Bitcoin Core can't calculate the number of blocks left until it fetches all the block headers. Which it seems to have already done.
In my opinion, as long as the progress is continuously increasing, it means the node is syncing fine and that you don't have to worry about the lack of an ETA.
The last block time becoming more and more recent is also normal.
Topic: Number of blocks left: Unknown - should I worry? (Read 116 times)
For (possibly future) info, this was happening on an HDD.
How much RAM do you have? Syncing Bitcoin Core only gets slower due to the growth of your chainstate directory. I've done it on HDD with 32 GB RAM, and that's doable. But with 8 GB RAM and SSD, the SSD is already the limitation. If you're low on RAM and use HDD, you may want to reconsider and use Electrum instead. Or upgrade your PC.today, since I started the program, it only says "Unknown. Syncing Headers (870924, 100.0%)..."
This was probably some connection issues because your node should be able to quickly figure out how many blocks there are to download.
It's been years since I tried, but I remember starting Bitcoin Core with chainstate on HDD took minutes of looking at a "frozen" window. There is no "quickly". 
In past times, it reported a figure in "Number of blocks left", but today, since I started the program, it only says "Unknown. Syncing Headers (870924, 100.0%)..."
-snip-
I am not sure if I should be worried because the tool apparently does not know anymore the number of blocks left - or if this is somewhat normal at times?
If unsure, you can always count on the logs.-snip-
I am not sure if I should be worried because the tool apparently does not know anymore the number of blocks left - or if this is somewhat normal at times?
To check it, open your bitcoin data directory and find debug.log file, open it as a text file and look for related lines or errors.
If there's at least one, report it here together with your settings so we can suggest a solution.
Thanks for the quick reply.
Just as I wanted to open the cli, the program started to report the number of blocks left as I had known it - so everything seems good now.
For (possibly future) info, this was happening on an HDD.
This was probably some connection issues because your node should be able to quickly figure out how many blocks there are to download. It does that by first syncing its headers with the peers it connects to and the entire block headers file is only 66 MB and if your node has been running before, the data it needs to download is even smaller (80 byte per block, so 1 day worth of block headers is 11-12 KB).Just as I wanted to open the cli, the program started to report the number of blocks left as I had known it - so everything seems good now.
For (possibly future) info, this was happening on an HDD.
Meaning since the data is small, the only reason why your node would hang is if it couldn't connect or maybe the other peer was not responsive so it needed to time-out and connect to another peer.
Since you mention Bitcoin-qt you might be using the old version of Bitcoin core?
Why not tell us the version of your bitcoin-qt? If you are using old version, I suggest to update it first to the most recent version and test it again if it would sync properly.
You can download the latest version from here https://bitcoincore.org/en/releases/28.0/
Make sure before performing to upgrade it to the latest version you have a copy of a backup wallet.dat to a safe place for future recovery if things are going bad after the update.
Why not tell us the version of your bitcoin-qt? If you are using old version, I suggest to update it first to the most recent version and test it again if it would sync properly.
You can download the latest version from here https://bitcoincore.org/en/releases/28.0/
Make sure before performing to upgrade it to the latest version you have a copy of a backup wallet.dat to a safe place for future recovery if things are going bad after the update.
Thanks for the quick reply.
Just as I wanted to open the cli, the program started to report the number of blocks left as I had known it - so everything seems good now.
For (possibly future) info, this was happening on an HDD.
Just as I wanted to open the cli, the program started to report the number of blocks left as I had known it - so everything seems good now.
For (possibly future) info, this was happening on an HDD.
Running bitcoin core on any OS will definitely catch up (sync) with the blockchain. So you are correct that that's what it does.
It looks like an issue with calculating the time that is required until fully synced. I wouldn't worry, considering that the number of blocks left keeps decreasing.
What hardware are you using? SSD or HDD?
Can you also post a screenshot or log of the output of the bitcoin-cli getblockchaininfo command?
It looks like an issue with calculating the time that is required until fully synced. I wouldn't worry, considering that the number of blocks left keeps decreasing.
What hardware are you using? SSD or HDD?
Can you also post a screenshot or log of the output of the bitcoin-cli getblockchaininfo command?
I am running bitcoin-qt on Linux to catch up the block chain (at least that's what I believe it does)
In past times, it reported a figure in "Number of blocks left", but today, since I started the program, it only says "Unknown. Syncing Headers (870924, 100.0%)..."
However, the value of "Last block time" increases, at the time of this writing it is "Tue Apr 4 13:00:54 2023".
It also reports the following values:
Progress 72.64%,
Progress increase per hour 0.28%
Estimated time left until synced: Unknown...
I am not sure if I should be worried because the tool apparently does not know anymore the number of blocks left - or if this is somewhat normal at times?
In past times, it reported a figure in "Number of blocks left", but today, since I started the program, it only says "Unknown. Syncing Headers (870924, 100.0%)..."
However, the value of "Last block time" increases, at the time of this writing it is "Tue Apr 4 13:00:54 2023".
It also reports the following values:
Progress 72.64%,
Progress increase per hour 0.28%
Estimated time left until synced: Unknown...
I am not sure if I should be worried because the tool apparently does not know anymore the number of blocks left - or if this is somewhat normal at times?
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