Open Extensions (the puzzle piece in Chrome's toolbar) and click Monday Miracle.
Log in to ESPN Fantasy if it asks you to, then choose Connect ESPN and approve.
The extension brings you back to this tab when ESPN is connected. Your ESPN leagues appear here.
ESPN connects from a computer. Open Monday Miracle in Chrome there and add the Monday Miracle extension. Your ESPN leagues then show up here too.
A league-mate's invite link needs no setup, on any device.
Advanced: paste espn_s2 and SWID yourself
For Firefox or Safari, or if you would rather not add an extension. Copy the two cookies your ESPN login sets:
Open ESPN Fantasy in another tab and log in
Press F12 or Ctrl+Shift+I (Windows) / Cmd+Option+I (Mac)
Click the Application tab
Expand Cookies in the left sidebar
Click on fantasy.espn.com
Find and copy espn_s2 (a long string) and SWID (a UUID in braces like {ABC-123...})
Open ESPN Fantasy in another tab and log in
Press F12 or Ctrl+Shift+I (Windows) / Cmd+Option+I (Mac)
Click the Storage tab
Expand Cookies in the left sidebar
Click on https://fantasy.espn.com
Find and copy the values for espn_s2 and SWID
Enable Developer Menu: Safari → Preferences → Advanced → Show Develop menu
Open ESPN Fantasy in another tab and log in
Press Cmd+Option+I to open Web Inspector
Click the Storage tab
Click on Cookies → fantasy.espn.com
Find and copy the values for espn_s2 and SWID
However ESPN connects, its two login cookies are stored encrypted on Monday Miracle's server and used only to read your ESPN leagues. Never shown to anyone. See the privacy policy.
Connect Sleeper
Type your Sleeper username and Monday Miracle reads every NFL league you are in this season. No password, and nothing to reconnect later.
Is this you on Sleeper?
Connect adds these leagues to your guide and changes nothing on Sleeper. Disconnect takes them out again.
Sleeper needs no password: Monday Miracle keeps your username, Sleeper's id for it and your display name, all public on Sleeper, and uses them only to read your leagues. Disconnect deletes all three. See the privacy policy.