A rate limit caps how often an account may do something in a time window: so many follows per hour, so many DMs per day. Platforms run them everywhere and publish none of them. They're the first line of defence against automation, drawn at the speed of a plausible human.
Limits adapt to the account: age, standing and history move the ceilings, so a fresh account hits walls an aged one never feels.
Exceeding a limit escalates predictably: actions silently fail, then temporary blocks land (Instagram's action block is the famous face of this), then the account's standing degrades, which lowers the ceilings further. It's a spiral by design.
Rate limits meter what your account DOES. Deliveries to your public handle arrive at your account and spend none of its action budget: nothing logs in, nothing acts as you.
That's the structural reason delivery-based growth sits in a different risk category from automation-based growth, and why the first question about any service is whether it wants your password. See the mother/child scheme for what the other answer looks like.
Unpublished, adaptive, and different per account. Every exact number circulating is folklore. The observable rule: young accounts have low ceilings, and bursts trip them fastest.
Heavy normal use can brush them (mass-liking a friend's grid, follow sprees at events). The limits price behaviour patterns, not intentions.
Platform-side ingestion has its own pacing, which is one reason drip feed delivery exists. Your account's own action limits aren't touched by deliveries.
Related terms
Every definition lives in the full glossary, and the services behind the vocabulary are on the services page.