Mastodon Instance Custom Sign-Up Question: How to Add for Approval

Mastodon instance administrators often need to screen new registrations to keep their community focused and spam-free. The default sign-up form collects only a username, email, and password, which gives you no insight into why a person wants to join. Adding a custom sign-up question lets you ask applicants for a reason, an introduction, or a referral code before you approve or deny their account. This article explains how to enable registration review and add a custom text field to the sign-up form in a standard Mastodon instance.

What the Custom Sign-Up Question Feature Does

The custom sign-up question is a built-in feature of Mastodon, available in the administration panel of any instance running Mastodon version 3.0 or later. When you enable registration review, Mastodon holds new accounts in a pending state until an admin or moderator manually approves or rejects each one. The custom question appears as a text input field on the public sign-up page, below the standard fields for email, username, and password. The applicant’s answer is stored with their registration request and displayed in the pending accounts list inside the admin interface. You can use this question to collect a short introduction, a referral code, a reason for joining, or any other information that helps you decide whether to approve the account. No coding or custom development is required — the feature is available directly from the site settings. Before you begin, make sure you have admin access to the instance. Only users with the Administrator role can see and change these settings.

How to Add a Custom Sign-Up Question in Mastodon

Follow these steps to enable registration review and add a custom question to the sign-up form. You must be logged in as an administrator on the Mastodon instance.

1. Open the Administration section
   Click the Preferences link in the top-right navigation menu. Then click Administration in the left sidebar.
2. Go to Site Settings
   Under the Administration menu, click Site Settings. This page controls registration, branding, and content moderation settings for the entire instance.
3. Set Registration Mode to Approval Required
   Scroll to the Registrations section. Change the Registration mode dropdown from Open to Approval required. If you leave the mode set to Open, anyone can create an account immediately and the custom question will not be shown.
4. Write your custom sign-up question
   In the same section, locate the Sign-up question text field. Enter your question here. For example: “Why do you want to join this instance?” or “Please introduce yourself briefly.” Keep the question short — the field displays on the sign-up page as a single-line text input.
5. Add a hint for applicants (optional)
   Below the question field, you will see an empty text area labeled Registration question hint. Type a short example or instruction that appears as a tooltip or placeholder below the question on the sign-up form. For instance: “Example: I am a photographer looking for a community focused on digital art.”
6. Save the settings
   Scroll to the bottom of the page and click the Save changes button. The custom question will now appear on the sign-up page for all new visitors.

Common Mistakes and Things to Avoid

The custom question does not appear on the sign-up page

The most common reason is that the registration mode is still set to Open instead of Approval required. The custom question field only displays when approval is required. Go back to Site Settings and confirm that the dropdown shows Approval required. Also clear your browser cache or test the sign-up page in a private browsing window to see the most recent changes.

The question field is too long and cuts off on mobile

Mastodon does not enforce a strict character limit on the question, but the input field on the sign-up page is rendered as a standard text input, not a text area. Keep your question under 100 characters to avoid horizontal scrolling on smaller screens. If you need a longer prompt, use the hint field to provide additional context.

Applicants cannot see the question when using the Mastodon mobile app

The custom sign-up question only appears on the web-based sign-up page at your instance’s domain. Third-party mobile apps that use the Mastodon API to register accounts may not show the question at all. If you rely on the question for screening, direct new users to sign up through the web interface, not through an app.

Mastodon Registration Modes: Open vs Approval Required vs Closed

Item	Open Registration	Approval Required	Closed Registration
Custom question shown	No	Yes	No
Account creation flow	Instant, no review	Pending until admin approves	Sign-up form hidden
Best use case	Public instances with automated moderation	Invite-only or curated communities	Private instances for existing members

You can now control who joins your Mastodon instance by adding a custom sign-up question and requiring manual approval. Start by enabling Approval required in the Site Settings, then write a clear question that helps you evaluate applicants. For better community management, consider combining the question with a terms-of-service page or a welcome message that explains your instance’s rules. If you run a large instance, you can also assign moderators to help review pending registrations from the Administration > Accounts > Pending list.