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InstaSwap is a non-custodial cryptocurrency exchange. It allows buying, selling, and swapping cryptocurrencies. The platform is launched by Blocktech Private Company which is registered with Hellenic Capital Markets Commission. This registration is a sign telling us that the company is legit and is subjected to thorough audits. InstaSwap is available for use in the US.
GBX Digital Asset Exchange is registered in Estonia offering crypto trading and fiat onboarding opportunities. GSX group unites several companies, including the Gibraltar Stock Exchange. 
XT.com is a centralized cryptocurrency exchange set in 2018 in Hong Kong. Available markets are: BTC, SXC, USDS, XT.