outline/outline · error · Error

Must be a fully qualified domain name

Error message

Must be a fully qualified domain name

What it means

The IsFQDN decorator uses class-validator's isFQDN to ensure a model column holds a fully qualified domain name (e.g. sub.example.com). If the value fails FQDN rules (no dot, invalid chars, leading hyphen, etc.) the validator throws at save time.

Source

Thrown at server/models/validators/IsFQDN.ts:12

import { isFQDN } from "class-validator";
import { addAttributeOptions } from "sequelize-typescript";

/**
 * A decorator that validates that a string is a fully qualified domain name.
 */
export default function IsFQDN(target: object, propertyName: string) {
  return addAttributeOptions(target, propertyName, {
    validate: {
      validDomain(value: string) {
        if (!isFQDN(value)) {
          throw new Error("Must be a fully qualified domain name");
        }
      },
    },
  });
}

View on GitHub (pinned to 935a44d4c0)

Solutions

1. Provide a valid FQDN with at least one dot and a TLD (e.g. docs.example.com).
2. Validate the domain client-side with a regex or the same isFQDN before submitting.
3. Strip protocol/path (https://) from the input so only the host remains.

Example fix

// before
domain.host = 'https://docs.example.com/';

// after
domain.host = 'docs.example.com';

import { isFQDN } from 'class-validator';
if (!isFQDN(host)) {
  throw new ValidationError('Must be a fully qualified domain name');
}

import { isFQDN } from 'class-validator';
const isFqdn = (v: string): v is string => isFQDN(v);

When it happens

Trigger: Saving a model column decorated with @IsFQDN (commonly allowed domains / custom hostnames) with a non-domain string like 'localhost', 'my domain', 'a_b', or an IP address.

Common situations: Configuring a custom domain/subdomain feature with an invalid hostname; user-supplied domain input not sanitized; entering a bare TLD or single label.

Related errors

• Must be a valid hex color code
• Must be a valid url
• Must be a URL or relative path
• msg
• Invalid data

AI-assisted analysis of outline/outline@935a44d4c0 (2026-08-12). Data as JSON: /api/errors/9671de4efadfee2b. Report an issue: GitHub.