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I am building an application which requires user to paste the transaction hash of a transaction. But i want a regex string i could pass to the pattern attribute of the input element that receives it to validate it. What is the general regexp that validates ethereum transaction hash?

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  • Possible duplicate of How can I check if an Ethereum address is valid? – Richard Horrocks Dec 24 '17 at 14:13
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    @RichardHorrocks It's not a duplicate; this question is about the transaction hash, not the address. I don't see a regex for the transaction hash in that answer. – Jesbus Dec 24 '17 at 14:16
  • Ah, sorry, you're right :-) I read "regex" and ignored everything else :-) Removed duplicate vote. – Richard Horrocks Dec 24 '17 at 14:18
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This regex should do the trick:

/^0x([A-Fa-f0-9]{64})$/

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  • Keep in mind this only validates if the search contains only the right characters in the right length, not if a transaction exists on the blockchain. – Nick Dec 24 '17 at 17:38
  • @Nick this is clear. Thats just what i want – Oluwatumbi Dec 25 '17 at 15:04
  • I accepted the answer but i will rather go for /^(0x)?([A-Fa-f0-9]{64})$/ because it is also valid incase the source is from some of those who don't include the 0x prefix. Or do you think that should be considered invalid? The API i use to query the transactions accepts transaction IDs without the 0x – Oluwatumbi Dec 25 '17 at 15:06
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As you didn't specify the technology you are using, I would suggest validating it against the go-ethereum hexutil https://github.com/ethereum/go-ethereum/blob/master/common/hexutil/hexutil.go#L60

Here's a simple example written in golang:

// IsValid : validates transaction with go-ethereum utils
func (model *Transaction) IsValid() bool {
    _, err := hexutil.Decode(model.Hash)
    return err == nil
}
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