- Login to https://web.telegram.org
 - Copy-paste contents of 
telegram-scripts.jsinto JS console - Run 
showContacts()to get the list of contacts with ids - Run 
saveChat(userId)whereuserIdis the id from step 3 
Process can take a while, check console for progress. Occasionall FLOOD_WAIT errors are expected. Once done, browser will download the JSON file.