Three words get used interchangeably and mean different things. Getting them straight saves you paying for the wrong tool.
A screener answers one question: which coins match this condition right now? You give it a rule — RSI below 30, MACD just crossed up, price at a 30-day high — and it checks every pair on the exchange and hands back the list that currently satisfies it. It is a filter over the whole market at a single moment in time.
That is the entire idea, and it is more useful than it sounds. Checking 500 charts by hand is not a thing anyone does. Checking one condition against 500 charts takes a computer a few seconds.
| Tool | Answers | Runs | Best for |
|---|---|---|---|
| Screener | Which coins match, right now? | When you ask | Building a shortlist to look at |
| Scanner | Same question — the words are used interchangeably | When you ask, or continuously | Same thing; "scanner" often implies it keeps running |
| Alert bot | Tell me when a coin starts matching | Continuously, in the background | Conditions you cannot sit and watch for |
| Trading bot | Match the condition, then place the order | Continuously | Automating execution, not selection |
In practice "screener" and "scanner" are the same tool under two names. The real distinction is the third row: an alert bot is a screener that never stops running and tells you when the answer changes. A trading bot is an alert bot that acts on it. Each layer adds capability and risk in equal measure.
A screener tells you a condition is true. It does not tell you what happens next, and any tool that claims otherwise is selling a forecast. A match is a starting point for your own analysis — a reason to open the chart, not a reason to open a position.
A screener that only knows about 50 large-cap coins cannot find you anything you would not have found anyway. The point of screening is reaching the part of the market you are not already watching. altscreenerai covers 500+ USDT perpetual pairs.
A condition on daily candles and the same condition on 15-minute candles are different signals with different lifespans. If you trade intraday, a screener limited to daily candles cannot see your setups at all. This is the single most common reason a free screener turns out to be unusable — check the timeframe list before anything else.