diff --git a/types.ts b/types.ts
new file mode 100644
index 0000000..ec9ddd5
--- /dev/null
+++ b/types.ts
@@ -0,0 +1,28 @@
+import { JsonValue } from '@std/json'
+
+export type UUID = `${string}-${string}-${string}-${string}-${string}`
+export type DateString =
+	`${number}-${number}-${number}T${number}:${number}:${number}.${number}Z"`
+export type Login = `${string}.${string}`
+export type MailAddress = `${string}@${string}.${string}`
+
+export type ToJson<T> = T extends JsonValue ? T
+	: T extends { toJSON(): unknown } ? ReturnType<T['toJSON']>
+	: T extends { toJSON(): unknown }[]
+		? { [K: number]: ReturnType<T[typeof K]['toJSON']> }
+	: never
+
+export type MethodOf<T, K extends keyof T> = {
+	[P in keyof Pick<T, T[K] extends CallableFunction ? K : never>]: never
+}
+
+export type Serializable<T extends object> = {
+	[key in Exclude<keyof T, 'toJSON' | 'toString' | 'toPrimitive' | 'valueOf'>]:
+		ToJson<T[key]>
+}
+
+export type Posix = {
+	id: number
+	home: string
+	shell: string
+}