Scalping is a trading strategy, which allows traders to make profit off small price changes, opening and closing many trades quickly. Scalpers usually place anywhere between 10 and a few hundred trades in a single day. The profit of each trade would be small, hence the big number of transactions.
The thing with scalping is that it's a practice often frowned upon by brokers, and especially market makers. Here is why.
When we open positions, market makers hedge these positions against other traders, or simply pass them on to the interbank markets. During slow markets and low volatility, the broker would wait some time (maybe 1, 2, or even 5 minutes) and if no other traders matches our position, they would pass it on to the interbank market. If we close the position before it is matched or passed on, the broker loses money. While this is not exactly fair play, many brokers practice it, and this is why they are against scalping.
Another thing that you should keep in mind is that the definition of scalping varies from broker to broker (some qualify any position kept open for 2 minutes or less scalping, for other brokerages this time is 5 minutes and so on).
Below is a list of brokers that officially allow scalping.
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|$5||1:500||1||20% Bonus||Review Website|
|$500||1:200||2.8||30% - 50% bonus||Review|