macOS has a shortcut for this, and it works well one paste at a time. Here is how to use it, what it leaves behind, and what PlainType does differently.
⌥⇧⌘V
Option-Shift-Command-V · Edit › Paste and Match Style
Press ⌥⇧⌘V instead of ⌘V. The pasted text takes on the style of the text around it instead of bringing its own fonts, sizes, and colors. In apps that support it, the same command is in the Edit menu as Paste and Match Style.
Where it stops:
For a longer block of text, paste it into a new TextEdit document, choose Format › Make Plain Text, then copy it again. The document loses all text styles and formatting. The same limit applies: the characters themselves don't change.
PlainType cleans text when you copy it, not when you paste it. With Auto-clean on copy turned on, it watches for rich text on the clipboard and writes back a cleaner plain-text version. After that, a regular ⌘V pastes clean text in any app.
If you paste formatted text now and then, into apps that have Paste and Match Style, ⌥⇧⌘V is enough. If you paste into notes, docs, chat, email, and task trackers all day, or you need straight quotes and no leftover Markdown, cleaning once at copy time saves the extra step on every paste.
PlainType is a native Mac app for macOS 14 Sonoma or later. See how it works.
Related: Remove smart quotes and clean up copied text