You’re mid-task, the tool stops, and a message appears saying you’ve reached your limit and can try again at 4pm. No warning that you were close. No number that would have let you pace yourself.
That’s a rate limit. Every AI service has them, and the reason they feel arbitrary is that they’re usually not counting the thing you assumed they were counting.
What it means
A rate limit is a cap on how much you can use a service inside a window of time. It exists because the chips these models run on are finite and shared, so without a cap one heavy user can slow the service down for everyone else. Consumer apps express the limit as messages or hours. Underneath, most of them are counting tokens (the chunks of text a model reads and writes), and the developer versions say so openly, in requests per minute and tokens per minute.
Why it matters
Long conversations burn through the cap much faster than short ones. Every time you send a message, the entire conversation so far goes back to the model, so your fortieth message in a thread costs many times what your first one did. Starting a fresh chat for a new topic isn’t tidiness. It’s rationing.
Not all limits stop you. Some services quietly move you to a smaller, faster model when you cross the line, so the answers keep coming and just get worse. If a tool seems dumber late in the day, that’s worth checking before you blame the model.
The caps are a business decision, not a law of physics, and they move. Vendors tighten them when demand spikes and loosen them when capacity comes online, usually with little notice. Any workflow that assumes you’ll get a certain amount of use per day is resting on something the vendor can change on a Tuesday.
Simple example
Your phone plan doesn’t cap how many times you pick up the phone. It caps gigabytes. Text all month and you’ll never come close. Stream a bunch of movies on the train and you’re most of the way through it.
Go over, and in most cases the phone doesn’t stop working. It gets slow. You spend the next day assuming the network is having a rough week, and nobody ever tells you otherwise.