In addition to all the ethers.providers.* being moved to ethers.*, the biggest change developers need to keep in mind is that Web3Provider (which historically was used to wrap link-web3 providers) is now called BrowserProvider which is designed to wrap EIP-1193 providers, which is the standard that both modern Web3.js and injected providers offer.
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Method for broadcasting transactions to the network has changed
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The StaticJsonRpcProvider in v5 is now integrated into the v6 JsonRpcProvider directly. When connecting to a network which cannot change its network, it is much more efficient to disable the automatic safety check ethers performs.
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Since the fees for Ethereum chains has become more complicated, all Fee parameters in v6 were coalesced into a single .getFeeData method. While gasPrice is no longer widely used in modern networks, when using a legacy network, it is available using that method.
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