				out.miny = d.y;
+			}
+			if (d.x > out.maxx) {
+				out.maxx = d.x;
+			}
+			if (d.y > out.maxy) {
+				out.maxy = d.y;
+			}
+		}
+	}
+	out.dv = std::move(parsed_geometry.second);
+
+	return out;
+}
+
 std::string overzoom(std::vector<input_tile> const &tiles, int nz, int nx, int ny,
 		     int detail_or_unspecified, int buffer,
 		     std::set<std::string> const &keep,
diff --git a/geometry.hpp b/geometry.hpp
index 2284ab95..45161f3b 100644
--- a/geometry.hpp
+++ b/geometry.hpp
@@ -125,6 +125,8 @@ struct clipbbox {
 	long long miny;
 	long long maxx;
 	long long maxy;
+
+	drawvec dv;  // empty, or arbitrary clipping polygon
 };
 
 std::string overzoom(std::vector<source_tile> const &tiles, int nz, int nx, int ny,
@@ -162,4 +164,6 @@ draw center_of_mass_mp(const drawvec &dv);
 void get_quadkey_bounds(long long xmin, long long ymin, long long xmax, long long ymax,
 			unsigned long long *start, unsigned long long *end);
 
+clipbbox parse_clip_poly(std::string arg);
+
 #endif
diff --git a/overzoom.cpp b/overzoom.cpp
index 514c7669..63822d0f 100644
--- a/overzoom.cpp
+++ b/overzoom.cpp
@@ -72,6 +72,7 @@ int main(int argc, char **argv) {
 		{"numeric-attributes", required_argument, 0, 'a' & 0x1F},
 		{"no-tile-compression", no_argument, 0, 'd' & 0x1F},
 		{"clip-bounding-box", required_argument, 0, 'k' & 0x1F},
+		{"clip-polygon", required_argument, 0, 'l' & 0x1F},
 
 		{0, 0, 0, 0},
 	};
@@ -162,7 +163,7 @@ int main(int argc, char **argv) {
 			do_compress = false;
 			break;
 
-		case 'k' & 0x1F:
+		case 'k' & 0x1F: {
 			clipbbox clip;
 			if (sscanf(optarg, "%lf,%lf,%lf,%lf", &clip.lon1, &clip.lat1, &clip.lon2, &clip.lat2) == 4) {
 				projection->project(clip.lon1, clip.lat1, 32, &clip.minx, &clip.maxy);
@@ -173,6 +174,13 @@ int main(int argc, char **argv) {
 				exit(EXIT_ARGS);
 			}
 			break;
+		}
+
+		case 'l' & 0x1F: {
+			clipbbox clip = parse_clip_poly(optarg);
+			clipbboxes.push_back(clip);
+			break;
+		}
 
 		default:
 			fprintf(stderr, "Unrecognized flag -%c\n", i);
diff --git a/read_json.cpp b/read_json.cpp
index bf5a5e3f..a77fe4be 100644
--- a/read_json.cpp
+++ b/read_json.cpp
@@ -179,7 +179,7 @@ static std::vector<mvt_geometry> to_feature(drawvec &geom) {
 }
 
 std::pair<int, drawvec> parse_geometry(json_object *geometry, json_pull *jp, json_object *j,
-				       int z, int x, int y, int extent, bool fix_longitudes) {
+				       int z, int x, int y, long long extent, bool fix_longitudes) {
 	json_object *geometry_type = json_hash_get(geometry, "type");
 	if (geometry_type == NULL) {
 		fprintf(stderr, "Filter output:%d: null geometry (additional not reported): ", jp->line);
diff --git a/read_json.hpp b/read_json.hpp
index 84e0853b..6323c497 100644
--- a/read_json.hpp
+++ b/read_json.hpp
@@ -12,6 +12,8 @@ extern int mb_geometry[GEOM_TYPES];
 
 void json_context(json_object *j);
 void parse_coordinates(int t, json_object *j, drawvec &out, int op, const char *fname, int line, json_object *feature);
+std::pair<int, drawvec> parse_geometry(json_object *geometry, json_pull *jp, json_object *j,
+				       int z, int x, int y, long long extent, bool fix_longitudes);
 std::vector<mvt_layer> parse_layers(FILE *fp, int z, unsigned x, unsigned y, int extent, bool fix_longitudes);
 
 serial_val stringify_value(json_object *value, const char *reading, int line, json_object *feature);