How to Monitor Public Telegram Channels for Free (No API Key, No Bot)

You can monitor public Telegram channels for free without needing an API key, bot, or server bill. The key is that Telegram provides a web preview at t.me/s/channel that returns the last ~20 posts as plain HTML. To monitor these posts, simply poll this URL periodically. The code loop imports the necessary libraries, gets the HTML from the URL with a 15-second timeout, and then uses a regular expression to find all message IDs in the HTML.

If a message ID hasn't been seen before, it's added to a set and printed as a new post. The script then sleeps for 5 minutes before checking again. The post IDs are sequential per channel, so a new max ID indicates a new post. The HTML contains subscriber counts, view counts, forward chains, media URLs, and more. However, this method only provides a window of the last ~20 posts, not a full history.

It also doesn't support private channels. To ensure deduplication across restarts, persist the seen message IDs to disk. The polling cadence is crucial, as 60 seconds would be too frequent for monitoring and 5 minutes is a good balance for alerts and research. This method has been used to monitor around 200 channels for market and OSINT signals.

The full collection-layer playbook, including cursor pagination, repost flags, and alerting, is available for $5 at a provided link.