One rich clipboard, two representations
For iMessage, Signal and the normal Telegram composer, Pasteful writes semantic HTML and a readable plain-text fallback when the browser supports rich clipboard writes. The receiving app chooses which representation it accepts.
There is no honest guarantee that every mobile or desktop client preserves the same rich paste. The plain fallback therefore keeps list markers, paragraph breaks and explicit link destinations.
iMessage
Apple documents bold, italic, underline and strikethrough as native iMessage formatting. Pasteful converts headings into emphasized message lines and leaves unsupported document layout behind. Apple says formatted text becomes plain on older or non-Apple operating systems.
Signal
Signal documents bold, italic, strikethrough, monospace and spoilers through its selection menu and desktop shortcuts. Signal does not publish standard Markdown as the ordinary message paste format. Apply a spoiler in Signal because it is a native message feature, not generic rich text.
Telegram
The Pasteful destination targets a person pasting into Telegram's normal composer. Telegram Bot API MarkdownV2, HTML and rich messages are separate developer formats and need their own escaping, limits and payload validation.
Telegram's API also distinguishes visible text from message entities such as links, mentions, code, spoilers and quotations. A normal clipboard paste cannot safely invent account-bound entity IDs.
Paste it into Pasteful. It stays in this tab.