🛡Telegram captcha bot for groups and channels — free, with rules

What's inside

• Chat rules before joining — your own text (age, swearing, ads) and an “I agree” checkbox.
• Three captcha types — pictures (“select all cats”), letters from an image or your own quiz question.
• Telegram Premium only — optional.
• Block new accounts — optional.
• Telegram's official join-request check: the captcha opens right inside the join request, and the bot approves or declines it itself.
• For groups and channels, free.

How the join captcha works

The captcha works through join requests. A person taps “Request to join” in your group or channel, and a check window opens right inside Telegram. First it shows the chat rules and an “I have read the rules and agree” checkbox, then the task itself. The check cannot be submitted without the tick.

If the task is solved, the request is approved automatically and the person is in the chat right away. There are three tries; after the third wrong answer the request is declined. If the window cannot be shown for some reason, the request is not lost and waits for the admins like a regular one.

The main difference from the usual captcha bots is the order. A typical bot lets a person into the group and only then asks them to press a button, while the rules sit in a pinned post few people open. Here the check happens before joining, and agreeing to the rules is a required part of it: only someone who has read and accepted them gets in.

Telegram's official join-request check

The captcha is built on a native Telegram mechanism: in a chat's join-request settings you can assign a bot that checks the requests (“join request queries” in the Bot API). Telegram hands each request to the checking bot, which shows the captcha window and tells Telegram to approve or decline.

As a result bots and spammers never appear in the chat even for a second, cannot read the conversation and do not get a “solve the captcha” message in the shared feed. The chat stays clean and members never see service messages about checks.

The admin does not have to go through requests by hand: approvals and declines happen without them. The @catalogue_app settings show whether it is assigned as the checker in the chat; if that last step is still missing, the bot points to where to find it.

Captcha types — pictures, letters and your own question

Pictures: pick the three matching images out of nine, for example “select all cats”. Letters: a code is printed on a noisy image and has to be typed back. Your own question: the admin sets a question and answer options, and the person picks the right one, which lets you check that they know the chat's topic or have read its terms.

The captcha type can be changed in the settings at any time. The correct answer is never sent to the person's device, only the images are, so it cannot be read from the page code.

Pictures are the easiest for people on a phone and do not depend on language. Letters feel familiar to anyone who has seen captchas on websites. Your own question suits closed and niche communities: an alumni chat can ask for the graduation year, a developers' chat can ask something only a person from the field would know.

Chat rules before joining

The admin writes the rules text: an age limit, no swearing or ads, the topic, anything else. It is shown in the check window above the task, and the agreement checkbox is required. The /rules command in the group shows the same rules to members who have already joined.

Two extra conditions can be turned on. “Telegram Premium only” lets in Premium users only. “Block new accounts” declines requests from recently created accounts; the age is estimated roughly, from the account id.

Group moderation — filters, welcome and commands

In a group @catalogue_app also moderates. The link filter and the swearing filter delete a regular member's message and issue a warning; after three warnings the member is muted for 24 hours. Admins' messages are not filtered. A welcome message greets new members with your text, and {name} inserts their name.

Admins manage members by replying to a message: /ban blocks, /unban unblocks, /kick removes without a ban, /mute 1h stops someone writing for an hour (other durations work too), /unmute restores it, /warn issues a warning.

Free and without a separate bot

The captcha lives inside @catalogue_app, so there is no bot of your own to create and nothing to sign up for. Everything is set up with buttons in a private chat with @catalogue_app. It works for groups and channels and costs nothing.

The captcha and moderation are set up per chat: one can use pictures and the link filter, another your own question and Premium only. The same rules text serves both the check window and the /rules command, so there is no need to write it twice.

How to launch

1. Open the link t.me/catalogue_app?start=captcha.
2. Pick your group or channel with the button, and @catalogue_app becomes its admin.
3. In the chat settings, turn on join requests and choose @catalogue_app as the bot that checks them.
4. In the chat with @catalogue_app, choose the captcha type and write your rules.
5. Optionally turn on “Premium only”, “Block new accounts”, the filters and the welcome message.

FAQ

Updated 01.11.2026