This article covers the restrictions and limits on file (document) uploads, message length and some blocks.
Files:
Maximum image resolution: 8 MP.
Maximum image size: 10 MB.
Maximum size of other files: 50 MB.
Maximum size of a file uploaded by a user that can later be downloaded or viewed: 20 MB.
Allowed image formats: image/bmp, image/gif, image/jpeg, image/png, image/x-ms-bmp.
Allowed video formats: video/quicktime, video/mp4, image/gif.
Allowed audio formats: audio/mpeg, audio/mp3, audio/x-wav, audio/x-m4a.
Timeout block:
Maximum timeout: 86400 sec (1 day).
Minimum timeout: 1 sec.
Characters:
Maximum message length in a text block: 4096 characters.
Maximum message length in media blocks: 1024 characters.
Maximum number of rows in a keyboard: 22.
Maximum number of buttons in a keyboard row: 12.
Maximum number of characters in a command name or payment name: 64.
Telegram limits
Bots:
Number of bots (created via @BotFather): up to 20.
Bot @username length: 5 to 32 characters.
Bot about text length: up to 120 characters.
Bot description length: up to 512 characters.
Number of buttons: up to 100.
Accounts:
Username (for example, @username): 5 to 32 characters, from 4 characters for NFT usernames.
Bio: 70 characters; 140 characters for Telegram Premium subscribers.
First name length: 1 to 64 characters.
Last name length: 0 to 64 characters.
Number of channels and supergroups you can be a member of: up to 500 (including the ones you created); up to 1000 for Telegram Premium subscribers.
Creating groups and channels: up to 50 per day.
Number of accounts (official clients): up to 3 profiles; 4 to 6 profiles for Telegram Premium subscribers (depends on the app).