Hi whatiskwt, glad to see you in Mozilla Support Forum.

The reason of your problem could be extensions or add-ons.

You can check this by opening firefox in safe mode.

• Find the Firefox icon or click Start and type Firefox.
• Hold down the Shift key on the keyboard and then click the Firefox icon.
• In the Firefox Safe Mode window, click the Start in Safe Mode option.

If it gives you good result in safe mode, then you can reset your firefox in default mode by following steps:-

• Click the menu icon, then click on “Help”. Click on Firefox's main menu button, represented by three horizontal lines.
• Click “Troubleshooting Information”. From the Help menu, click on “Troubleshooting Information“.
• Click on “Refresh Firefox”.
• Confirm.
• Click “Finish”.

If it doesn't solved your problem, then feel free to ask in Reply Section. Thanks for raising your question in Mozilla Support Forum.

Hello whatiswt, It is completely normal that Firefox is a bit slower than the other browsers because it takes up more resources comparing to it's rivals. That is because Firefox has more privacy protections and Add-Ons that eat up more CPU.

To make Firefox faster, I really just recommend to remove some more useless extensions since a lot run in the background all the time.

I really hoped you learned something from this and, I'd love if you tell me if you see a difference., Stay Safe!

Hi whatiskwt, glad to see you in Mozilla Support Forum. The reason of your problem could be extensions or add-ons. You can check this by opening firefox in safe mode.

• Find the Firefox icon or click Start and type Firefox.
• Hold down the Shift key on the keyboard and then click the Firefox icon.
• In the Firefox Safe Mode window, click the Start in Safe Mode option.

If it gives you good result in safe mode, then you can reset your firefox in default mode by following steps:-

• Click the menu icon, then click on “Help”. Click on Firefox's main menu button, represented by three horizontal lines.
• Click “Troubleshooting Information”. From the Help menu, click on “Troubleshooting Information“.
• Click on “Refresh Firefox”.
• Confirm.
• Click “Finish”.

If it doesn't solved your problem, then feel free to ask in Reply Section. Thanks for raising your question in Mozilla Support Forum.

Hi, I already did that, it didn't change anything. :(

Hello whatiswt, It is completely normal that Firefox is a bit slower than the other browsers because it takes up more resources comparing to it's rivals. That is because Firefox has more privacy protections and Add-Ons that eat up more CPU. To make Firefox faster, I really just recommend to remove some more useless extensions since a lot run in the background all the time. I really hoped you learned something from this and, I'd love if you tell me if you see a difference., Stay Safe!

I will test that once i'll find back my laptop and the higher connection...

Alright!

To make Firefox faster, I really just recommend to remove some more useless extensions since a lot run in the background all the time. I really hoped you learned something from this and, I'd love if you tell me if you see a difference., Stay Safe!

Hi! There a small difference between with Disconnect add-on active and inactive. It's a bit faster when it's inactive for the download speed.

But my question was about the UPload speed, which is stuck to 135 Mbits/s in firefox and 200 Mbits/s in Edge. I have bought an ethernet wire which is cat. 7 s/ftp but not received yet (the french mail group is not very fast due to covid-19...) will I see a difference? thanks.

Firefox is slow :( But, maybe you can improve it a little.

• Try to empty the (totally useless) "features folder" ( C:\Program Files\Mozilla Firefox\browser\features\ ) and disable/remove the plugins/extensions that you don't use.
• I use to delete the files inside "features" and disable/uninstall firefox's extensions that i don't use, after every firefox update. (because firefox stupidly recover and enable all again at every update! Even Bing extension!)
• I suggest to keep a copy of every file inside "features" folder to another folder, so you will bring them all back to previous state if you need. (backup)

Sometimes Windows reserves some resources and prevent software other than MS software from using the full internet bandwidth and this means that Firefox is slower.

• https://en.wikipedia.org/wiki/Quality_of_service

Your security software also can prevent Firefox from reaching full speed by monitoring the connection.

You can boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• https://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

Your security software also can prevent Firefox from reaching full speed by monitoring the connection.

Yes I am aware of this, and I already disabled a lot of parameters in kaspersky about internet protection. That improved the download speed but not the upload speed. If I have a big file to upload, i will use Edge, et puis voilà (in french :).