Attaching Files¶

Attachment Methods¶

Attach a file by drag and drop or by clicking the attachment icon in the message input box.

Drag and Drop¶

Upload a file or selection of files by dragging the files from your computer into the right-hand sidebar or center pane. Dragging and dropping attaches the files to the message input box, then you can optionally type a message and press ENTER to post.

Attachment Icon¶

Alternatively, upload files by clicking the grey paperclip icon inside the message input box. This opens up your system file viewer where you can navigate to the desired files and then click Open to upload the files to the message input box. Optionally type a message and then press ENTER to post.

Pasting Images¶

On Chrome and Edge browsers, it is also possible to upload files by pasting them from the clipboard. This is not yet supported on other browsers.

File Previewer¶

Mattermost has a built in file previewer that is used to view media, download files and share public links. Click the thumbnail of an attached file to open it in the file previewer.

Downloading Files¶

Download an attached file by clicking the download icon next to the file thumbnail or by opening the file previewer and clicking Download.

Supported Media Types¶

If you are trying to preview a media type that is not supported, the file previewer will open a standard media attachment icon. Supported media formats depend heavily on your browser and operating system, but the following formats are supported by Mattermost on most browsers:

Images: BMP, GIF, JPG, JPEG, PNG
Video: MP4
Audio: MP3, M4A
Files: PDF, TXT

Other document previews (Word, Excel, PPT) are not yet supported.

File Size Limitations¶

Mattermost supports a maximum of five attached files per post, each with a maximum file size of 50Mb.