diff --git a/app/assets/javascripts/discourse/app/mixins/password-validation.js b/app/assets/javascripts/discourse/app/mixins/password-validation.js
new file mode 100644
index 00000000000..50d89735ac2
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/mixins/password-validation.js
@@ -0,0 +1,121 @@
+import EmberObject, { computed } from "@ember/object";
+import Mixin from "@ember/object/mixin";
+import { isEmpty } from "@ember/utils";
+import { i18n } from "discourse-i18n";
+
+export default Mixin.create({
+  rejectedPasswords: null,
+
+  init() {
+    this._super(...arguments);
+    this.set("rejectedPasswords", []);
+    this.set("rejectedPasswordsMessages", new Map());
+  },
+
+  passwordInstructions: computed("passwordMinLength", function () {
+    return i18n("user.password.instructions", {
+      count: this.passwordMinLength,
+    });
+  }),
+
+  passwordMinLength: computed("isDeveloper", "admin", function () {
+    const { isDeveloper, admin } = this;
+    return isDeveloper || admin
+      ? this.siteSettings.min_admin_password_length
+      : this.siteSettings.min_password_length;
+  }),
+
+  passwordValidation: computed(
+    "accountPassword",
+    "passwordRequired",
+    "rejectedPasswords.[]",
+    "accountUsername",
+    "accountName",
+    "accountEmail",
+    "passwordMinLength",
+    "forceValidationReason",
+    function () {
+      const failedAttrs = {
+        failed: true,
+        ok: false,
+        element: document.querySelector("#new-account-password"),
+      };
+
+      if (!this.passwordRequired) {
+        return EmberObject.create({ ok: true });
+      }
+
+      if (this.rejectedPasswords.includes(this.accountPassword)) {
+        return EmberObject.create(
+          Object.assign(failedAttrs, {
+            reason:
+              this.rejectedPasswordsMessages.get(this.accountPassword) ||
+              i18n("user.password.common"),
+          })
+        );
+      }
+
+      // If blank, fail without a reason
+      if (isEmpty(this.accountPassword)) {
+        return EmberObject.create(
+          Object.assign(failedAttrs, {
+            message: i18n("user.password.required"),
+            reason: this.forceValidationReason
+              ? i18n("user.password.required")
+              : null,
+          })
+        );
+      }
+
+      // If too short
+      if (this.accountPassword.length < this.passwordMinLength) {
+        return EmberObject.create(
+          Object.assign(failedAttrs, {
+            reason: i18n("user.password.too_short", {
+              count: this.passwordMinLength,
+            }),
+          })
+        );
+      }
+
+      if (
+        !isEmpty(this.accountUsername) &&
+        this.accountPassword === this.accountUsername
+      ) {
+        return EmberObject.create(
+          Object.assign(failedAttrs, {
+            reason: i18n("user.password.same_as_username"),
+          })
+        );
+      }
+
+      if (
+        !isEmpty(this.accountName) &&
+        this.accountPassword === this.accountName
+      ) {
+        return EmberObject.create(
+          Object.assign(failedAttrs, {
+            reason: i18n("user.password.same_as_name"),
+          })
+        );
+      }
+
+      if (
+        !isEmpty(this.accountEmail) &&
+        this.accountPassword === this.accountEmail
+      ) {
+        return EmberObject.create(
+          Object.assign(failedAttrs, {
+            reason: i18n("user.password.same_as_email"),
+          })
+        );
+      }
+
+      // Looks good!
+      return EmberObject.create({
+        ok: true,
+        reason: i18n("user.password.ok"),
+      });
+    }
+  ),
+});