Mastodon Content Warnings: What They Do and How to Write One

A content warning (CW) on Mastodon is a short line shown in place of your post, which stays collapsed until the reader chooses to open it. You add one with the CW button in the composer, and it counts toward your character limit and hides any attached media too.

What a content warning does

Mastodon's docs put it simply: with a content warning, the post's content is collapsed by default and only the warning is shown. Readers who want to see the post open it; readers who don't scroll past.

A CW also covers media. The docs say adding one "automatically marks the media as sensitive", so images and video sit behind a blurred preview. If you only want to blur an image and leave the text visible, there's a separate checkbox for that.

How to add a content warning

1. Open the composer and click the CW button at the bottom. Depending on your version and app, it may say Warning or show a ⚠️ icon.
2. Type the warning in the field that appears above your post.
3. Write the post as usual and publish.

Mastodon 4.5 added quote posts, and a CW on your quote hides the post you're quoting too. That's a way to share something with a warning its author didn't add, as long as they allow quotes.

When people use them

There's no single list, but fedi.tips and Hachyderm's community docs agree on the usual cases:

• Spoilers for films, shows, books and games.
• Upsetting news, including war, violence and disasters.
• Politics and religion. fedi.tips calls it a strong tradition on the fediverse.
• Personal trauma and topics like abuse or assault.
• Not safe for work content, such as nudity or gore.
• Images and topics some people need to avoid, which Hachyderm lists as faces making eye contact, food and alcohol, and weapons.

fedi.tips describes the point well: a CW is for content someone may not want to read right that minute but may want to read later. Your server can also make some of these a rule. Check its About page (https://your.server/about) for the rules your admins set.

How to write a good warning

fedi.tips' advice is to write a brief warning that gives people a clear idea of what to expect. Hachyderm suggests a test: if you didn't want to see this post, would the warning alone tell you to skip it?

A good warning names the topic, not your feelings about it, and says enough for someone to decide. It doesn't need to be a full sentence.

The warning counts toward your character limit

Mastodon checks a post's length by joining the warning and the text and counting both. So on a standard server with 500 characters, a 24-character warning like "Spoilers: Andor season 2" leaves 476 for the post. Links still count as 23 each, and mentions of people on other servers count only up to their username.

Two things follow from that:

• Keep the warning short. Every character in it comes out of your post.
• In a thread, warn each part. Each post collapses on its own, so a reply without a warning shows its text even if the first post had one. Repeating the warning costs its length in every part.

Our Mastodon character limit guide covers how to check your server's limit and what else counts.

What readers see and control

On the web, a post with a CW shows the warning and a button to reveal the rest. Readers have two shortcuts, both described by fedi.tips:

• Open a whole thread at once: the eye icon (👁️) at the top right of a thread opens or closes every collapsed post in it. In the mobile app, it works one post at a time.
• Never collapse anything: in Preferences, tick "Always expand posts marked with content warnings" and save.

So warnings cost little for readers who'd rather not see them: one setting turns them off. Readers who rely on them can still skip what they need to.

Content warnings on other networks

No other network hides a whole post's text behind a warning. Most have something for media:

A few details:

• Bluesky shows its content warning button only on a post with images, video or a link. The post schema describes these labels as "effectively content warnings", and the app's dialog asks you to add labels that apply to the media you're posting.
• Threads spoilers can hide parts of a post's text, up to 10 hidden ranges per post through Meta's API, or all of a post's media.
• X also has an account setting, "Mark media you post as containing material that may be sensitive", for accounts that post such media often.

Cross-posting a post that needs a warning

A Mastodon CW doesn't carry over anywhere else, because nothing else hides text the same way. When the same post goes to several networks:

1. Keep the CW on Mastodon. It's what readers there expect.
2. Put the warning in the first line elsewhere, so readers see it before the rest: "Spoilers for the Andor season 2 finale below."
3. Use the media options that exist: a label on Bluesky, a spoiler on Threads, the flag on X.
4. Ask whether the post belongs on every network. Something that needs a warning on Mastodon may not suit LinkedIn at all.

In Shaflex, the Mastodon copy of a draft has its own content warning field and a switch to mark media as sensitive. Set a warning and the media is marked sensitive too, the way Mastodon's own composer does it. Bluesky copies take Bluesky's labels for adult content and graphic media. Here's how to schedule Mastodon posts with a warning, and our alt text guide for describing the images behind it.

Sources

Checked on October 19, 2026.

• Mastodon docs: Posting toots (what a CW does, media marked sensitive)
• Mastodon source: StatusLengthValidator (the warning counts with the text)
• fedi.tips: How to use content warnings on Mastodon and the fediverse (adding a CW, uses, the eye icon, always expand, quoting with a CW)
• Hachyderm community docs: Content warnings
• AT Protocol lexicon: app.bsky.feed.post (self-labels, "effectively content warnings")
• Bluesky app source: LabelsBtn (label options) and Composer (shown with media or a link)
• Threads API docs: Spoilers
• X Help: Your media settings