Fulcrum: A fast & nimble SPV server for Bitcoin Cash, Bitcoin BTC and Litecoin.

[chmod755]

Hey guys,

Fulcrum SPV server now has an awesome website (90s style  ) https://fulcrumserver.org/

If you're operating Fulcrum: Is there any information that should be added to this page?

If you have wishes for features or if you want support for an additional cryptocurrency you can contact the dev and he's certainly open to prioritize requests if there is some incentive (donations).

[DaveF]

The link to the only releases you should download are: https://github.com/cculianu/Fulcrum/releases
Don't know if that site is legit or not at the moment. The developer has not mentioned it on his github page: https://github.com/cculianu/Fulcrum?tab=readme-ov-file

A link discussing it here: https://bitcointalk.org/index.php?topic=5441463.0

I did run it for a while and it does work well. But with all the other nodes I have, running a dedicated machine for just that just seemed like a waste. Will probably spin another one up sooner or later to see if anything has changed.

-Dave

[chmod755]

The link to the only releases you should download are: https://github.com/cculianu/Fulcrum/releases
The developer has not mentioned it

That is true. Note, that this website does not host binaries!

Edit: It is now referenced on GitHub https://github.com/cculianu/Fulcrum/blob/master/README.md

[Cricktor]

I've been using Fulcrum as my personal Electrum server for quite some time and am very happy with its speed compared to electrs.

Just recently I upgraded from version 1.12 to the new version 2 which required a complete new sync. While Fulcrum is faster than electrs to deliver queries of a SPV wallet, it does sync considerably slower than electrs. But as the author of Fulcrum claims that version 2 has better database atomicity and much better resilience to potential database corruption issues, it was a no-brainer for me to upgrade.

I'm running a Bitcoin Core full node and the Fulcrum Electrum server in containers managed by Umbrel in a Virtualbox VM running on a PC host in Linux Mint. It's an old  Dell Latitude E7470 laptop and I gave this VM about 24GiB RAM as I'm running and testing out other containers therein, too.

The Bitcoin Core node was already synced and Fulcrum took around 8 days and a few additional hours to sync fully, see fragments of the Fulcrum log below. I'll make a backup of the synced Fulcrum to avoid these 8 days of syncing if something should break in the future.

Timestamps are in UTC; syncing Fulcrum was interrupted one time around the middle of total blocks to tweak a few settings in the hopes to speed up the process a little bit which is why it logged "... Processed 411320 new blocks ...":

Code:

[2025-11-11 13:51:33.434] <Controller> Block height 923156, downloading new blocks ...
[2025-11-11 13:51:35.313] <Controller> Processed height: 1000, 0.1%, 532.7 blocks/sec, 542.8 txs/sec, 556.7 addrs/sec
[2025-11-11 13:51:37.453] <Controller> Processed height: 2000, 0.2%, 467.3 blocks/sec, 472.4 txs/sec, 509.3 addrs/sec
[2025-11-11 13:51:38.701] <Controller> Processed height: 3000, 0.3%, 801.3 blocks/sec, 817.3 txs/sec, 848.6 addrs/sec
[2025-11-11 13:51:40.621] <Controller> Processed height: 4000, 0.4%, 520.8 blocks/sec, 525.0 txs/sec, 567.7 addrs/sec
[2025-11-11 13:51:42.305] <Controller> Processed height: 5000, 0.5%, 594.2 blocks/sec, 597.1 txs/sec, 632.2 addrs/sec
...
[2025-11-19 18:42:12.075] <Controller> Processed height: 921000, 99.7%, 49.4 blocks/min, 2613.4 txs/sec, 5650.8 addrs/sec
[2025-11-19 19:02:25.519] <Controller> Processed height: 922000, 99.9%, 49.4 blocks/min, 2592.3 txs/sec, 6183.7 addrs/sec
[2025-11-19 19:24:09.131] <Controller> Processed height: 923000, 100.0%, 46.0 blocks/min, 2360.5 txs/sec, 6394.7 addrs/sec
[2025-11-19 19:30:18.984] <Controller> Processed 411320 new blocks with 966985169 txs (2409218915 inputs, 2689487530 outputs, 3490612954 addresses), verified ok.
[2025-11-19 19:30:18.997] <Controller> Block height 924329, downloading new blocks ...
[2025-11-19 19:43:39.594] <Controller> Processed height: 924000, 100.0%, 49.1 blocks/min, 2816.1 txs/sec, 6166.9 addrs/sec
[2025-11-19 19:52:42.567] <Controller> Processed 984 new blocks with 3121169 txs (7030325 inputs, 8593806 outputs, 7890681 addresses), verified ok.
[2025-11-19 19:52:42.614] <Controller> Block height 924330, downloading new blocks ...
[2025-11-19 19:52:44.177] <Controller> Processed 1 new block with 3962 txs (6725 inputs, 13334 outputs, 15360 addresses), verified ok.
[2025-11-19 19:52:44.179] <Controller> Block height 924330, up-to-date
[2025-11-19 19:52:44.185] SrvMgr: starting 2 services ...
[2025-11-19 19:52:44.211] Starting listener service for TcpSrv 0.0.0.0:50002 ...
[2025-11-19 19:52:44.221] Service started, listening for connections on 0.0.0.0:50002
[2025-11-19 19:52:44.221] Starting listener service for AdminSrv 0.0.0.0:8000 ...
[2025-11-19 19:52:44.235] Service started, listening for connections on 0.0.0.0:8000
[2025-11-19 19:52:44.236] <Controller> Starting ZMQ Notifier (hashblock) ...
...

[zabzob]

Just recently I upgraded from version 1.12 to the new version 2 which required a complete new sync.

Thanks for this update. I'm planning on setting up my own Fulcrum server soon, so I look forward to hearing how it goes with the new version.

[Cricktor]

My one or two Electrum wallets that I use regularly work just fine with Fulcrum. I didn't notice any difference to the prior version of Fulcrum. They open almost instantly. (Those two Electrum wallets aren't particularly large, meaning they don't have a large transaction history or have lots of addresses being used.)

At the moment I'm not going to test and evaluate how resilient Fulcrum v2 is regarding database corruption. I can't remember to have had an issue with corruption with Fulcrum 1.x before. My old Fulcrum always opened its databases happily without complaining, but I paid attention to not kill any Fulcrum process ungracefully.

I had maybe only very few unexpected container restarts with the old version and it didn't feel comfortable to hope that Fulcrum's databases won't become corrupted. I just leave it running 24/7 because the Bitcoin Core node runs 24/7, too.


Later edit:
Fulcrum v2 can also serve large address histories without choking. E.g. it synced a test watch-only Electrum wallet of the P2PKH legacy address representation of the Genesis block (1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa). My test wallet synced to 54,274 transactions for this legacy address as of 2025-11-22 ~17:00 UTC. This took some time but finished without errors (needs a bit of tweaking both for Fulcrum Server and Electrum 4.6.2 to accept large address history responses).