The Join Captcha Bot: Group Protection

You opened your group to everyone, and an hour later it is full of ad links from accounts nobody invited. Spammers arrive in batches and post before a moderator can blink. The Join Captcha Bot puts a simple check at the entrance. 🛡️

A newcomer gets a captcha, and until it is solved, they do not belong in the group. The bot has been around for a while: about 18 thousand people use it each month.

How the check works

When someone joins, the bot sends an image with characters. They read it and type the answer. If they fail within the time limit, the bot removes them from the group.

Humans finish this in seconds. Automated accounts that blast ads in batches mostly drop out at this step. If someone joins several times in a row and never solves the captcha, the bot treats them as automated and bans them.

What you can tune

• Difficulty. The higher the level, the harder the image is to read. A middle level is enough for an ordinary group.
• Answer time. A very short limit annoys people, and a very long one leaves a window for spammers.
• Character set. Digits only are easier for people, letters with digits are harder to guess.
• Message language. The /language command switches the language the bot uses with members.

Help is always at hand: /help and /commands list everything the bot can do, and /about describes the project. 📋

Adding it to a group

1. Add the bot to your group.
2. Make it an admin with the right to delete messages and ban members. Without these rights the check will not work.
3. Turn on protection with the command that /help shows.
4. Test it: join the group from a spare account and solve the captcha yourself.

A test account takes a minute, and then you know newcomers cannot slip past. ✅

Pitfalls to know about

A captcha stops mass spam, but not everything. A live person who wants to harm your group will pass it easily. So it works as a first barrier, not as the only defense.

• Explain the rules in a pinned message. Some newcomers get scared and leave without understanding what is wanted.
• Do not make the captcha too hard. Real members will leave before the bots do.
• Combine tools. A captcha paired with restrictions on links and forwards for new members works well.

Who needs it

Owners of open chats, communities, support groups and discussions that anyone can enter by link. The more popular the group, the heavier the spam pressure.

Closed work chats with admin-only invitations usually do not need this protection.

Open source and limits

The bot is known as an open source project. That means outside developers can run their own copy on their own server if they want full control. Most admins are fine with the ready-made bot.

The bot posts update news in its info channel, linked in its profile. Before you trust any new tool, read which rights it asks from your group.