TBB Speed Test vs BT Speed Test

I have FTTP BT 900.
Until recently, when testing with TBB I consistently got 904 to 907 Mbps down and 90 to 92 Mbps up.
In the past when the readings were slow a reboot of the router invariably fixed that.
Lately (last few days) I get between 670 to 760 down but up remains at 90 to 92. Rebooting does not fix that.
However BT test says I get 947 down and 111 up and it never changes which I find suspect.!
Has the TBB test been changed in any way?
Which test should I believe?
Is there any independent from BT method that can verify their figures?
Thanks.

In reply to a post by Rytenuff:

Which test should I believe?
Is there any independent from BT method that can verify their figures?

Believe both tests, they are testing slightly different things.

Since no one company controls ‘The internet’ the speedtest from BT goes direct over their network to your home (as you buy internet access from BT) and so you get the best speeds.

Testing from Thinkbroadband or from any other non-BT network speed tester has to cross various connection points, any of which can be subject to congestion. If you tried Broadband Reports (in the US) for example then speeds would be a lot lower.

Depends what you are testing to prove…?

The site https://fast.com is hosted by Netflix so that people can test they have sufficient speed to watch video streams in high quality.

Step 1: Don't speed test unless the service isn't performing to expectations when you're actually using it.
Step 2: If it genuinely seems slow try using the app available at https://speedtest.net
Step 3: https://fast.com

I speed test to see if the service I am paying for is still the service I am paying for.
As I wrote TBB has been consistent for 18 months and was within 3% of the BT speeds tests. There is now a 22% drop in the reported speeds between TBB and BT tests.
Fast.com is never consistent but was close to TBB speeds though sometimes it would report a speed of 1.1Gb!

The point I am trying to make is that TBB has been consistent for at least 18 months and has been in near agreement with BT's tests within 3%.during this time.
The tests now at any time of day or night is closer to 22% different. This is a considerable deviation from the previous experience and leads me to question whether BT are throttling the connection in some manner or that TBB may have altered their test somewhat.
Fast.com is too inconsistent to rely on.
If it was possible to post my record of TBB tests it would be immediately apparent to anyone what I am highlighting.

In reply to a post by Rytenuff:

If it was possible to post my record of TBB tests it would be immediately apparent to anyone what I am highlighting.

You can create a logon on the main site (not forum) and the tests are logged.

But you can’t expect the internet to never change; speedtests from outside the BT network into BT are likely to change all the time. There are no speed guarantees on the internet.

In reply to a post by Rytenuff:

I speed test to see if the service I am paying for is still the service I am paying for.

Whatever makes you happy.

See https://www.novoserve.com/speedtest and download iPerf3 to use with it for the gold standard in speed testing.

In reply to a post by jchamier:

In reply to a post by Rytenuff:

If it was possible to post my record of TBB tests it would be immediately apparent to anyone what I am highlighting.

You can create a logon on the main site (not forum) and the tests are logged.

But you can’t expect the internet to never change; speedtests from outside the BT network into BT are likely to change all the time. There are no speed guarantees on the internet.

I know that. It's not as if I am completely new to broadband and the internet. I'm sure you don't mean to be condescending? I have registered on Thinkbroadband and logged on and have for several years It is these consistent saved TBB records since I got FTTP 900 that I am referring to! 18months of them at over 900 Mbps and a sudden drop to 660 /760 ish. I can't make this any clearer. Something has changed....I'm none the wiser.....but thanks for your help.

One or more of the upstream connections is causing the TBB speed test to be slower - it is possible the route from BT to TBB for your connection has changed and therefore you are currently on a different path to TBB. However, your speed to other servers on the Internet may be unaffected. BT are charging you for a connection to the Internet - they can't guarantee anything beyond that. It is quite possible that the path will change again and your speeds may go up or down to TBB - but you might find that speeds reducing on this path to TBB may have increased to other sites on the Internet.

The BT test proves that your link to BT is running at full speed (or at least mostly proves it - even those tests aren't 100% proof). It is possible that the slower speed is due to the uplink from BT to the Internet but you would need more than just TBB speed tests to show that it is a general issue with the uplink. Anything beyond that BT controlled uplink is not BTs responsibility and therefore not within their power to change.

Thank you. .