Trying to record sound from computer as mp3 with audacity

This is probably simple but I have been messing with it a few days, I will try to be brief

Windows 7 professional, Dell tower pc, using audacity 2.1.0 trying to record sound I hear thru the pc (via firefox browswer) into an mp3.

My setup is a bit unique I use a line6 usb audio interface for my guitar, so in audacity under edit/preferences I have devices set as wubdiws directsound (ive tried all three MME and WASAPI btw no luck), playback speakers line6 ux2, recording digital audio interface line6 ux2, channels 2 stereo.

I go in and play something thru firefox (audio off a video), I open audacity, i click “monitor” or “record” i see nothing “coming in” just a flat line and no sound.

I went into the pc side of things for playback devices and confirmed line6 ux2 is chosen, went into recording preferences, clicked listen to this device set as line6 ux2, made sure level was up not muted or 0, have messed around with a few different settings on both the audacity and on the pc side of things to try and get this to work, but whenever I play (and can hear) the audio from a video off firefox, in audacity doesn’t matter what I choose it’s not “hearing it” I get flatline nothing when i try to record.

I spent about half hour each night trying different settings here with no luck so I figured I would ask it’s probably something SO simple idk hopefully I have helped give some info here to maybe start to try and sort out what I am doing wrong?

Originally what I was trying to do was record my guitar track ALONG side the live sound of a backing track off firefox (youtube video), I can record the guitar fine but even just trying to record ONLY the audio from the firefox/youtube video i can’t get audacity to “hear” it to record it separately much less real time with me playing along with it.

Firefox cannot choose its playback device. If you want to use Line 6 as the default computer playback device, then the settings in Audacity’s Device Toolbar to record Firefox have to be Windows WASAPI host, Recording Device: Line6 ux2 (loopback), Recording Channels: 2 stereo, Playback Device: Line6 ux2.

Turn off Transport > Software Playthrough in Audacity. If you hear echoes, turn off “Listen to this device” for the Line6 recording device in Windows Sound.

Note that if you have copyright holders’ permission to record this YouTube backing track, you can simply download the video using a Firefox extension. In Firefox, look in Tools > Add-ons then search, or search online for “Firefox download video”. Install FFmpeg from Then drag the downloaded video into Audacity and Audacity will extract a copy of the audio, in as good a quality as it is in the video.

When you record your guitar over the YouTube backing, change the Audacity recording device to the Line6 ux2 input you were using before, and make sure Transport > Overdub is enabled in Audacity. If you want to hear your guitar playing live, connect headphones to the ux2. Don’t use Transport > Software Playthrough or “Listen to this device” because that has latency and you will hear yourself late.