# Release 3.1 - (March 5, 2018)
* Memory-pool based fee estimation. Dynamic fees can target a desired
depth in the memory pool. This feature is optional, and ETA-based
estimates from Bitcoin Core are still available. Note that miners
could exploit this feature, if they conspired and filled the memory
pool with expensive transactions that never get mined. However,
since the Electrum client already trusts an Electrum server with
fee estimates, activating this feature does not introduce any new
vulnerability. In addition, the client uses a hard threshold to
protect itself from servers sending excessive fee estimates. In
practice, ETA-based estimates have resulted in sticky fees, and
caused many users to overpay for transactions. Advanced users tend
to visit (and trust) websites that display memory-pool data in
order to set their fees.
* Capital gains: For each outgoing transaction, the difference
between the acquisition and liquidation prices of outgoing coins is
displayed in the wallet history. By default, historical exchange
rates are used to compute acquisition and liquidation prices. These
values can also be entered manually, in order to match the actual
price realized by the user. The order of liquidation of coins is
the natural order defined by the blockchain; this results in
capital gain values that are invariant to changes in the set of
addresses that are in the wallet. Any other ordering strategy (such
as FIFO, LIFO) would result in capital gain values that depend on
the presence of other addresses in the wallet.
* Local transactions: Transactions can be saved in the wallet without
being broadcast. The inputs of local transactions are considered as
spent, and their change outputs can be re-used in subsequent
transactions. This can be combined with cold storage, in order to
create several transactions before broadcasting them. Outgoing
transactions that have been removed from the memory pool are also
saved in the wallet, and can be broadcast again.
* Checkpoints: The initial download of a headers file was replaced
with hardcoded checkpoints. The wallet uses one checkpoint per
retargeting period. The headers for a retargeting period are
downloaded only if transactions need to be verified in this period.
* The 'privacy' and 'priority' coin selection policies have been
merged into one. Previously, the 'privacy' policy has been unusable
because it was was not prioritizing confirmed coins. The new policy
is similar to 'privacy', except that it de-prioritizes addresses
that have unconfirmed coins.
* The 'Send' tab of the Qt GUI displays how transaction fees are
computed from transaction size.
* The wallet history can be filtered by time interval.
* Replace-by-fee is enabled by default. Note that this might cause
some issues with wallets that do not display RBF transactions until
they are confirmed.
* Watching-only wallets and hardware wallets can be encrypted.
* Semi-automated crash reporting
* The SSL checkbox option was removed from the GUI.
* The Trezor T hardware wallet is now supported.
* BIP84: native segwit p2wpkh scripts for bip39 seeds and hardware
wallets can now be created when specifying a BIP84 derivation
path. This is usable with Trezor and Ledger.
* Windows: the binaries now include ZBar, and QR code scanning should work.
* The Wallet Import Format (WIF) for private keys that was extended in 3.0
is changed. Keys in the previous format can be imported, compatibility
is maintained. Newly exported keys will be serialized as
"script_type:original_wif_format_key".
* BIP32 master keys for testnet once again have different version bytes than
on mainnet. For the mainnet prefixes {x,y,Y,z,Z}|{pub,prv}, the
corresponding testnet prefixes are {t,u,U,v,V}|{pub,prv}.
More details and exact version bytes are specified at:
https://github.com/spesmilo/electrum-docs/blob/master/xpub_version_bytes.rst Note that due to this change, testnet wallet files created with previous
versions of Electrum must be considered broken, and they need to be
recreated from seed words.
* A new version of the Electrum protocol is required by the client
(version 1.2). Servers using older versions of the protocol will
not be displayed in the GUI.
