diff --git a/.gitignore b/.gitignore
index 46a0161b..e581566e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@ node_modules/
 coverage/
 dist/
 .emscripten/
+.wit-bindgen/
 .e2e-results/
 .run-playwright/
 
diff --git a/argon2.wit b/argon2.wit
new file mode 100644
index 00000000..ba1c4392
--- /dev/null
+++ b/argon2.wit
@@ -0,0 +1,37 @@
+package phi-ag:argon2;
+
+interface types {
+  enum argon2-type {
+    argon2d,
+    argon2i,
+    argon2id
+  }
+
+  enum argon2-version {
+    version10,
+    version13,
+  }
+
+  record options {
+    hash-length: option<u32>,
+    time-cost: option<u32>,
+    memory-cost: option<u32>,
+    parallelism: option<u32>,
+    argon2-type: option<argon2-type>,
+    argon2-version: option<argon2-version>
+  }
+
+  record data {
+    encoded: string,
+    // TODO: Use fixed size lists, see https://github.com/bytecodealliance/wit-bindgen/pull/1277
+    hash: tuple<u8, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8>
+  }
+}
+
+world argon2 {
+  use types.{argon2-type, options, data};
+
+  export initialize: func();
+  export hash: func(password: string, salt: list<u8>, options: option<options>) -> result<data, string>;
+  export verify: func(encoded: string, password: string, argon2-type: option<argon2-type>) -> result<bool, string>;
+}