Networking Tips and Tricks

Why is my wifi so slow? 10 reasons and how to fix it.

Poor wireless network performance is the most annoyed thing that you must agree with me. Technically, many factors can affect your Wi-Fi network, including the limitation of technology and the nature of physics. Most of them can be solved easily and your Wi-Fi performance will be improved. This post will try to answer the question of “Why is my WiFi so slow?” for you.

why is my WiFi so slow?The following reasons can affect the Wi-Fi performance negatively:

  • intermittent Internet connectivity (from ISP)
  • Wireless Interference
  • Obstacles (Construction materials and objects within the house)
  • Wireless Router Positioning
  • Network Congestion
  • Wireless Router Congestion
  • Long Range
  • Wireless Operating Mode
  • Wireless Router Failure
  • User device broken (Smartphone/Laptop/PC)

    1. Intermittent Internet connectivity

To answer the question “Why is my Wifi so slow?”, you must check your modem at first. This is to make sure that your Internet connection is good before going on with other possible reasons.

Sometimes, your problem comes from ISP side: broken cable, backbone network failed…

Cable modems (and optical modems) often have a diagnostics web page that can give you the details of cable signal (signal strength, upstream/downstream power levels, SNR, etc.). This information can be very useful in troubleshooting common connection issues.

If you detect that your downstream power level is too low or too high, then the problem must come from the ISP side. In that case you can call the support from ISP. The normal signal level is between -15dB and +15dB, ideally is between +8dB and -8dB.

The normal upstream power level is from 37dB to 55 dB, out of this range is a sign to indicate that your modem has something wrong.

The Signal/Noise Ratio (SNR) mesures how clear signal is, it is best over 30dB. A number lower than 30dB indicates that something wrong happens on the hop from your modem to the ISP.



  • Make some PINGs to the internet to know if your connection is intermittent.
  • Double check your cable, connectors and splitters. Remember that cable should never be bent into a too small radius.

2. Wireless Interference

Do you know that there are many wireless signals all around you? And do you know that one signal can affect others if they have the same frequency? That’s one reason explain why your WiFi is slow. Read this article for the right answer

When signals operate at the same frequency they would cancel each other. That’s one important reason explains why your Wi-Fi is so slow if interference happends.

Because Wi-Fi band (both 2.4GHz and 5GHz) is public, anyone/any device can use that band including wireless routers, microwave ovens, wireless speakers, directe satelite service… the chances that cause interference increase and happend every day.

The best way to avoid interference is making sure your wireless router using a least interference channel. Follow the steps below to eliminate interference:

  • Scan your area to find the best channel: I often use an application for Android call Wi-Fi Analyzer. Just install that app on an Android smartphone (it is best to support both 2.4GHz and 5GHz), launch it and it will scan and show which channel is free for you.
  • Go to your router configuration page and switch your router to the free channel selected from the above step.

Do these steps for both 2.4GHz and 5 GHz band, interference will be reduce to the minimum and your Wi-Fi performance can be improved.

3. Why is my WiFi so slow? It because of obstacles

Cat with slow WiFi

Wi-Fi signal propagation requires line of sight (LOS) and can be absorbed by materials. Obstacles are the most important factor that affect your Wi-Fi perfomance.

Concrets, metal, green trees, water… absorb the Wi-Fi signal much more than others. A 10cm concret wall can reduce your signal upto 10dB, you can learn how to mesure signal loss here

Once obstacles absorb/reduce most of your Wi-Fi signal, your usage can be a nightmare due to poor signal strength.

For a better Wi-Fi network, try to make sure your router isn’t blocked by any other objects.

4. Wireless Router Positioning

Most of the time, we often forget to pick a good position for the wireless router. We let them stay in a corner on the first floor of the house and cannot connect to it on the second floor. Why that?

As mentioned above, Wi-Fi signal can be absorbed by objects, if your router’s position is not optimal (in the basement for example) the signal strength will be very weak and hence your Wi-Fi is slow.

The solution is:

  • Place the router in the center of your area
  • Avoid surrounding the router with objects, especially concret/metal objects
  • The router should be install at least 1m away from other objects.
  • Keep the router stay away from microwave, when microwave works your connection could be dropped.
  • Higher is better. When your router is set up high, there are less obstacles.

5. Network congestion

This problem reduce the quality of service when one or more equipments (modem, router, switch…) is carrying more data than it can handle.

It happens when:

  • There are too many devices/users in your network. This will raise traffic demand. If your Internet contract has bandwidth lower than the total traffic demand then congestion will occur.
  • Broadcast Storm: It is a situation where there are unexpected too many requests on your network or from your device. One important thing is virus can make broadcast storm.
  • Bad configuration: for example, other network device has the same IP as your gateway; There is a loop path between two switches.
  • Outdated hardwares: These hardwares can be your bottlenecks.
  • Multicast packets can flood your network.

How to avoid network congestion:

  • Keep your network simple
  • Sign a high speed internet contract that fits your demand
  • Using Antivirus program on computer.
  • Keep your wireless network private so that less people can connect.
  • Move multicast service to a separated network

Read more about how to avoid network congestion here

6. Wireless Router congestion

It is the same as network congestion but wireless router has some more specifics. It is the most common reason that you may have today.

When wireless router congestion occurs, every people connected to that router will have a very slow connection and new people even cant not connect to it.

The followings are main reasons:

  • Too many devices associated to the router: Each router has a limit number of associated clients that it can handles, over that number will make the router unresponsible or hang.
  • High traffic from clients. Each router just can handle a limit number of bandwidth (in theory:  802.11b is 11Mbps, 802.11g is 54Mbps, 802.11n is 450Mbps, 802.11ac is 1300Mbps).

7. Distance

The distance beetwen router and your device affects significantly to your connection perfomance.

Your speed will be fast if you stay close to the router, but your wifi will be very slow when you move away from the router. That is because the loss of signal.

Longer distance means more loss and more transmission failures. Each data packet failure will require a re-transmission. With a limited bandwidth, more re-transmission means less bandwith for your connection.

Each wireless router has a parameter called receiver sensitivity (RX sensitivity). The router just can understand the signal if it is bigger than the RX sensitivity. Below that value will make loss packet.

Consumer routers and Wi-Fi endpoints (smartphone, laptop…) often have RX sensitivity of around -90dB. The normal acceptable value fo a good connection is above -75dB, so be sure to stay close to your router enough.

8. Wireless Operating Mode

Do you know that Wi-Fi has several standards? They are 802.11b, 802.11g, 802.11n, 802.11ac and will be more in the furute.

Wi-Fi standards
Wi-Fi standards

802.11b is the eldest and slowest standard, it provides only 11Mbps in total bandwidth. The newest standard is 802.11ac, it can prodive upto 1.3Gbps.

If your WiFI connection is slow, maybe your router is configured in a old standard. So please try to config your router with a newer standard.

9. Wireless Router Failure

This reason is clear, failure will affect connection for sure. For example, after a hard crash the internal antenna inside your router could be detached, then the signal strength will drop and make your connection slow.

If you found your router is broken, the most simple way to fix is purchasing a new router. And in this case, I wrote some best wireless router buying guide for you.

10. User device broken (Smartphone/Laptop/PC)

The same as broken wireless router, any failure happens inside your device will cause slow WiFi as well.

The most common problems found in user’s device are:

  • Broken WiFi adapter.
  • Outdated WiFi adapter
  • Broken Wireless driver
  • Short circuit

Final words.

A deep understanding of the above reasons will help you identify your problems easily. Now with these basic knowledges, I hope you can answer the question why your WiFi is so slow. The most common reason is:

  • Broken device
  • Interference by your neighbors or other routers.
  • Obstackles (concret walls, electric device, trees…)

In case you can’t improve your wireless connection, you can contact me then I can help you. Just comment bellow or drop me an email about your problems.

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