If you include links in your post, they must begin with `http://` or `https://`. All links are counted as 23 characters, no matter how long they actually are, so there is no need to use a link shortener to save characters. In fact, using a link shortener is actively discouraged.
You can mention users by typing out their full address, e.g. `@alice@example.com`. Note that any usage of`@word` will be interpreted as mentioning the local user with the username `word`, if that user exists. Only the username part will count against your character limit -- the domain is not counted.
You can use a `#hashtag` to make your post discoverable to anyone searching for that hashtag. Hashtags can contain alphanumeric characters and underscores, but cannot contain numbers only.
Each server offers a set of custom emoji you can use, like on Discord. You can use an emoji using its shortcode like `:thounking:`, or by clicking the emoji face in the compose box and browsing through the "Custom" category. You can also browse through and search for standard unicode emoji.
* **Images** (PNG, JPG, GIF) **up to 8MB**. Images will be downscaled to 1.6 megapixels (enough for a 1280x1280 image). Up to 4 images can be attached.
* **Animated GIFs** are converted to soundless MP4s like on Imgur/Gfycat (**GIFV**). You can also upload soundless MP4 and WebM, which will be handled the same way.
* **Videos** (MP4, M4V, MOV, WebM) **up to 40MB**. Video will be transcoded to H.264 MP4 with a maximum bitrate of 1300kbps and framerate of 60fps.
* **Audio** (MP3, OGG, WAV, FLAC, OPUS, AAC, M4A, 3GP) **up to 40MB**. Audio will be transcoded to MP3 using V2 VBR (roughly 192kbps).
By clicking the "Edit" link on the attachment thumbnail, you can load a modal which will allow adding a media description or changing the focal point. Although optional, it is a good idea to add media descriptions that briefly describe what is in contained in the media. These descriptions will be shown when the media fails to load for any reason, or when accessed by screen readers and other assistive technology. Setting the focal point is also optional, but can make preview thumbnails looks better when they are not shown in a 16:9 aspect ratio.
Posts can be published with one of four different privacy levels, as described below. You can [set a default privacy level for your posts](../preferences#posting), and you can change the privacy level for a draft post by selecting the "Change Post Privacy" icon beneath the text of the post.
* Seeing your post at the permalink requires being logged in on the same website as someone who was mentioned.
* Your post will not appear in-app except to anyone mentioned.
* Anyone mentioned will receive the post in notifications. It will not appear in the home timeline.
* Your post cannot be boosted.
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**Do not share dangerous and sensitive information over direct messages**. Mastodon is not an encrypted messaging app like Signal or Wire, the database administrators of the sender’s and recipient’s servers have access to the text. Use them with the same caution as you would use forum PMs, Discord PMs and Twitter DMs.
One feature that Mastodon provides that you may not have seen on other social networks is the option to attach a content warning to your posts. When a content warning is included, the status content will be collapsed by default, and only the CW will be shown, similarly to an email subject line or a "read more" break. This can be used to add a summary or subject for your post, to collapse long posts, or to otherwise provide context or setup for the body of the post.
When media is attached, a checkbox appears to allow you to "mark media as sensitive". This hides the full media behind a blurred thumbnail by default. Adding a CW to a post automatically marks the media as sensitive as well.
