Why "online DAW" describes two different products
Half of these tools are timeline recorders: a track list, a playhead, audio and MIDI regions you arrange, plus a modest set of built-in instruments. The other half are instrument collections with sequencing attached - the emphasis is on making the sound rather than on laying out a song. Both are legitimately called an online DAW and they suit different people completely. If you mostly record guitar and vocals and arrange them, you want the first kind. If you mostly design sounds and build beats, you want the second, and GOONS is firmly in that camp.
Free is a real answer
BandLab is free and it is good. For a teenager with no budget and no equipment, "free, runs on your phone, and your friends are already there" beats any argument about oscillator quality. The honest case for paying is depth and independence - 20+ separate instruments rather than one general-purpose editor, and a platform whose business model is your subscription rather than your attention. That trade is not right for everyone and the free music software page argues both sides of it.
The two searches that have no honest product answer
A large share of the traffic in this category is people typing "GarageBand for Windows" and "FL Studio online". Neither product exists in that form, and the results are mostly download sites you should not visit. Those two pages - GarageBand for Windows and FL Studio online - say so plainly and then describe what the person was actually looking for.