diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index bd8f465..517ca8b 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -42,3 +42,16 @@ jobs:
           wget -q https://github.com/postgres/postgres/archive/refs/tags/REL_14_5.tar.gz
           tar xf REL_14_5.tar.gz
           make prove_installcheck PROVE=prove PROVE_FLAGS="-I ./postgres-REL_14_5/src/test/perl" PERL5LIB="/Users/runner/perl5/lib/perl5"
+  windows:
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ankane/setup-postgres@v1
+        with:
+          postgres-version: 14
+      - run: |
+          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvars64.bat"
+          nmake /NOLOGO /F Makefile.win
+          nmake /NOLOGO /F Makefile.win install
+          nmake /NOLOGO /F Makefile.win installcheck
+        shell: cmd
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f7fb786..e444b74 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 - Changed text representation for vector elements to match `real`
 - Improved accuracy of text parsing for certain inputs
+- Added experimental support for Windows
 
 ## 0.3.2 (2022-11-22)
 
diff --git a/Makefile.win b/Makefile.win
new file mode 100644
index 0000000..eb4b1d4
--- /dev/null
+++ b/Makefile.win
@@ -0,0 +1,65 @@
+EXTENSION = vector
+EXTVERSION = 0.3.2
+
+OBJS = src\ivfbuild.obj src\ivfflat.obj src\ivfinsert.obj src\ivfkmeans.obj src\ivfscan.obj src\ivfutils.obj src\ivfvacuum.obj src\vector.obj
+
+# For /arch flags
+# https://learn.microsoft.com/en-us/cpp/build/reference/arch-minimum-cpu-architecture
+OPTFLAGS =
+
+# For auto-vectorization:
+# - MSVC (needs /O2 /fp:fast) - https://learn.microsoft.com/en-us/cpp/parallel/auto-parallelization-and-auto-vectorization?#auto-vectorizer
+PG_CFLAGS = $(PG_CFLAGS) $(OPTFLAGS) /O2 /fp:fast
+
+# Debug MSVC auto-vectorization
+# https://learn.microsoft.com/en-us/cpp/error-messages/tool-errors/vectorizer-and-parallelizer-messages
+# PG_CFLAGS = $(PG_CFLAGS) /Qvec-report:2
+
+all: sql\$(EXTENSION)--$(EXTVERSION).sql
+
+sql\$(EXTENSION)--$(EXTVERSION).sql: sql\$(EXTENSION).sql
+	copy sql\$(EXTENSION).sql $@
+
+# TODO use pg_config
+INCLUDEDIR = $(PGROOT)\include
+INCLUDEDIR_SERVER = $(PGROOT)\include\server
+LIBDIR = $(PGROOT)\lib
+PKGLIBDIR = $(PGROOT)\lib
+SHAREDIR = $(PGROOT)\share
+
+CFLAGS = /nologo /I"$(INCLUDEDIR_SERVER)\port\win32_msvc" /I"$(INCLUDEDIR_SERVER)\port\win32" /I"$(INCLUDEDIR_SERVER)" /I"$(INCLUDEDIR)"
+
+CFLAGS = $(CFLAGS) $(PG_CFLAGS)
+
+SHLIB = src\$(EXTENSION).dll
+
+LIBS = "$(LIBDIR)\postgres.lib"
+
+.c.obj:
+	$(CC) $(CFLAGS) /c $< /Fo$@
+
+$(SHLIB): $(OBJS)
+	$(CC) $(CFLAGS) $(OBJS) $(LIBS) /link /DLL /OUT:$(SHLIB)
+
+all: $(SHLIB)
+
+install:
+	copy $(SHLIB) "$(PKGLIBDIR)"
+	copy $(EXTENSION).control "$(SHAREDIR)\extension"
+	copy sql\$(EXTENSION)--*.sql "$(SHAREDIR)\extension"
+
+# TODO improve
+installcheck:
+	createdb contrib_regression
+	mkdir -p results
+	psql -d contrib_regression -a -q -f test\sql\btree.sql > results\btree.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\cast.sql > results\cast.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\copy.sql > results\copy.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\functions.sql > results\functions.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\input.sql > results\input.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\ivfflat_cosine.sql > results\ivfflat_cosine.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\ivfflat_ip.sql > results\ivfflat_ip.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\ivfflat_l2.sql > results\ivfflat_l2.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\ivfflat_options.sql > results\ivfflat_options.out 2>&1
+	psql -d contrib_regression -a -q -f test\sql\ivfflat_unlogged.sql > results\ivfflat_unlogged.out 2>&1
+	cat results/*
diff --git a/src/ivfflat.c b/src/ivfflat.c
index 35c0e48..0829458 100644
--- a/src/ivfflat.c
+++ b/src/ivfflat.c
@@ -164,7 +164,7 @@ ivfflatvalidate(Oid opclassoid)
  *
  * See https://www.postgresql.org/docs/current/index-api.html
  */
-PG_FUNCTION_INFO_V1(ivfflathandler);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(ivfflathandler);
 Datum
 ivfflathandler(PG_FUNCTION_ARGS)
 {
diff --git a/src/ivfflat.h b/src/ivfflat.h
index 13c3425..0aafe20 100644
--- a/src/ivfflat.h
+++ b/src/ivfflat.h
@@ -78,6 +78,9 @@
 /* Variables */
 extern int	ivfflat_probes;
 
+/* Exported functions */
+PGDLLEXPORT void _PG_init(void);
+
 typedef struct VectorArrayData
 {
 	int			length;
@@ -210,7 +213,6 @@ typedef IvfflatScanOpaqueData * IvfflatScanOpaque;
 #define VectorArraySet(_arr, _offset, _val) (memcpy(VECTOR_ARRAY_OFFSET(_arr, _offset), _val, VECTOR_SIZE(_arr->dim)))
 
 /* Methods */
-void		_PG_init(void);
 VectorArray VectorArrayInit(int maxlen, int dimensions);
 void		VectorArrayFree(VectorArray arr);
 void		PrintVectorArray(char *msg, VectorArray arr);
diff --git a/src/vector.c b/src/vector.c
index 2661282..22a9853 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -109,7 +109,7 @@ PrintVector(char *msg, Vector * vector)
 /*
  * Convert textual representation to internal representation
  */
-PG_FUNCTION_INFO_V1(vector_in);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_in);
 Datum
 vector_in(PG_FUNCTION_ARGS)
 {
@@ -186,7 +186,7 @@ vector_in(PG_FUNCTION_ARGS)
 /*
  * Convert internal representation to textual representation
  */
-PG_FUNCTION_INFO_V1(vector_out);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_out);
 Datum
 vector_out(PG_FUNCTION_ARGS)
 {
@@ -247,7 +247,7 @@ vector_out(PG_FUNCTION_ARGS)
 /*
  * Convert type modifier
  */
-PG_FUNCTION_INFO_V1(vector_typmod_in);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_typmod_in);
 Datum
 vector_typmod_in(PG_FUNCTION_ARGS)
 {
@@ -278,7 +278,7 @@ vector_typmod_in(PG_FUNCTION_ARGS)
 /*
  * Convert external binary representation to internal representation
  */
-PG_FUNCTION_INFO_V1(vector_recv);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_recv);
 Datum
 vector_recv(PG_FUNCTION_ARGS)
 {
@@ -310,7 +310,7 @@ vector_recv(PG_FUNCTION_ARGS)
 /*
  * Convert internal representation to the external binary representation
  */
-PG_FUNCTION_INFO_V1(vector_send);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_send);
 Datum
 vector_send(PG_FUNCTION_ARGS)
 {
@@ -330,7 +330,7 @@ vector_send(PG_FUNCTION_ARGS)
 /*
  * Convert vector to vector
  */
-PG_FUNCTION_INFO_V1(vector);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector);
 Datum
 vector(PG_FUNCTION_ARGS)
 {
@@ -345,7 +345,7 @@ vector(PG_FUNCTION_ARGS)
 /*
  * Convert array to vector
  */
-PG_FUNCTION_INFO_V1(array_to_vector);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(array_to_vector);
 Datum
 array_to_vector(PG_FUNCTION_ARGS)
 {
@@ -403,7 +403,7 @@ array_to_vector(PG_FUNCTION_ARGS)
 /*
  * Convert vector to float4[]
  */
-PG_FUNCTION_INFO_V1(vector_to_float4);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_to_float4);
 Datum
 vector_to_float4(PG_FUNCTION_ARGS)
 {
@@ -426,12 +426,14 @@ vector_to_float4(PG_FUNCTION_ARGS)
 /*
  * Get the L2 distance between vectors
  */
-PG_FUNCTION_INFO_V1(l2_distance);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(l2_distance);
 Datum
 l2_distance(PG_FUNCTION_ARGS)
 {
 	Vector	   *a = PG_GETARG_VECTOR_P(0);
 	Vector	   *b = PG_GETARG_VECTOR_P(1);
+	float	   *ax = a->x;
+	float	   *bx = b->x;
 	double		distance = 0.0;
 	double		diff;
 
@@ -439,7 +441,7 @@ l2_distance(PG_FUNCTION_ARGS)
 
 	for (int i = 0; i < a->dim; i++)
 	{
-		diff = a->x[i] - b->x[i];
+		diff = ax[i] - bx[i];
 		distance += diff * diff;
 	}
 
@@ -450,12 +452,14 @@ l2_distance(PG_FUNCTION_ARGS)
  * Get the L2 squared distance between vectors
  * This saves a sqrt calculation
  */
-PG_FUNCTION_INFO_V1(vector_l2_squared_distance);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_l2_squared_distance);
 Datum
 vector_l2_squared_distance(PG_FUNCTION_ARGS)
 {
 	Vector	   *a = PG_GETARG_VECTOR_P(0);
 	Vector	   *b = PG_GETARG_VECTOR_P(1);
+	float	   *ax = a->x;
+	float	   *bx = b->x;
 	double		distance = 0.0;
 	double		diff;
 
@@ -463,7 +467,7 @@ vector_l2_squared_distance(PG_FUNCTION_ARGS)
 
 	for (int i = 0; i < a->dim; i++)
 	{
-		diff = a->x[i] - b->x[i];
+		diff = ax[i] - bx[i];
 		distance += diff * diff;
 	}
 
@@ -473,18 +477,20 @@ vector_l2_squared_distance(PG_FUNCTION_ARGS)
 /*
  * Get the inner product of two vectors
  */
-PG_FUNCTION_INFO_V1(inner_product);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(inner_product);
 Datum
 inner_product(PG_FUNCTION_ARGS)
 {
 	Vector	   *a = PG_GETARG_VECTOR_P(0);
 	Vector	   *b = PG_GETARG_VECTOR_P(1);
+	float	   *ax = a->x;
+	float	   *bx = b->x;
 	double		distance = 0.0;
 
 	CheckDims(a, b);
 
 	for (int i = 0; i < a->dim; i++)
-		distance += a->x[i] * b->x[i];
+		distance += ax[i] * bx[i];
 
 	PG_RETURN_FLOAT8(distance);
 }
@@ -492,18 +498,20 @@ inner_product(PG_FUNCTION_ARGS)
 /*
  * Get the negative inner product of two vectors
  */
-PG_FUNCTION_INFO_V1(vector_negative_inner_product);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_negative_inner_product);
 Datum
 vector_negative_inner_product(PG_FUNCTION_ARGS)
 {
 	Vector	   *a = PG_GETARG_VECTOR_P(0);
 	Vector	   *b = PG_GETARG_VECTOR_P(1);
+	float	   *ax = a->x;
+	float	   *bx = b->x;
 	double		distance = 0.0;
 
 	CheckDims(a, b);
 
 	for (int i = 0; i < a->dim; i++)
-		distance += a->x[i] * b->x[i];
+		distance += ax[i] * bx[i];
 
 	PG_RETURN_FLOAT8(distance * -1);
 }
@@ -511,12 +519,14 @@ vector_negative_inner_product(PG_FUNCTION_ARGS)
 /*
  * Get the cosine distance between two vectors
  */
-PG_FUNCTION_INFO_V1(cosine_distance);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(cosine_distance);
 Datum
 cosine_distance(PG_FUNCTION_ARGS)
 {
 	Vector	   *a = PG_GETARG_VECTOR_P(0);
 	Vector	   *b = PG_GETARG_VECTOR_P(1);
+	float	   *ax = a->x;
+	float	   *bx = b->x;
 	double		distance = 0.0;
 	double		norma = 0.0;
 	double		normb = 0.0;
@@ -525,9 +535,9 @@ cosine_distance(PG_FUNCTION_ARGS)
 
 	for (int i = 0; i < a->dim; i++)
 	{
-		distance += a->x[i] * b->x[i];
-		norma += a->x[i] * a->x[i];
-		normb += b->x[i] * b->x[i];
+		distance += ax[i] * bx[i];
+		norma += ax[i] * ax[i];
+		normb += bx[i] * bx[i];
 	}
 
 	PG_RETURN_FLOAT8(1 - (distance / (sqrt(norma) * sqrt(normb))));
@@ -538,7 +548,7 @@ cosine_distance(PG_FUNCTION_ARGS)
  * Currently uses angular distance since needs to satisfy triangle inequality
  * Assumes inputs are unit vectors (skips norm)
  */
-PG_FUNCTION_INFO_V1(vector_spherical_distance);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_spherical_distance);
 Datum
 vector_spherical_distance(PG_FUNCTION_ARGS)
 {
@@ -563,7 +573,7 @@ vector_spherical_distance(PG_FUNCTION_ARGS)
 /*
  * Get the dimensions of a vector
  */
-PG_FUNCTION_INFO_V1(vector_dims);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_dims);
 Datum
 vector_dims(PG_FUNCTION_ARGS)
 {
@@ -575,15 +585,16 @@ vector_dims(PG_FUNCTION_ARGS)
 /*
  * Get the L2 norm of a vector
  */
-PG_FUNCTION_INFO_V1(vector_norm);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_norm);
 Datum
 vector_norm(PG_FUNCTION_ARGS)
 {
 	Vector	   *a = PG_GETARG_VECTOR_P(0);
+	float	   *ax = a->x;
 	double		norm = 0.0;
 
 	for (int i = 0; i < a->dim; i++)
-		norm += a->x[i] * a->x[i];
+		norm += ax[i] * ax[i];
 
 	PG_RETURN_FLOAT8(sqrt(norm));
 }
@@ -591,20 +602,23 @@ vector_norm(PG_FUNCTION_ARGS)
 /*
  * Add vectors
  */
-PG_FUNCTION_INFO_V1(vector_add);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_add);
 Datum
 vector_add(PG_FUNCTION_ARGS)
 {
 	Vector	   *a = PG_GETARG_VECTOR_P(0);
 	Vector	   *b = PG_GETARG_VECTOR_P(1);
+	float	   *ax = a->x;
+	float	   *bx = b->x;
 	Vector	   *result;
-	int			i;
+	float	   *rx;
 
 	CheckDims(a, b);
 
 	result = InitVector(a->dim);
-	for (i = 0; i < a->dim; i++)
-		result->x[i] = a->x[i] + b->x[i];
+	rx = result->x;
+	for (int i = 0, imax = a->dim; i < imax; i++)
+		rx[i] = ax[i] + bx[i];
 
 	PG_RETURN_POINTER(result);
 }
@@ -612,20 +626,23 @@ vector_add(PG_FUNCTION_ARGS)
 /*
  * Subtract vectors
  */
-PG_FUNCTION_INFO_V1(vector_sub);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_sub);
 Datum
 vector_sub(PG_FUNCTION_ARGS)
 {
 	Vector	   *a = PG_GETARG_VECTOR_P(0);
 	Vector	   *b = PG_GETARG_VECTOR_P(1);
+	float	   *ax = a->x;
+	float	   *bx = b->x;
 	Vector	   *result;
-	int			i;
+	float	   *rx;
 
 	CheckDims(a, b);
 
 	result = InitVector(a->dim);
-	for (i = 0; i < a->dim; i++)
-		result->x[i] = a->x[i] - b->x[i];
+	rx = result->x;
+	for (int i = 0, imax = a->dim; i < imax; i++)
+		rx[i] = ax[i] - bx[i];
 
 	PG_RETURN_POINTER(result);
 }
@@ -654,7 +671,7 @@ vector_cmp_internal(Vector * a, Vector * b)
 /*
  * Less than
  */
-PG_FUNCTION_INFO_V1(vector_lt);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_lt);
 Datum
 vector_lt(PG_FUNCTION_ARGS)
 {
@@ -667,7 +684,7 @@ vector_lt(PG_FUNCTION_ARGS)
 /*
  * Less than or equal
  */
-PG_FUNCTION_INFO_V1(vector_le);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_le);
 Datum
 vector_le(PG_FUNCTION_ARGS)
 {
@@ -680,7 +697,7 @@ vector_le(PG_FUNCTION_ARGS)
 /*
  * Equal
  */
-PG_FUNCTION_INFO_V1(vector_eq);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_eq);
 Datum
 vector_eq(PG_FUNCTION_ARGS)
 {
@@ -693,7 +710,7 @@ vector_eq(PG_FUNCTION_ARGS)
 /*
  * Not equal
  */
-PG_FUNCTION_INFO_V1(vector_ne);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_ne);
 Datum
 vector_ne(PG_FUNCTION_ARGS)
 {
@@ -706,7 +723,7 @@ vector_ne(PG_FUNCTION_ARGS)
 /*
  * Greater than or equal
  */
-PG_FUNCTION_INFO_V1(vector_ge);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_ge);
 Datum
 vector_ge(PG_FUNCTION_ARGS)
 {
@@ -719,7 +736,7 @@ vector_ge(PG_FUNCTION_ARGS)
 /*
  * Greater than
  */
-PG_FUNCTION_INFO_V1(vector_gt);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_gt);
 Datum
 vector_gt(PG_FUNCTION_ARGS)
 {
@@ -732,7 +749,7 @@ vector_gt(PG_FUNCTION_ARGS)
 /*
  * Compare vectors
  */
-PG_FUNCTION_INFO_V1(vector_cmp);
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_cmp);
 Datum
 vector_cmp(PG_FUNCTION_ARGS)
 {