diff --git a/app/hooks/use-form.ts b/app/hooks/use-form.ts
new file mode 100644
index 0000000..d8e57db
--- /dev/null
+++ b/app/hooks/use-form.ts
@@ -0,0 +1,181 @@
+import { type, type Type } from "arktype";
+import { useCallback, useEffect, useMemo, useRef, useState } from "react";
+
+type FormValue = string | number | boolean | null;
+
+interface FormState {
+  values: Record<string, FormValue>;
+  errors: Record<string, string>;
+  modified: Record<string, boolean>;
+}
+
+export interface FormFieldProps {
+  name: string;
+  value: string;
+  onChange: (value: string) => void;
+  onBlur: () => void;
+  invalid: boolean;
+  errorMessage?: string;
+}
+
+interface UseFormOptions<T extends Record<string, unknown>> {
+  schema: Type<T>;
+  defaultValues?: Partial<Record<keyof T & string, FormValue>>;
+  actionData?: unknown;
+  validate?: (values: Record<string, FormValue>) => Record<string, string> | undefined;
+}
+
+// arktype's Type<T> doesn't expose `.props` in the type system,
+// but it exists at runtime. This extracts schema keys safely.
+function schemaKeys(schema: Type): string[] {
+  const props = (schema as unknown as { props?: { key: string }[] }).props;
+  return props?.map((p) => p.key) ?? [];
+}
+
+export function useForm<T extends Record<string, unknown>>(options: UseFormOptions<T>) {
+  const { schema, actionData, validate } = options;
+  const keys = schemaKeys(schema);
+  const validateRef = useRef(validate);
+  validateRef.current = validate;
+
+  const initialValues = useMemo(() => {
+    const values: Record<string, FormValue> = {};
+    for (const key of keys) {
+      values[key] =
+        options.defaultValues && key in options.defaultValues
+          ? (options.defaultValues[key as keyof T & string] as FormValue)
+          : "";
+    }
+    return values;
+  }, []);
+
+  const [state, setState] = useState<FormState>({
+    values: initialValues,
+    errors: {},
+    modified: {},
+  });
+
+  useEffect(() => {
+    if (actionData && typeof actionData === "object" && "errors" in actionData) {
+      const errors = actionData.errors as Record<string, string>;
+      setState((prev) => ({
+        ...prev,
+        errors: { ...prev.errors, ...errors },
+      }));
+    }
+  }, [actionData]);
+
+  const setValue = useCallback((name: keyof T & string, raw: FormValue) => {
+    setState((prev) => ({
+      ...prev,
+      values: { ...prev.values, [name]: raw },
+      modified: { ...prev.modified, [name]: true },
+    }));
+  }, []);
+
+  function validateField(name: string) {
+    if (!state.modified[name]) {
+      return;
+    }
+
+    const errors: Record<string, string> = {};
+
+    // Schema validation
+    const result = schema({ ...state.values } as never);
+    if (result instanceof type.errors) {
+      const fieldProblems = result.flatProblemsByPath[name];
+      if (fieldProblems) {
+        errors[name] = fieldProblems[0];
+      }
+    }
+
+    // Cross-field validation
+    if (!errors[name]) {
+      const customErrors = validateRef.current?.(state.values);
+      if (customErrors?.[name]) {
+        errors[name] = customErrors[name];
+      }
+    }
+
+    setState((prev) => ({
+      ...prev,
+      errors: {
+        ...prev.errors,
+        [name]: errors[name] ?? "",
+      },
+    }));
+  }
+
+  function field(name: keyof T & string): FormFieldProps {
+    const error = state.errors[name];
+    return {
+      name,
+      value: String(state.values[name] ?? ""),
+      onChange: (value: string) => setValue(name, value),
+      onBlur: () => validateField(name),
+      invalid: !!error,
+      errorMessage: error || undefined,
+    };
+  }
+
+  function computeCanSubmit(): boolean {
+    const result = schema({ ...state.values } as never);
+    if (result instanceof type.errors) {
+      return false;
+    }
+
+    const customErrors = validateRef.current?.(state.values);
+    if (customErrors && Object.values(customErrors).some(Boolean)) {
+      return false;
+    }
+
+    return true;
+  }
+
+  const reset = useCallback(() => {
+    setState({
+      values: { ...initialValues },
+      errors: {},
+      modified: {},
+    });
+  }, [initialValues]);
+
+  return {
+    values: state.values,
+    errors: state.errors,
+    field,
+    canSubmit: computeCanSubmit(),
+    setValue,
+    reset,
+  };
+}
+
+type ServerValidationResult<T> =
+  | { success: true; data: T }
+  | { success: false; errors: Record<string, string> };
+
+export async function validateFormData<T extends Record<string, unknown>>(
+  request: Request,
+  schema: Type<T>,
+): Promise<ServerValidationResult<T>> {
+  const formData = await request.formData();
+  const parsed: Record<string, unknown> = {};
+
+  for (const key of schemaKeys(schema)) {
+    const raw = formData.get(key);
+    if (raw !== null) {
+      parsed[key] = raw.toString();
+    }
+  }
+
+  const result = schema(parsed as never);
+  if (result instanceof type.errors) {
+    const errors: Record<string, string> = {};
+    for (const [path, problems] of Object.entries(result.flatProblemsByPath)) {
+      errors[path] = problems[0];
+    }
+    return { success: false, errors };
+  }
+
+  return { success: true, data: result as T };
+}
diff --git a/app/routes/dns/dialogs/add-ns.tsx b/app/routes/dns/dialogs/add-ns.tsx
index 985d0ed..23c7212 100644
--- a/app/routes/dns/dialogs/add-ns.tsx
+++ b/app/routes/dns/dialogs/add-ns.tsx
@@ -1,5 +1,5 @@
+import { type } from "arktype";
 import { Split } from "lucide-react";
-import { useMemo, useState } from "react";
 
 import Button from "~/components/button";
 import Chip from "~/components/chip";
@@ -9,30 +9,40 @@ import Switch from "~/components/switch";
 import Text from "~/components/text";
 import Title from "~/components/title";
 import Tooltip from "~/components/tooltip";
+import { useForm } from "~/hooks/use-form";
 import cn from "~/utils/cn";
 
+const nsSchema = type({
+  ns: "string.ip",
+  split_name: "string > 0",
+});
+
 interface Props {
   nameservers: Record<string, string[]>;
 }
 
 export default function AddNameserver({ nameservers }: Props) {
-  const [split, setSplit] = useState(false);
-  const [ns, setNs] = useState("");
-  const [domain, setDomain] = useState("");
+  const form = useForm({
+    schema: nsSchema,
+    defaultValues: { split_name: "global" },
+    validate: (values) => {
+      const ns = values.ns as string;
+      const domain = values.split_name as string;
+      if (!ns) return undefined;
 
-  const isInvalid = useMemo(() => {
-    if (ns === "") return false;
-    // Test if it's a valid IPv4 or IPv6 address
-    const ipv4 = /^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$/;
-    const ipv6 = /^([0-9a-fA-F:]+:+)+[0-9a-fA-F]+$/;
-    if (!ipv4.test(ns) && !ipv6.test(ns)) return true;
+      const isSplit = domain !== "global";
+      const isDuplicate = isSplit
+        ? nameservers[domain]?.includes(ns)
+        : Object.values(nameservers).some((nsList) => nsList.includes(ns));
 
-    if (split) {
-      return nameservers[domain]?.includes(ns);
-    }
+      if (isDuplicate) {
+        return { ns: "This nameserver already exists." };
+      }
 
-    return Object.values(nameservers).some((nsList) => nsList.includes(ns));
-  }, [nameservers, ns]);
+      return undefined;
+    },
+  });
+  const split = (form.values.split_name as string) !== "global";
 
   return (
     <Dialog>
@@ -41,12 +51,10 @@ export default function AddNameserver({ nameservers }: Props) {
         <Title className="mb-4">Add nameserver</Title>
         <input name="action_id" type="hidden" value="add_ns" />
         <Input
+          {...form.field("ns")}
           description="Use this IPv4 or IPv6 address to resolve names."
-          invalid={isInvalid}
           required
           label="Nameserver"
-          name="ns"
-          onChange={setNs}
           placeholder="1.2.3.4"
         />
         <div className="mt-8 flex items-center justify-between">
@@ -67,16 +75,20 @@ export default function AddNameserver({ nameservers }: Props) {
             </div>
             <Text className="text-sm">This nameserver will only be used for some domains.</Text>
           </div>
-          <Switch label="Split DNS" onCheckedChange={setSplit} />
+          <Switch
+            label="Split DNS"
+            onCheckedChange={(checked) => {
+              form.setValue("split_name", checked ? "" : "global");
+            }}
+          />
         </div>
         {split ? (
           <>
             <Text className="mt-8 font-semibold">Domain</Text>
             <Input
-              required={split === true}
+              {...form.field("split_name")}
+              required
               label="Domain"
-              name="split_name"
-              onChange={setDomain}
               placeholder="example.com"
             />
             <Text className="text-sm">
diff --git a/app/routes/dns/dialogs/add-record.tsx b/app/routes/dns/dialogs/add-record.tsx
index dec86fd..a8b0c1f 100644
--- a/app/routes/dns/dialogs/add-record.tsx
+++ b/app/routes/dns/dialogs/add-record.tsx
@@ -1,4 +1,4 @@
-import { useMemo, useState } from "react";
+import { type } from "arktype";
 
 import Button from "~/components/button";
 import Code from "~/components/code";
@@ -7,33 +7,49 @@ import Input from "~/components/input";
 import Select from "~/components/select";
 import Text from "~/components/text";
 import Title from "~/components/title";
+import { useForm } from "~/hooks/use-form";
+
+const recordSchema = type({
+  record_type: "'A' | 'AAAA'",
+  record_name: "string > 0",
+  record_value: "string > 0",
+});
 
 interface Props {
   records: { name: string; type: "A" | "AAAA" | string; value: string }[];
 }
 
 export default function AddRecord({ records }: Props) {
-  const [type, setType] = useState<"A" | "AAAA" | string>("A");
-  const [name, setName] = useState("");
-  const [ip, setIp] = useState("");
+  const form = useForm({
+    schema: recordSchema,
+    defaultValues: { record_type: "A" },
+    validate: (values) => {
+      const name = values.record_name as string;
+      const ip = values.record_value as string;
+      if (name.length === 0 || ip.length === 0) return undefined;
 
-  const isDuplicate = useMemo(() => {
-    if (name.length === 0 || ip.length === 0) return false;
-    const lookup = records.find((record) => record.name === name);
-    if (!lookup) return false;
+      const lookup = records.find((r) => r.name === name);
+      if (lookup?.value === ip) {
+        return {
+          record_name: "This record already exists.",
+          record_value: "This record already exists.",
+        };
+      }
 
-    return lookup.value === ip;
-  }, [records, name, ip]);
+      return undefined;
+    },
+  });
+  const name = form.values.record_name as string;
+  const ip = form.values.record_value as string;
+  const recordType = form.values.record_type as string;
+  const isDuplicate =
+    !!form.errors.record_name?.includes("already exists") &&
+    !!form.errors.record_value?.includes("already exists");
 
   return (
     <Dialog>
       <Button>Add DNS record</Button>
-      <DialogPanel
-        onSubmit={() => {
-          setName("");
-          setIp("");
-        }}
-      >
+      <DialogPanel onSubmit={() => form.reset()}>
         <Title>Add DNS record</Title>
         <Text>Enter the domain and IP address for the new DNS record.</Text>
         <div className="mt-4 flex flex-col gap-2">
@@ -42,9 +58,9 @@ export default function AddRecord({ records }: Props) {
             required
             label="Record Type"
             name="record_type"
-            defaultValue={type}
+            defaultValue={recordType}
             onValueChange={(v) => {
-              if (v) setType(v as "A" | "AAAA");
+              if (v) form.setValue("record_type", v);
             }}
             items={[
               { value: "A", label: "A" },
@@ -52,20 +68,16 @@ export default function AddRecord({ records }: Props) {
             ]}
           />
           <Input
+            {...form.field("record_name")}
             required
             label="Domain"
             placeholder="test.example.com"
-            name="record_name"
-            onChange={setName}
-            invalid={isDuplicate}
           />
           <Input
+            {...form.field("record_value")}
             required
             label="IP Address"
-            placeholder={type === "AAAA" ? "2001:db8::ff00:42:8329" : "101.101.101.101"}
-            name="record_value"
-            onChange={setIp}
-            invalid={isDuplicate}
+            placeholder={recordType === "AAAA" ? "2001:db8::ff00:42:8329" : "101.101.101.101"}
           />
           {isDuplicate ? (
             <p className="text-sm opacity-50">
diff --git a/app/routes/machines/dialogs/new.tsx b/app/routes/machines/dialogs/new.tsx
index 2555dd8..3f5ebd8 100644
--- a/app/routes/machines/dialogs/new.tsx
+++ b/app/routes/machines/dialogs/new.tsx
@@ -1,3 +1,4 @@
+import { type } from "arktype";
 import { Computer, FileKey2 } from "lucide-react";
 import { useState } from "react";
 import { useNavigate } from "react-router";
@@ -9,9 +10,15 @@ import { Menu, MenuContent, MenuItem, MenuTrigger } from "~/components/menu";
 import Select from "~/components/select";
 import Text from "~/components/text";
 import Title from "~/components/title";
+import { useForm } from "~/hooks/use-form";
 import type { User } from "~/types";
 import { getUserDisplayName } from "~/utils/user";
 
+const registerSchema = type({
+  register_key: "string == 24",
+  user: "string > 0",
+});
+
 export interface NewMachineProps {
   server: string;
   users: User[];
@@ -21,15 +28,13 @@ export interface NewMachineProps {
 
 export default function NewMachine(data: NewMachineProps) {
   const [pushDialog, setPushDialog] = useState(false);
-  const [mkey, setMkey] = useState("");
+  const form = useForm({ schema: registerSchema });
   const navigate = useNavigate();
 
-  const isMkeyInvalid = mkey.length > 0 && mkey.length !== 24;
-
   return (
     <>
       <Dialog isOpen={pushDialog} onOpenChange={setPushDialog}>
-        <DialogPanel isDisabled={mkey.length !== 24}>
+        <DialogPanel isDisabled={!form.canSubmit}>
           <Title>Register Machine Key</Title>
           <Text className="mb-4">
             The machine key is given when you run{" "}
@@ -37,18 +42,16 @@ export default function NewMachine(data: NewMachineProps) {
           </Text>
           <input name="action_id" type="hidden" value="register" />
           <Input
-            errorMessage="Machine key must be exactly 24 characters"
-            invalid={isMkeyInvalid}
+            {...form.field("register_key")}
             required
             label="Machine Key"
-            name="register_key"
-            onChange={setMkey}
             placeholder="AbCd..."
           />
           <Select
             required
             label="Owner"
             name="user"
+            onValueChange={(v) => form.setValue("user", v)}
             placeholder="Select a user"
             items={data.users.map((user) => ({
               value: user.id,
diff --git a/app/routes/machines/dialogs/rename.tsx b/app/routes/machines/dialogs/rename.tsx
index f5e0f4d..3384d83 100644
--- a/app/routes/machines/dialogs/rename.tsx
+++ b/app/routes/machines/dialogs/rename.tsx
@@ -1,12 +1,17 @@
-import { useState } from "react";
+import { type } from "arktype";
 
 import Code from "~/components/code";
 import Dialog, { DialogPanel } from "~/components/dialog";
 import Input from "~/components/input";
 import Text from "~/components/text";
 import Title from "~/components/title";
+import { useForm } from "~/hooks/use-form";
 import type { Machine } from "~/types";
 
+const renameSchema = type({
+  name: "string > 0",
+});
+
 interface RenameProps {
   machine: Machine;
   isOpen: boolean;
@@ -15,7 +20,11 @@ interface RenameProps {
 }
 
 export default function Rename({ machine, magic, isOpen, setIsOpen }: RenameProps) {
-  const [name, setName] = useState(machine.givenName);
+  const form = useForm({
+    schema: renameSchema,
+    defaultValues: { name: machine.givenName },
+  });
+  const name = form.values.name as string;
 
   return (
     <Dialog isOpen={isOpen} onOpenChange={setIsOpen}>
@@ -27,14 +36,7 @@ export default function Rename({ machine, magic, isOpen, setIsOpen }: RenameProp
         </Text>
         <input name="action_id" type="hidden" value="rename" />
         <input name="node_id" type="hidden" value={machine.id} />
-        <Input
-          defaultValue={machine.givenName}
-          required
-          label="Machine name"
-          name="name"
-          onChange={setName}
-          placeholder="Machine name"
-        />
+        <Input {...form.field("name")} required label="Machine name" placeholder="Machine name" />
         {magic ? (
           name.length > 0 && name !== machine.givenName ? (
             <p className="mt-2 text-sm leading-tight text-mist-600 dark:text-mist-300">
diff --git a/app/routes/settings/restrictions/dialogs/add-domain.tsx b/app/routes/settings/restrictions/dialogs/add-domain.tsx
index 64efb46..9a54b36 100644
--- a/app/routes/settings/restrictions/dialogs/add-domain.tsx
+++ b/app/routes/settings/restrictions/dialogs/add-domain.tsx
@@ -1,10 +1,15 @@
-import { useMemo, useState } from "react";
+import { type } from "arktype";
 
 import Button from "~/components/button";
 import Dialog, { DialogPanel } from "~/components/dialog";
 import Input from "~/components/input";
 import Text from "~/components/text";
 import Title from "~/components/title";
+import { useForm } from "~/hooks/use-form";
+
+const domainSchema = type({
+  domain: "string > 0",
+});
 
 interface AddDomainProps {
   domains: string[];
@@ -12,27 +17,29 @@ interface AddDomainProps {
 }
 
 export default function AddDomain({ domains, isDisabled }: AddDomainProps) {
-  const [domain, setDomain] = useState("");
+  const form = useForm({
+    schema: domainSchema,
+    validate: (values) => {
+      const domain = (values.domain as string).trim();
+      if (domain.length === 0) return undefined;
 
-  const isInvalid = useMemo(() => {
-    if (!domain || domain.trim().length === 0) {
-      // Empty domain is invalid, but no error shown
-      return false;
-    }
+      if (domains.includes(domain)) {
+        return { domain: "This domain already exists in the list." };
+      }
 
-    if (domains.includes(domain.trim())) {
-      return true;
-    }
+      try {
+        const url = new URL(`http://${domain}`);
+        if (url.hostname !== domain) {
+          return { domain: "This is not a valid domain." };
+        }
+      } catch {
+        return { domain: "This is not a valid domain." };
+      }
 
-    try {
-      // Check if domain is a valid FQDN
-      const url = new URL(`http://${domain.trim()}`);
-      return url.hostname !== domain.trim();
-    } catch (e) {
-      // If URL constructor fails, it's not a valid domain
-      return true;
-    }
-  }, [domain, domains]);
+      return undefined;
+    },
+  });
+  const domain = (form.values.domain as string).trim();
 
   return (
     <Dialog>
@@ -45,23 +52,16 @@ export default function AddDomain({ domains, isDisabled }: AddDomainProps) {
         </Text>
         <input name="action_id" type="hidden" value="add_domain" />
         <Input
+          {...form.field("domain")}
           description={
-            domain.trim().length > 0
-              ? `Matches users with <user>@${domain.trim()}`
+            domain.length > 0
+              ? `Matches users with <user>@${domain}`
               : "Enter a domain to match users with their email addresses."
           }
-          invalid={domain.trim().length === 0 || isInvalid}
           required
           label="Domain"
-          name="domain"
-          onChange={setDomain}
           placeholder="example.com"
         />
-        {isInvalid && (
-          <p className="mt-2 text-sm text-red-500">
-            The domain you entered is invalid or already exists in the list.
-          </p>
-        )}
       </DialogPanel>
     </Dialog>
   );
diff --git a/app/routes/settings/restrictions/dialogs/add-group.tsx b/app/routes/settings/restrictions/dialogs/add-group.tsx
index 415cb55..e831b33 100644
--- a/app/routes/settings/restrictions/dialogs/add-group.tsx
+++ b/app/routes/settings/restrictions/dialogs/add-group.tsx
@@ -1,10 +1,15 @@
-import { useMemo, useState } from "react";
+import { type } from "arktype";
 
 import Button from "~/components/button";
 import Dialog, { DialogPanel } from "~/components/dialog";
 import Input from "~/components/input";
 import Text from "~/components/text";
 import Title from "~/components/title";
+import { useForm } from "~/hooks/use-form";
+
+const groupSchema = type({
+  group: "string > 0",
+});
 
 interface AddGroupProps {
   groups: string[];
@@ -12,18 +17,19 @@ interface AddGroupProps {
 }
 
 export default function AddGroup({ groups, isDisabled }: AddGroupProps) {
-  const [group, setGroup] = useState("");
+  const form = useForm({
+    schema: groupSchema,
+    validate: (values) => {
+      const group = (values.group as string).trim();
+      if (group.length === 0) return undefined;
 
-  const isInvalid = useMemo(() => {
-    if (!group || group.trim().length === 0) {
-      // Empty group is invalid, but no error shown
-      return false;
-    }
+      if (groups.includes(group)) {
+        return { group: "This group already exists in the list." };
+      }
 
-    if (groups.includes(group.trim())) {
-      return true;
-    }
-  }, [group, groups]);
+      return undefined;
+    },
+  });
 
   return (
     <Dialog>
@@ -35,19 +41,12 @@ export default function AddGroup({ groups, isDisabled }: AddGroupProps) {
         </Text>
         <input name="action_id" type="hidden" value="add_group" />
         <Input
+          {...form.field("group")}
           description="The group to allow for OIDC authentication."
-          invalid={group.trim().length === 0 || isInvalid}
           required
           label="Group"
-          name="group"
-          onChange={setGroup}
           placeholder="admin"
         />
-        {isInvalid && (
-          <p className="mt-2 text-sm text-red-500">
-            The group you entered already exists in the list of allowed groups.
-          </p>
-        )}
       </DialogPanel>
     </Dialog>
   );
diff --git a/app/routes/settings/restrictions/dialogs/add-user.tsx b/app/routes/settings/restrictions/dialogs/add-user.tsx
index d31c9b0..1df1fd6 100644
--- a/app/routes/settings/restrictions/dialogs/add-user.tsx
+++ b/app/routes/settings/restrictions/dialogs/add-user.tsx
@@ -1,10 +1,15 @@
-import { useMemo, useState } from "react";
+import { type } from "arktype";
 
 import Button from "~/components/button";
 import Dialog, { DialogPanel } from "~/components/dialog";
 import Input from "~/components/input";
 import Text from "~/components/text";
 import Title from "~/components/title";
+import { useForm } from "~/hooks/use-form";
+
+const userSchema = type({
+  user: "string > 0",
+});
 
 interface AddUserProps {
   users: string[];
@@ -12,18 +17,19 @@ interface AddUserProps {
 }
 
 export default function AddUser({ users, isDisabled }: AddUserProps) {
-  const [user, setUser] = useState("");
+  const form = useForm({
+    schema: userSchema,
+    validate: (values) => {
+      const user = (values.user as string).trim();
+      if (user.length === 0) return undefined;
 
-  const isInvalid = useMemo(() => {
-    if (!user || user.trim().length === 0) {
-      // Empty user is invalid, but no error shown
-      return false;
-    }
+      if (users.includes(user)) {
+        return { user: "This user already exists in the list." };
+      }
 
-    if (users.includes(user.trim())) {
-      return true;
-    }
-  }, [user, users]);
+      return undefined;
+    },
+  });
 
   return (
     <Dialog>
@@ -35,19 +41,12 @@ export default function AddUser({ users, isDisabled }: AddUserProps) {
         </Text>
         <input name="action_id" type="hidden" value="add_user" />
         <Input
+          {...form.field("user")}
           description="The user to allow for OIDC authentication."
-          invalid={user.trim().length === 0 || isInvalid}
           required
           label="User"
-          name="user"
-          onChange={setUser}
           placeholder="john_doe"
         />
-        {isInvalid && (
-          <p className="mt-2 text-sm text-red-500">
-            The user you entered already exists in the list of allowed users.
-          </p>
-        )}
       </DialogPanel>
     </Dialog>
   );