O3 has released a new UTXO manager feature that is intended to help Ledger users to consolidate UTXOs (unspent transaction outputs). This is designed to address the “Transaction is too big to sign” error that may occur when trying to sign a NEO or GAS transaction with a Ledger device.

On the current NEO platform, the NEO and GAS assets are unique in that they use the UTXO model first popularized by Bitcoin. Unlike NEP-5 transfers, UTXO transfers require the unspent outputs to be calculated before the outbound transaction can be sent.

Due to the limited memory capacity of Ledger devices, such as the Nano S, having too many UTXOs can cause the transaction to fail due to the Ledger running out of memory. This can be visualized as adding up pocket change to make a purchase; the more small change is being processed, the more calculation must be done before the total is determined.

The UTXO manager allows a user to connect with their O3 wallet, which will then display all UTXOs for the NEO and GAS assets. The user may then use the ‘Send’ button to combine these outputs by sending them back to their own address. Following this process, the Ledger device should again be able to sign transactions.


If the Ledger cannot process all of the listed UTXOs in one instance, the user may specify a lower number to combine until the Ledger is able to sign the transaction.