diff --git a/build.zig b/build.zig
index a321dd31c22a33e939e18455216edd06a5f3ea24..c1e71ffa5c4dfd097f456120fb0f0d7f4be84be7 100644
--- a/build.zig
+++ b/build.zig
@@ -2,7 +2,7 @@ const std = @import("std");
 
 pub fn build(b: *std.Build) void {
     const target = b.standardTargetOptions(.{});
-    const mode = b.option(std.builtin.Mode, "mode", "") orelse .Debug;
+    const mode = b.option(std.builtin.OptimizeMode, "mode", "") orelse .Debug;
     const disable_llvm = b.option(bool, "disable_llvm", "use the non-llvm zig codegen") orelse false;
 
     const mod = b.addModule("extras", .{
@@ -10,9 +10,11 @@ pub fn build(b: *std.Build) void {
     });
 
     const tests = b.addTest(.{
-        .root_source_file = b.path("src/lib.zig"),
-        .target = target,
-        .optimize = mode,
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("src/lib.zig"),
+            .target = target,
+            .optimize = mode,
+        }),
     });
     tests.root_module.addImport("extras", mod);
     tests.use_llvm = !disable_llvm;
diff --git a/src/FixedMaxBuffer.zig b/src/FixedMaxBuffer.zig
index 7fe9f4878f09438c015a130fd77bc5a0007e2913..210b6c7d16de3ababce2b5dacb8f7e622a2a8a12 100644
--- a/src/FixedMaxBuffer.zig
+++ b/src/FixedMaxBuffer.zig
@@ -10,7 +10,7 @@ pub fn FixedMaxBuffer(comptime max_len: usize) type {
         pos: usize,
 
         const Self = @This();
-        pub const Reader = std.io.Reader(*Self, error{}, read);
+        pub const Reader = std.io.GenericReader(*Self, error{}, read);
 
         pub fn init(r: anytype, runtime_len: usize) !Self {
             var fmr = Self{
diff --git a/src/fmtByteCountIEC.zig b/src/fmtByteCountIEC.zig
index fa494cc8df5553af88d71f6994d50dc6abe5c769..97a6b574c549099cf0810e64224a71150d37274d 100644
--- a/src/fmtByteCountIEC.zig
+++ b/src/fmtByteCountIEC.zig
@@ -12,14 +12,14 @@ fn formatByteCountIEC(bytes: u64, writer: *std.Io.Writer) !void {
 }
 
 test {
-    try std.testing.expectFmt("1 B", "{}", .{fmtByteCountIEC(std.math.pow(u64, 1024, 0))});
+    try std.testing.expectFmt("1 B", "{f}", .{fmtByteCountIEC(std.math.pow(u64, 1024, 0))});
 }
 test {
-    try std.testing.expectFmt("1.000 KB", "{}", .{fmtByteCountIEC(std.math.pow(u64, 1024, 1))});
+    try std.testing.expectFmt("1.000 KB", "{f}", .{fmtByteCountIEC(std.math.pow(u64, 1024, 1))});
 }
 test {
-    try std.testing.expectFmt("1.000 MB", "{}", .{fmtByteCountIEC(std.math.pow(u64, 1024, 2))});
+    try std.testing.expectFmt("1.000 MB", "{f}", .{fmtByteCountIEC(std.math.pow(u64, 1024, 2))});
 }
 test {
-    try std.testing.expectFmt("1.000 GB", "{}", .{fmtByteCountIEC(std.math.pow(u64, 1024, 3))});
+    try std.testing.expectFmt("1.000 GB", "{f}", .{fmtByteCountIEC(std.math.pow(u64, 1024, 3))});
 }
diff --git a/src/fmtReplacer.zig b/src/fmtReplacer.zig
index 94185122fc9b8673b46b6b35cbfc79297ca6359d..29f0608eecaafeef08c9c0291a95f919be2ee9c3 100644
--- a/src/fmtReplacer.zig
+++ b/src/fmtReplacer.zig
@@ -2,7 +2,7 @@ const std = @import("std");
 const string = []const u8;
 const extras = @import("./lib.zig");
 
-pub fn fmtReplacer(bytes: string, from: u8, to: u8) std.fmt.Formatter(formatReplacer) {
+pub fn fmtReplacer(bytes: string, from: u8, to: u8) std.fmt.Alt(FormatData, formatReplacer) {
     return .{ .data = .{
         .bytes = bytes,
         .from = from,
@@ -18,12 +18,8 @@ const FormatData = struct {
 
 fn formatReplacer(
     self: FormatData,
-    comptime fmt: []const u8,
-    options: std.fmt.FormatOptions,
-    writer: anytype,
+    writer: *std.Io.Writer,
 ) !void {
-    _ = fmt;
-    _ = options;
     for (self.bytes) |c| {
         try writer.writeByte(if (c == self.from) self.to else @intCast(c));
     }
@@ -32,5 +28,5 @@ fn formatReplacer(
 test {
     const in = "C:\\Program Files\\Custom Utilities\\StringFinder.exe";
     const out = "C:/Program Files/Custom Utilities/StringFinder.exe";
-    try std.testing.expectFmt(out, "{}", .{fmtReplacer(in, '\\', '/')});
+    try std.testing.expectFmt(out, "{f}", .{fmtReplacer(in, '\\', '/')});
 }
diff --git a/src/mapBy.zig b/src/mapBy.zig
index 3038acd543c3ccfc0b988e7c741d6e7edb455fa5..6f063b0da9f63999a2be1de23c9a7e10f451b14f 100644
--- a/src/mapBy.zig
+++ b/src/mapBy.zig
@@ -2,8 +2,8 @@ const std = @import("std");
 const string = []const u8;
 const extras = @import("./lib.zig");
 
-pub fn mapBy(allocator: std.mem.Allocator, slice: anytype, comptime field: std.meta.FieldEnum(std.meta.Elem(@TypeOf(slice)))) ![]std.meta.FieldType(std.meta.Elem(@TypeOf(slice)), field) {
-    const newslice = try allocator.alloc(std.meta.FieldType(std.meta.Elem(@TypeOf(slice)), field), slice.len);
+pub fn mapBy(allocator: std.mem.Allocator, slice: anytype, comptime field: std.meta.FieldEnum(std.meta.Elem(@TypeOf(slice)))) ![]@FieldType(std.meta.Elem(@TypeOf(slice)), @tagName(field)) {
+    const newslice = try allocator.alloc(@FieldType(std.meta.Elem(@TypeOf(slice)), @tagName(field)), slice.len);
     for (newslice, slice) |*i, j| i.* = @field(j, @tagName(field));
     return newslice;
 }
diff --git a/src/pipe.zig b/src/pipe.zig
index c636c1514ee073f1e54017bb3bc109379d2a4d29..8f43e87da2a2ea75c9cb2e4400355af817a88b67 100644
--- a/src/pipe.zig
+++ b/src/pipe.zig
@@ -15,8 +15,8 @@ test {
     const bytes = "abcdefghijklmnopqrstuvwxyz".*;
     var fba = std.io.fixedBufferStream(&bytes);
     const allocator = std.testing.allocator;
-    var list = std.ArrayList(u8).init(allocator);
+    var list = std.Io.Writer.Allocating.init(allocator);
     defer list.deinit();
-    try pipe(fba.reader(), list.writer());
-    try std.testing.expect(std.mem.eql(u8, &bytes, list.items));
+    try pipe(fba.reader(), &list.writer);
+    try std.testing.expect(std.mem.eql(u8, &bytes, list.written()));
 }
diff --git a/src/reduceNumber.zig b/src/reduceNumber.zig
index ad4a73cc8e2a85394bd90730779b1bd49be00d45..b00c4577cf8e0c737bc993512f345edcae4a47f4 100644
--- a/src/reduceNumber.zig
+++ b/src/reduceNumber.zig
@@ -21,29 +21,29 @@ pub fn reduceNumber(writer: anytype, input: u64, comptime unit: u64, comptime ba
 
 test {
     const allocator = std.testing.allocator;
-    var list = std.ArrayList(u8).init(allocator);
+    var list = std.Io.Writer.Allocating.init(allocator);
     defer list.deinit();
-    try reduceNumber(list.writer(), 1, 60, "s", "mh");
-    try std.testing.expect(std.mem.eql(u8, list.items, "1 s"));
+    try reduceNumber(&list.writer, 1, 60, "s", "mh");
+    try std.testing.expect(std.mem.eql(u8, list.written(), "1 s"));
 }
 test {
     const allocator = std.testing.allocator;
-    var list = std.ArrayList(u8).init(allocator);
+    var list = std.Io.Writer.Allocating.init(allocator);
     defer list.deinit();
-    try reduceNumber(list.writer(), 60, 60, "s", "mh");
-    try std.testing.expect(std.mem.eql(u8, list.items, "1.000 ms"));
+    try reduceNumber(&list.writer, 60, 60, "s", "mh");
+    try std.testing.expect(std.mem.eql(u8, list.written(), "1.000 ms"));
 }
 test {
     const allocator = std.testing.allocator;
-    var list = std.ArrayList(u8).init(allocator);
+    var list = std.Io.Writer.Allocating.init(allocator);
     defer list.deinit();
-    try reduceNumber(list.writer(), 3600, 60, "s", "mh");
-    try std.testing.expect(std.mem.eql(u8, list.items, "1.000 hs"));
+    try reduceNumber(&list.writer, 3600, 60, "s", "mh");
+    try std.testing.expect(std.mem.eql(u8, list.written(), "1.000 hs"));
 }
 test {
     const allocator = std.testing.allocator;
-    var list = std.ArrayList(u8).init(allocator);
+    var list = std.Io.Writer.Allocating.init(allocator);
     defer list.deinit();
-    try reduceNumber(list.writer(), 216000, 60, "s", "mh");
-    try std.testing.expect(std.mem.eql(u8, list.items, "60.000 hs"));
+    try reduceNumber(&list.writer, 216000, 60, "s", "mh");
+    try std.testing.expect(std.mem.eql(u8, list.written(), "60.000 hs"));
 }