What are decentralized cryptocurrency exchange?

Decentralized Exchanges shortly termed as DEX supports cryptocurrency trading between buyer and seller without the involvement of the admin. DEX platform is built with smart contracts which act as admin which controls and processes all the transactions automatically. This new form of crypto trading is also accepted by a wide range of crypto users, apart from its liquidity issues. Many decentralized exchanges face liquidity issues which makes it less adaptable by crypto traders. You can launch your own decentralized exchange platform with low or no liquidity problems through the decentralized exchange script developed and deployed at Bitdeal.

Short answer for main difference betveen CEX and DEX (source: hackernoon)