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Proof Comcast Throttling Internet Speeds

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Proof Comcast Throttling Internet Speeds

Comcast Throttling Speeds Proof

The History

My internet speed for the 6 months has been on average 5 Mbps download 24 Mbps upload. It looks like Comcast is throttling my speeds and trying to do so without being noticed. When I run a speed test using Comcast speed test I get 150 Mbps but when I use any other speed test service the max I am getting is between 5 Mbps and 20 Mbps. All of my streaming videos are not working, and my downloads are delayed. Right now, I am downloading a 1 GB file and it is taking over 40 minutes. This is not a temporary outage as it has been like this for the last 6 months, and it doesn't look like a connection issue as my upload speeds are fine.


Speed Test Proof Of Comcast Speed Throttling

Why am I paying for 150 Mbps internet when most of the time my speeds are under 20 Mbps? There have been multiple service calls, chat supports, home visits, etc. for this is issue and it still is not resolved. Why you ask, well I don’t have TV service and stream my media. It is clear by the speed tests what is happening. Comcast is making sure their speed test service and Ookla's speed test are not throttled so it is not noticeable. When I run a speed test using other devices (PS4, FireTV, etc.) or other speed test services (Google,, etc.) I never am getting more than 20 Mbps.


Speed tests on servers not owned by comcast:


Comcast Throttling Speeds.PNG

Down: 22.9

Up: 19.8



Down: 15.2

Up: 23.8

Down: 10.77

Up: 25.77

Down: 6.03

Up: 22.29

Down: 3.7

Up: 16.7

Down: 13.7


As you can see there is some variation between the less common speed test servers but not much they are all in a +-19 Mbps range.  These tests were running one after another. Another interesting thing to note is the speeds get slower and slower. Why is this interesting? Well if you don’t stream video or download large files like 50% of the us you would never notice this as your occasional YouTube video or small file download would at fast speed. This throttling is specifically target at those who stream a lot of large size media (1080p and 4k movies and tv). Whereby the speed progressively gets slower and slower until the media no longer plays and must buffer.

Comcast Throttling Speeds Proof.PNG

<Edited for inflammatory remarks>.


Comcast Faking Speeds With

Now look when using comcasts speed test or Ookla( (owned by Comcast and using comcasts speed test server)

up: 147.75

down: 22.96

down: 103.79

up: 24.16


Comcast Speed Throttling Proof Conclusion

Hmm, speeds are much faster by a huge variation for comcast owned speed tests. Also, these are the tests customer service agents are trained to tell customers to use then they complain of slow speeds. Coincidence? I think not.



So if any comcast reps ever read this, my challenge is to prove me wrong. Have my speeds that I PAY FOR be what they are supposed to be consistently.










Re: Proof Comcast Throttling Internet Speeds

Honestly, much of it may just be resource-limited comcast DNS and caching servers. If you're running your own modem/router I'd try changing the DNS to google's or openDNS as a troubleshooting step.

New Poster

Re: Proof Comcast Throttling Internet Speeds

Sorry, but no.
First let's explain why your assumption is based on nothing.

DNS: DNS is a service that translates domain names into IP addresses. Without it, everyone would need to know the IP address of any given connection on the internet. Your statement that the connection speed issue this user is suffering is a "resource-limited comcast DNS and caching servers" Makes absolutely NO sense, and here's why.

When you connect to the speed test servers, the Comcast DNS servers pulls up the DNS records for that domain, and trasmits that to your computer. Your computer caches that DNS result. Essentially meaning, once you've pulled up the site, your computer knows the IP address of that domain.  Once you begin the speed test, the applet on the website sends a packet stream to your computer, at no point in time is comcast's DNS services utelized after the innitial handshake of this transmission. Meaning, that once the first few packets are sent, comcasts DNS servers no longer play a role in the transfer. What does play a role in the rest of the transfer, is comcasts switching and routing hardware and software.

If as you say, it is a resource issue, then comcasts own speed test applet would suffer the same issues, as it's run on the same hardware. Unless of coarse it's being run on special, or significantly different hardware than what is typically used. Ergo, unles they are intentionally cheating the test.

You next make the assumption that changing the DNS settings of a personal modem / router would help. This also is not the case, if they were at fault, than comcasts own speed test would show similar results as the others, but since it does not, this rules out DNS issues at the intermediary equipment such as a home router / modem. 
Regardless of the DNS settings your PC, or Router has, Comcasts own DNS records, and hardware are how your connection is established to the network. If they were at fault, your connection wouldn't even be possible.

What this user's experience is highlighting, is the intentional misrepresentation of connection speeds by comcast, by way of focusing on their own speed test, which has a proven track record of falsifying speeds it reports for comcast customers..

That all being said, there are also other factors to consider. Namely, the response time of any hops being made int he network rout to each speed test. With the comcast test, this isn't going to be realistic, as it's going to be at maximum, a 4 node rout, 3 of which will be internal routs on comcasts own network.

So unless every other speed test mentioned is suffering from a partuclarly poor set of nodes, the inference would remain that comcast is intentially throttling, or otherwise shaping the datastream to nodes outside of their own network.


Re: Proof Comcast Throttling Internet Speeds

If Comcast were throttling internet speeds as you suggest, then why are my speed tests uniformly about the same? I did these tests just now, 6:45 PM PDT, when everyone's home and streaming -


Comcast: (Netflix's site)


and finally, DSL Reports (probably the most accurate one out there)


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Re: Proof Comcast Throttling Internet Speeds

Not sure what's going on with your connection.. Doing those tests with wifi?


I just ran the same tests as you did, my results are different.. if Comcast were throttling, why you and not me? I don't know where y'all are getting the idea that you're being throttled on purpose. That is something I have never seen.


Anyway, my results:

2018-03-13 09_34_47-Speakeasy Internet Speed Test - Check Your Broadband Speed _ MegaPath.jpgSpeakeasy


2018-03-13 09_35_45-speed test - Google Search.jpgGoogle


2018-03-13 09_37_17-Broadband Internet Speed Test by Verizon _ Official Site.jpgVerizon


2018-03-13 09_38_18-SpeedOf.Me, Internet speed test for all your devices _ Non Flash_Java Broadband.jpgSpeedOF.Me


2018-03-13 09_41_17-Internet Health Test.jpgInternet Health Test


2018-03-13 09_46_56-Speedtest by Ookla - The Global Broadband Speed


2018-03-13 09_48_11-XFINITY Speed Test.jpgXfinity



Those results are consistent with my SamKnows testing (30 day charts):

2018-03-13 09_51_16-Download - 09_51_48-Upload -

New Poster

Re: Proof Comcast Throttling Internet Speeds

I just had the same problem. I disconnected my wireless router and did the speed tests with ookla then xfinity. The difference was 60 mbps higher on the xfinity site. What I can tell you is that the xfinity reading was inaccurate. There is no chance I was getting the 80 mbps speeds it was saying. I was having trouble loading regular web pages. 


I can't come up with a logical reason for why xfinity's site would give you faster test results other than the obvious: comcast is lying. 


I honestly think they randomly throttle people's internet then when you call they try to upsell you for faster service. No, I wouldn't put it past them. 


Re: Proof Comcast Throttling Internet Speeds

@alphawave wrote:

I can't come up with a logical reason for why xfinity's site would give you faster test results other than the obvious: comcast is lying. 

The reason that their *in house" speed tests show faster speed is because their speed testing servers lie on *their* network's edge, therefore they are not subject to any third party's potential backbone deficiencies / routing deficiencies / distance related latency issues etc.

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New Poster

Re: Proof Comcast Throttling Internet Speeds

I suspect the same thing with my connection. When I watch iTunes movies they will stall. I didn’t have this issue until the changes at the FCC. I suspect the change in leadership there has given service providers a blank check to make heir services and partners more appealing. It may a be a coincidence but it’s just too strange. The other option is it’s incompotence which isn’t much better.