by bfontaine



Previewer is a quick hack around Mattermost’s inability to show previews for links other than images and YouTube videos. It’s like a proxy for your links: it acts as an image for Mattermost but will redirect any “normal” user to the original link.



Previewer requires Python 3.x. Install its dependencies:

pip install -r requirements.txt

Then run the app:

gunicorn app:app

Check gunicorn’s options for ports and more. There’s also Procfile and runtime.txt files for quick deployment on Heroku & friends (I use Flynn).


You have to build URLs by hand for now. Prepend <your previewer hostname> to your URL, and append /p.png at its end. Be careful that if your original URLs has parameter you need to put the /p.png before them.


In the examples below we assume you deployed your instance at

  • ->
  • ->
  • ->

How it works.

See my blog post.