Telegram Bot sendMessage returns 400 error when posting to channel

Other Questions Telegram bot
1

I’m working with a custom Telegram bot library and keep getting Bad request 400 errors when trying to use the sendMessage method. I created a channel called “test_channel456” and my username is “user_test456”. I’m the admin and only member of this channel.

Here’s what I’ve tried:

bot_instance.post_message(chat_id="@test_channel456", message="hello world")

# also tried
bot_instance.post_message(chat_id="@test_channel456user_test456", message="hello world")

# and this
bot_instance.post_message(chat_id="@user_test456", message="hello world")

I think the issue might be with how I’m formatting the chat_id parameter. Are these approaches correct for targeting a channel or username? My other API calls work fine so the bot token should be valid.

2

Your bot probably isn’t an admin on the channel with posting permissions. Just creating the channel isn’t enough - the bot needs explicit access. Go to channel settings, add your bot as admin, and enable “Post Messages” permission. Then @test_channel456 as chat_id should work fine. I hit this same issue last month and wasted hours debugging before figuring out it was permissions. Also verify your channel username matches exactly what’s in the channel info - sometimes there are tiny differences that mess things up.

3

400 errors usually mean your chat_id format is wrong or the bot doesn’t have access. Make sure your channel username is exactly @test_channel456 - no extra characters. I’ve seen people accidentally copy invisible unicode stuff that breaks it. Also, don’t mix up channel usernames with personal ones. Your bot needs admin access to the channel before it can send messages. Try getting the numeric chat_id by forwarding a message from your channel to @RawDataBot - it’ll show you the exact format Telegram wants. Using the numeric ID usually fixes the formatting issues that cause 400 errors.

4

check if your channel’s public or private - the @ syntax only works for public channels with usernames. private channels need the actual numeric chat_id. forward a message from the channel to @userinfobot to get it. also make sure there’s no typos in the channel name.