How to fix an error when trying to open Telegram or Slack on Firefox

If you’re getting an NS_ERROR_DOM_ABORT_ERR while trying to open web.telegram.org or app.slack.com on Firefox 87 or above, or if these pages aren’t loading at all, here’s a workaround you can try:

1. Enter about:serviceworkers in the address bar.
2. Click Unregister for the site you’re trying to visit.
3. Reload the site.
4. If the site still isn’t loading properly, clear the storage for that site (see Clear cookies and site data for more information.)