I want to use uint256_t in my EOS smart contract but I am getting following error

unknown type name 'uint256_t'; did you mean 'uint16_t'?

I thought EOS supports uint256_t as I read it in some EOS documentation. Unfortunately, I can't seem to find that piece of documentation again!

This Reddit link also says the uint256_t is supported! Did I miss something?

  • uint256_t is not actually defined in eosio. if you want a third party library for this see this
    – confused00
    Commented Nov 14, 2018 at 10:23

3 Answers 3


According to the documentation, you can use the uint256_t type, for instance, as secondary index of a multi index table. Here you can find an example (is commented).


uint256_t is not provided in eos, you may use boost::multiprecision to get a typedef for uint256_t


The ethereum virtual machine on EOSIO allows up to 1024 bit precision for integers and can be directly used in your smart contracts with not so much bloat: https://github.com/jafri/eosio.evm/tree/master/eosio.evm/external/intx

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