Poloniex exchange is one of the major and recognized crypto/fiat base exchange platform that have been operating since 2014 I've been using these exchange for couple of months now, I would say base on my experience the platform is very transparent and credible for use.
Users around the world can access the exchange from mobile device which is compatible with both android and ISO device Interestinly users can also perform their basic trading activities from browser which gives the impression that Poloniex is very scalable and flexible with software apps and browsers.
Although the exchange have been prone to online theft where users fund were move despite all these the exchange have stood out among major recommended exchange platforms today, it support two factor authentication system with API key users privacy and account are highly out into consideration.
Basically Poloniex is a crypto to crypto base exchange with new advancement the platform in 2019 support fiat currency exchange in which users can exchange both fiat and crypto currency the platform support multiple crypto pairs which can be traded, Interestinly unlike other exchange platform Poloniex have technical analysis tools for users to conveniently make market analysis.
Transaction on Poloniex is very fast with low transaction fee when making transaction among users.
In general there have been much advance improvement on Poloniex which have attracted lot of investors it's a credible exchange for investors and traders.