diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7fb92f0..89d910d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,15 @@ on:
 
 jobs:
   build-and-test:
-    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+        include:
+          - os: ubuntu-latest
+            artifact: libzimalloc.so
+          - os: windows-latest
+            artifact: zimalloc.*
+    runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -24,6 +32,7 @@ jobs:
            version: master
 
       - name: Check formatting
+        if: runner.os == 'Linux'
         run: zig fmt --check .
 
       - name: Run tests
@@ -41,7 +50,7 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           name: libzimalloc
-          path: zig-out-*/lib/libzimalloc.so
+          path: zig-out-*/lib/${{ matrix.artifact }}
 
   mimalloc-bench-smoke-test:
     runs-on: ubuntu-latest
diff --git a/build.zig b/build.zig
index b9bf165..58653ca 100644
--- a/build.zig
+++ b/build.zig
@@ -85,6 +85,9 @@ pub fn build(b: *std.Build) void {
         .link_libc = true,
     });
     tests.root_module.addImport("build_options", zimalloc_options);
+    if (target.result.os.tag == .windows) {
+        tests.linkSystemLibrary("onecore.lib");
+    }
 
     const tests_run = b.addRunArtifact(tests);
 
diff --git a/src/Page.zig b/src/Page.zig
index ca7267d..d2275ae 100644
--- a/src/Page.zig
+++ b/src/Page.zig
@@ -60,7 +60,17 @@ pub fn deinit(self: *Page) !void {
     segment.init_set.unset(page_index);
 
     const page_bytes = segment.pageSlice(page_index);
-    try std.os.madvise(page_bytes.ptr, page_bytes.len, std.os.MADV.DONTNEED);
+    switch (@import("builtin").os.tag) {
+        .linux => try std.posix.madvise(page_bytes.ptr, page_bytes.len, std.posix.MADV.DONTNEED),
+        // TODO: test this windows impl, presumably it's broken
+        .windows => _ = try std.os.windows.VirtualAlloc(
+            page_bytes.ptr,
+            page_bytes.len,
+            std.os.windows.MEM_RESET,
+            std.os.windows.PAGE_NOACCESS,
+        ),
+        else => |tag| @compileError(@tagName(tag) ++ " is not supported yet"),
+    }
 }
 
 pub fn getPtrInFreeSlot(self: *const Page) *align(constants.min_slot_alignment) anyopaque {
diff --git a/src/huge_alignment.zig b/src/huge_alignment.zig
index a8fecfc..7bc195f 100644
--- a/src/huge_alignment.zig
+++ b/src/huge_alignment.zig
@@ -1,66 +1,7 @@
-/// The `size` is  rounded up to a multiple of `std.mem.page_size`.
-/// Can be freed with std.os.unmap
-pub fn allocateOptions(
-    size: usize,
-    alignment: usize,
-    prot: u32,
-    flags: std.os.MAP,
-) ?[]align(std.mem.page_size) u8 {
-    assert.withMessage(@src(), alignment > std.mem.page_size, "alignment is not greater than the page size");
-    assert.withMessage(@src(), std.mem.isValidAlign(alignment), "alignment is not a power of two");
+const builtin = @import("builtin");
 
-    const mmap_length = size + alignment - 1;
-    const unaligned = std.os.mmap(null, mmap_length, prot, flags, -1, 0) catch return null;
-    const unaligned_address = @intFromPtr(unaligned.ptr);
-    const aligned_address = std.mem.alignForward(usize, unaligned_address, alignment);
-
-    const aligned_size = std.mem.alignForward(usize, size, std.mem.page_size);
-
-    if (aligned_address == unaligned_address) {
-        std.os.munmap(@alignCast(unaligned[aligned_size..]));
-        return unaligned[0..aligned_size];
-    } else {
-        const offset = aligned_address - unaligned_address;
-        assert.withMessage(@src(), std.mem.isAligned(offset, std.mem.page_size), "offset is not aligned");
-
-        std.os.munmap(unaligned[0..offset]);
-        std.os.munmap(@alignCast(unaligned[offset + aligned_size ..]));
-        return @alignCast(unaligned[offset..][0..aligned_size]);
-    }
-}
-
-/// Makes a readable, writeable, anonymous private mapping with size rounded up to
-/// a multiple of `std.mem.page_size`. Should be freed with `deallocate()`.
-pub fn allocate(size: usize, alignment: usize) ?[]align(std.mem.page_size) u8 {
-    return allocateOptions(
-        size,
-        alignment,
-        std.os.PROT.READ | std.os.PROT.WRITE,
-        .{ .TYPE = .PRIVATE, .ANONYMOUS = true },
-    );
-}
-
-/// Rounds `buf.len` up to a multiple of `std.mem.page_size`.
-pub fn deallocate(buf: []align(std.mem.page_size) const u8) void {
-    const aligned_len = std.mem.alignForward(usize, buf.len, std.mem.page_size);
-    std.os.munmap(buf.ptr[0..aligned_len]);
-}
-
-pub fn resizeAllocation(buf: []align(std.mem.page_size) u8, new_len: usize) bool {
-    const old_aligned_len = std.mem.alignForward(usize, buf.len, std.mem.page_size);
-    const new_aligned_len = std.mem.alignForward(usize, new_len, std.mem.page_size);
-
-    if (new_aligned_len == old_aligned_len) {
-        return true;
-    } else if (new_aligned_len < old_aligned_len) {
-        const trailing_ptr: [*]align(std.mem.page_size) u8 = @alignCast(buf.ptr + new_aligned_len);
-        std.os.munmap(trailing_ptr[0 .. old_aligned_len - new_aligned_len]);
-        return true;
-    } else {
-        return false;
-    }
-}
-
-const std = @import("std");
-
-const assert = @import("assert.zig");
+pub usingnamespace switch (builtin.os.tag) {
+    .linux => @import("huge_alignment/linux.zig"),
+    .windows => @import("huge_alignment/windows.zig"),
+    else => |tag| @compileError(@tagName(tag) ++ "is not supported yet"),
+};
diff --git a/src/huge_alignment/linux.zig b/src/huge_alignment/linux.zig
new file mode 100644
index 0000000..3c0ec33
--- /dev/null
+++ b/src/huge_alignment/linux.zig
@@ -0,0 +1,66 @@
+/// The `size` is rounded up to a multiple of `std.mem.page_size`.
+/// Can be freed with std.os.unmap
+fn allocateOptions(
+    size: usize,
+    alignment: usize,
+    prot: u32,
+    flags: std.posix.MAP,
+) ?[]align(std.mem.page_size) u8 {
+    assert.withMessage(@src(), alignment > std.mem.page_size, "alignment is not greater than the page size");
+    assert.withMessage(@src(), std.mem.isValidAlign(alignment), "alignment is not a power of two");
+
+    const mmap_length = size + alignment - 1;
+    const unaligned = std.posix.mmap(null, mmap_length, prot, flags, -1, 0) catch return null;
+    const unaligned_address = @intFromPtr(unaligned.ptr);
+    const aligned_address = std.mem.alignForward(usize, unaligned_address, alignment);
+
+    const aligned_size = std.mem.alignForward(usize, size, std.mem.page_size);
+
+    if (aligned_address == unaligned_address) {
+        std.posix.munmap(@alignCast(unaligned[aligned_size..]));
+        return unaligned[0..aligned_size];
+    } else {
+        const offset = aligned_address - unaligned_address;
+        assert.withMessage(@src(), std.mem.isAligned(offset, std.mem.page_size), "offset is not aligned");
+
+        std.posix.munmap(unaligned[0..offset]);
+        std.posix.munmap(@alignCast(unaligned[offset + aligned_size ..]));
+        return @alignCast(unaligned[offset..][0..aligned_size]);
+    }
+}
+
+/// Makes a readable, writeable, anonymous private mapping with size rounded up to
+/// a multiple of `std.mem.page_size`. Should be freed with `deallocate()`.
+pub fn allocate(size: usize, alignment: usize) ?[]align(std.mem.page_size) u8 {
+    return allocateOptions(
+        size,
+        alignment,
+        std.posix.PROT.READ | std.posix.PROT.WRITE,
+        .{ .TYPE = .PRIVATE, .ANONYMOUS = true },
+    );
+}
+
+/// Rounds `buf.len` up to a multiple of `std.mem.page_size`.
+pub fn deallocate(buf: []align(std.mem.page_size) const u8) void {
+    const aligned_len = std.mem.alignForward(usize, buf.len, std.mem.page_size);
+    std.posix.munmap(buf.ptr[0..aligned_len]);
+}
+
+pub fn resizeAllocation(buf: []align(std.mem.page_size) u8, new_len: usize) bool {
+    const old_aligned_len = std.mem.alignForward(usize, buf.len, std.mem.page_size);
+    const new_aligned_len = std.mem.alignForward(usize, new_len, std.mem.page_size);
+
+    if (new_aligned_len == old_aligned_len) {
+        return true;
+    } else if (new_aligned_len < old_aligned_len) {
+        const trailing_ptr: [*]align(std.mem.page_size) u8 = @alignCast(buf.ptr + new_aligned_len);
+        std.posix.munmap(trailing_ptr[0 .. old_aligned_len - new_aligned_len]);
+        return true;
+    } else {
+        return false;
+    }
+}
+
+const std = @import("std");
+
+const assert = @import("../assert.zig");
diff --git a/src/huge_alignment/windows.zig b/src/huge_alignment/windows.zig
new file mode 100644
index 0000000..4874aec
--- /dev/null
+++ b/src/huge_alignment/windows.zig
@@ -0,0 +1,142 @@
+/// Makes a readable, writeable, anonymous private mapping with size rounded up to
+/// a multiple of `std.mem.page_size`. Should be freed with `deallocate()`.
+pub fn allocate(size: usize, alignment: usize) ?[]align(std.mem.page_size) u8 {
+    return allocateOptions(
+        size,
+        alignment,
+        windows.PAGE_READWRITE,
+        windows.MEM_COMMIT | windows.MEM_RESERVE,
+    );
+}
+
+/// Rounds `buf.len` up to a multiple of `std.mem.page_size`.
+pub fn deallocate(buf: []align(std.mem.page_size) u8) void {
+    windows.VirtualFree(@ptrCast(buf.ptr), 0, windows.MEM_RELEASE);
+}
+
+pub fn resizeAllocation(buf: []align(std.mem.page_size) u8, new_len: usize) bool {
+    const old_aligned_len = std.mem.alignForward(usize, buf.len, std.mem.page_size);
+    const new_aligned_len = std.mem.alignForward(usize, new_len, std.mem.page_size);
+
+    if (new_aligned_len == old_aligned_len) {
+        return true;
+    } else if (new_aligned_len < old_aligned_len) {
+        const trailing_ptr: [*]align(std.mem.page_size) u8 = @alignCast(buf.ptr + new_aligned_len);
+        windows.VirtualFree(trailing_ptr, old_aligned_len - new_aligned_len, windows.MEM_DECOMMIT);
+        return true;
+    } else {
+        return false;
+    }
+}
+
+const kernel32 = struct {
+    extern "kernel32" fn VirtualAlloc2(Process: ?HANDLE, BaseAddress: ?PVOID, Size: SIZE_T, AllocationType: ULONG, PageProtection: ULONG, ExtendedParameters: [*]MEM_EXTENDED_PARAMETER, ParameterCount: ULONG) callconv(WINAPI) ?PVOID;
+};
+
+pub const VirtualAlloc2Error = error{Unexpected};
+
+fn VirtualAlloc2(
+    process: ?HANDLE,
+    base_address: ?PVOID,
+    size: SIZE_T,
+    allocation_type: ULONG,
+    prot: ULONG,
+    extended_parameters: []MEM_EXTENDED_PARAMETER,
+) VirtualAlloc2Error!PVOID {
+    return kernel32.VirtualAlloc2(
+        process,
+        base_address,
+        size,
+        allocation_type,
+        prot,
+        extended_parameters.ptr,
+        @intCast(extended_parameters.len),
+    ) orelse {
+        switch (windows.kernel32.GetLastError()) {
+            // TODO: handle errors that can happen
+            else => |err| return windows.unexpectedError(err),
+        }
+    };
+}
+
+fn allocateOptions(
+    size: usize,
+    alignment: usize,
+    prot: ULONG,
+    alloc_type: ULONG,
+) ?[]align(std.mem.page_size) u8 {
+    assert.withMessage(@src(), alignment > std.mem.page_size, "alignment is not greater than the page size");
+    assert.withMessage(@src(), std.mem.isValidAlign(alignment), "alignment is not a power of two");
+
+    var mem_address_requirements = _MEM_ADDRESS_REQUIREMENTS{
+        .lowest_address = null,
+        .highest_address = null,
+        .alignment = alignment,
+    };
+
+    var extended_parameters = [_]MEM_EXTENDED_PARAMETER{
+        .{
+            .dummy = .{ .Type = .address_requirements },
+            .param = .{ .Pointer = &mem_address_requirements },
+        },
+    };
+
+    const aligned_size = std.mem.alignForward(usize, size, std.mem.page_size);
+    const ptr = VirtualAlloc2(null, null, aligned_size, alloc_type, prot, &extended_parameters) catch
+        return null;
+    return @alignCast(@as([*]u8, @ptrCast(ptr))[0..aligned_size]);
+}
+
+// TODO: figure out how to deallocate - problem is that VirtualFree with MEM_RELEASE requires
+// the originally returned base pointer which does not play well with forcing alignment greater
+// than VirtualAlloc guarantees
+
+const std = @import("std");
+
+const windows = std.os.windows;
+
+const DWORD64 = windows.DWORD64;
+const DWORD = windows.DWORD;
+const SIZE_T = windows.SIZE_T;
+const HANDLE = windows.HANDLE;
+const PVOID = windows.PVOID;
+const ULONG = windows.ULONG;
+const WINAPI = windows.WINAPI;
+
+const MEM_EXTENDED_PARAMETER_BITS = 8;
+const MEM_EXTENDED_PARAMETER = extern struct {
+    dummy: packed struct(u64) {
+        Type: MEM_EXTENDED_PARAMETER_TYPE,
+        RESERVED: std.meta.Int(.unsigned, 64 - MEM_EXTENDED_PARAMETER_BITS) = 0,
+    },
+    param: extern union {
+        ULong64: DWORD64,
+        Pointer: PVOID,
+        Size: SIZE_T,
+        Handle: HANDLE,
+        ULong: DWORD,
+    },
+};
+
+const MEM_EXTENDED_PARAMETER_TYPE = enum(std.meta.Int(.unsigned, MEM_EXTENDED_PARAMETER_BITS)) {
+    invalid,
+    address_requirements,
+    numa_node,
+    partition_handle,
+    user_physical_handle,
+    attribute_flags,
+    image_machine,
+    max,
+};
+
+const _MEM_ADDRESS_REQUIREMENTS = extern struct {
+    lowest_address: ?PVOID,
+    highest_address: ?PVOID,
+    alignment: SIZE_T,
+};
+
+const assert = @import("../assert.zig");
+
+comptime {
+    _ = std.testing.refAllDecls(@This());
+}
diff --git a/src/libzimalloc.zig b/src/libzimalloc.zig
index d109098..aa13965 100644
--- a/src/libzimalloc.zig
+++ b/src/libzimalloc.zig
@@ -75,7 +75,7 @@ export fn posix_memalign(ptr: *?*anyopaque, alignment: usize, size: usize) c_int
     }
 
     if (@popCount(alignment) != 1 or alignment < @sizeOf(*anyopaque)) {
-        return @intFromEnum(std.os.E.INVAL);
+        return @intFromEnum(std.posix.E.INVAL);
     }
 
     if (allocateBytes(size, alignment, @returnAddress(), false, false, false)) |p| {
@@ -83,7 +83,7 @@ export fn posix_memalign(ptr: *?*anyopaque, alignment: usize, size: usize) c_int
         return 0;
     }
 
-    return @intFromEnum(std.os.E.NOMEM);
+    return @intFromEnum(std.posix.E.NOMEM);
 }
 
 export fn memalign(alignment: usize, size: usize) ?*anyopaque {