IQOption
Questions & Answers

Two things: regulation and reputation.
Both are easy to check. Regulation information is available on the website. While for reputation check reviews and history. Tip: the broker is with proven track record for a decade, this itself is proof of its reliability

Check execution during periods of high volatility, how well they handle slippage and whether they process your orders on quotes you asked. And of course test withdrawals. With deposits you will never have problems, but a true broker is always determined by withdrawals. If they send your requests to payment providers fast, it means they’re ok.