Comment by diggan

Used to use Tree Style Tab too! But I think Sideberry is better in terms of feeling snappier, at least that's what I remember from moving from TST to Sideberry.

Right now, I have ~110 tabs open, and the "Extensions" item in about:processes shows ~400MB used, but that's all extensions, ~10 in total, not just Sideberry. But to be honest, I'm not sure I'd notice performance issues until too late, as I'm sitting on quite a bit of RAM already.