I am writing a bot that gets channel usernames by provided channel ids. It does not get username by id

[Kenya-West]

Consider the following code to get channel username by provided id:

public startFlow(bot: Telegraf<any>): Promise<void> {
        bot.start((ctx) => ctx.reply('Welcome. I am a bot that retrieves usernames by Telegram ID. Send me Telegram ID and I will return the username'));
        bot.help((ctx) => ctx.reply('Send me a Telegram ID'));
        bot.on(message('text'), (ctx) => {
            try {
                const id = ctx.message.text;
                bot.telegram.getChat(id).then((chat) => {
                    ctx.reply(`Username: ${(chat.type === 'private' || chat.type === 'channel') ? chat.username : chat.title}`);
                }).catch((err) => {
                    ctx.reply('User not found');
                });
            } catch (err) {
                ctx.reply('Invalid data, ID, or format');
            }
        });

        return Promise.resolve();
    }

It always fails to get username as it receives 400 Bad request response:

Try it yourself with -1001051500113, 1001051500113, and 1051500113 - all are the ids of the same channel.
I am a subscribed to this channel, and the channel is public and has username.

Why does it happen?

[MKRhere]

Bots can only call getChat on chats they are a member of. Is your bot a member of the channel you are attempting to fetch?

[Kenya-West]

Thanks for clarification.

No, my bot was designed to get an info about any public chat, group or channel.

But since that is not possible via BotAPI, any workaround to retrieve publicly available information? Maybe by userbot (TDLib)?

[MKRhere]

Yes. You could try using something like https://github.com/gram-js/gramjs with a user account to fetch that information, then deliver it through your bot.