Slippage is the difference in price that can occur between the time a trade order passes and its actual execution.
It can occur at any moment, but it is most common during periods of higher market volatility or during important Forex news announcements.
According to market execution, slippage can be a both positive and a negative. This means that there was a strong jump in quotations. Every broker has its own liquidity providers and different terms of trading with them. That's why there is a difference in price quotes, which also appears on the charts. It can be up or down, different lows and highs, open and close, etc. Each broker receives a unique stream of price quotes from liquidity providers, due to which brokers will have price differences.
In addition, we offer market execution, where all orders are sent to the market for execution and are executed at the current market price. This price can be different from the one requested by the client and the difference is called slippage. From our internal order execution statistics we can historically see that more than 50% of all trades are executed "at price", without slippage, while around 25% (may differ per single instrument) are executed with a better price for you (positive slippage) and around 25% with negative slippage.