How to Add a Content Warning to a Mastodon Post

When you post about sensitive topics such as politics, violence, or spoilers, you may want to hide the content behind a warning label. Mastodon includes a built-in Content Warning feature that blurs or hides your post text until the reader clicks to reveal it. This article explains how to add a Content Warning to any new or existing Mastodon post on the web and mobile apps. You will learn the exact steps and understand when to use this feature.

What the Content Warning Feature Does and When to Use It

The Content Warning feature, sometimes called CW, lets you write a short label that appears in place of your full post. Readers see the label and a “Show more” link. They click the link to reveal the full text. This prevents people from seeing upsetting content without their consent.

Mastodon instances often have server rules that require Content Warnings for certain topics. Common use cases include discussions about mental health, death, violence, spoilers for movies or TV shows, and political content. Using a Content Warning is a sign of respect for your followers and helps maintain a safe environment.

The Content Warning applies only to the text of your post. Attachments such as images and videos have a separate setting called “Mark media as sensitive.” When you enable both, the text is hidden behind the warning label and the media is blurred until the reader clicks to view. You can use one or both features independently.

Prerequisites for Using Content Warnings

You need a Mastodon account on any instance. The feature works the same on mastodon.social, mastodon.online, and all other instances. The web interface and the official mobile apps for iOS and Android all include the Content Warning field. Third-party apps may place the field in a different location, but the concept is identical.

Steps to Add a Content Warning When Composing a New Post

Follow these steps to add a Content Warning to a new Mastodon post using the web interface. The mobile app steps are nearly identical; the field appears in the same position above the compose box.

1. Open the compose box
   Click the “What is on your mind?” text field at the top of the Home timeline or click the pencil icon in the top-right corner of the Mastodon web interface.
2. Locate the Content Warning field
   Look directly above the main compose box. The field is labeled “CW” or “Content warning” depending on your instance theme. It is a single-line text input.
3. Type your warning label
   Enter a short, clear description of what the post contains. Good examples: “Spoiler for Episode 5 of Severance,” “Discussion of anxiety and panic attacks,” or “Graphic description of a car accident.” Keep the label under 50 characters for readability.
4. Write your post in the main compose box
   Type the full content of your post in the larger text area below the CW field. The text will be hidden behind the warning label when the post is published.
5. Optionally mark media as sensitive
   If you attach images or videos, click the eye icon or the “Mark media as sensitive” checkbox below the compose box. This blurs the media preview until the reader clicks to view.
6. Publish the post
   Click the “Publish” button. Your post now appears in timelines with the warning label visible and the content hidden.

How to Add or Edit a Content Warning on an Existing Post

You can add a Content Warning to a post you already published, or change the existing label. This works on both the web interface and mobile apps.

1. Open the post you want to edit
   Navigate to the post on your profile or in a timeline. Click or tap the three-dot menu icon at the top-right of the post.
2. Select Edit
   From the menu, choose “Edit.” The post opens in a compose-like view with the current text and any existing Content Warning visible.
3. Modify the Content Warning field
   Type a new label in the CW field above the text box. If no CW exists, the field is empty. Type your label there. You can also clear the field to remove the Content Warning.
4. Save your changes
   Click the “Save” button. The updated post appears with the new Content Warning. Note that editing a post resets its timestamp and may cause the post to reappear in followers timelines.

Common Mistakes, Limitations, and Things to Avoid

Content Warning Not Appearing After Publishing

If you typed a label in the CW field but the post still shows full text, you likely placed the text in the main compose box instead of the CW field. Check that the label appears in the small single-line field above the main text area, not inside the large compose box. Delete the post and re-create it with the correct placement.

Media Still Visible Despite Content Warning

The Content Warning field only hides text. To hide images or videos, you must also check the “Mark media as sensitive” option. Without that checkbox, attached media appears normally even when the text is behind a CW. Always enable both when your post contains graphic visuals.

Warning Label Too Vague or Missing

A label like “Trigger warning” or “Sensitive content” does not tell readers what to expect. Write a specific description such as “Discussion of self-harm” or “Spoilers for The Last of Us episode 7.” Vague labels defeat the purpose of the feature because readers cannot make an informed choice about whether to view the content.

Editing a Post Removes Boosts and Favorites

When you edit a post to add or change a Content Warning, Mastodon removes all existing boosts and favorites. The post appears as a new version in timelines. If you want to preserve engagement, consider deleting the original post and publishing a new one with the CW instead of editing.

Content Warning vs Mark Media as Sensitive: When to Use Each

Item	Content Warning	Mark Media as Sensitive
What it hides	Text of the post	Images and videos attached to the post
Where to set it	Single-line CW field above the compose box	Checkbox or eye icon below the compose box
Reader action to reveal	Click “Show more” link on the post	Click the blurred media preview
Can be used alone	Yes	Yes
Best use case	Text-only sensitive discussions, spoilers	Graphic images, nudity, violence in visuals

By using the Content Warning feature and the Mark Media as Sensitive option together, you give readers full control over what they see on Mastodon. This is a core part of the platform culture and helps maintain a considerate community.