I subscribed to Netflix right after their global launch made the service available in India, but after a month or two of binge watching my favorite TV shows, streaming speed declined drastically. I don’t remember the last time I could watch a full episode or a movie without the video quality dropping mid way or playback getting stuck due to buffering.

I went crazy trying to diagnose the issue. First I blamed Netflix and their servers but several of my friends and colleagues told me they get uninterrupted streaming even on terrible internet connections. I then blamed my ISP and called them up half a dozen times, and they promptly blamed my router. One time their service guy came over, connected the LAN cable directly to my laptop, opened up 2 or 3 Ultra HD YouTube videos simultaneously in different browser tabs and all of them played fine. Speedtest.net showed fantastic speeds as well. The ISP guy convinced me that my WiFi router was faulty and that I just need to replace it or use a LAN cable for everything.

I was just about to order a new router but I wanted to do a simple test to check if my ISP was throttling Netflix and providing normal or prioritized access to Speedtest and YouTube first.

Step 1: Download and install Opera’s developer browser from this URL. This version of Opera has a VPN (Virtual Private Network) built into the browser. To enable it, open the browser -> click on the ‘menu’ button in the upper left corner of the browser -> click on settings -> privacy & security ->toggle the tick mark on the box that says ‘Enable VPN’.

Once the VPN is enabled, your ISP will see all internet traffic from that browser going to a single destination (the VPN’s servers) or to be coming from there. The server then channels the traffic to the different websites and apps you use through an encrypted tunnel which no one can spy on. If you don’t use a VPN, your ISP would be able to see you accessing YouTube, Netflix, Speedtest, etc. and change the speed to each (though they aren’t supposed to). If you are using a VPN, the ISP cannot see which website you access through the VPN. If you’re with me so far, on to step 2.

Step 2: Open up Chrome, Firefox or any other browser. Open www.speedtest.net and run a speed test. You’ll probably see the speed promised by your ISP in your plan. Open up another tab and go to www.fast.com , which is a speed testing service built by Netflix. The speed shown on fast.com is the actual speed your device is getting while accessing Netflix’s servers, so this is the speed at which a Netflix video would stream for you. Check the difference between the speed shown by Speedtest and Fast. In my case, the difference was drastic: 22.3 Mbps on Speedtest and 1.9 Mbps on Fast with the VPN enabled.

Now there’s two possible reasons for this- either the ISP prioritized Speedtest (since they know you’ll check that) and throttled Netflix or Netflix’s servers really suck, which is unlikely considering that their business depends on maximizing streaming speed. To check which one of these reasons is probable, move on to the next step.

Step 3: Open up that Opera browser you installed and make sure the VPN symbol to the left of the URL bar is blue (circled in red in screenshot) which means it is connected. Go to www.fast.com again and check the speed. I got a speed of 10 Mbps, compared to the 1.9 Mbps I got without VPN on Chrome.

VPNs usually slow down your internet speed a bit, so this result is rather surprising. It indicates that Netflix is probably being throttled and I should change my ISP as soon as possible. Next time you see that buffering symbol in the middle of a movie, don’t think about upgrading your plan or your router. Run this test, complain, and above all, use a VPN whenever possible.

Happy streaming.

Note: Please comment with the results from your ISP or if you see any flaw in this test.

Edit: /u/le_f from Reddit has pointed out that this result may indicate bad peering/routing as well and that you cannot conclude it is throttling without proof of intent. I had already complained to my ISP before this so I am still inclined to believe this is throttling, but I have made some edits in the post nevertheless. Please share if you have any such inputs.