I am using biblatex. If I cite
\cite{author1,author2}
I obtain
[1], [2].
How could I cite such that references now live under the same bracket,
[1,2]?
As discussed in the comments, you were using style=ieee, which displays all citations in separate brackets.
If you don't particularly care about IEEE style in the bibliography, you can just go for
\usepackage[backend=biber, style=numeric, sorting=none]{biblatex}
to get the usual behaviour that places all numbers in the same pair of brackets.
If you want to compress ranges as well, use numeric-comp instead of numeric. See Citing a range of papers using numeric keys as in \cite{a, b, c} -> [1-3].
If you want to retain the IEEE bibliography style, you can select numeric only as citation style
\usepackage[backend=biber, bibstyle=ieee, citestyle=numeric, sorting=none]{biblatex}
style=numeric-comp,instead ofstyle=numeric,. See https://tex.stackexchange.com/q/3871/35864. – moewe May 04 '22 at 20:06style=numeric,should be "[1,2]" already. If you get "[1], [2]" either you are not usingstyle=numeric,or something is wrong.numeric-compshould only become relevant once you cite a larger range ("[1,2,3]" vs "[1-3]"). Please show us a small example document that reproduces the output you are currently getting with as little code as possible. – moewe May 04 '22 at 20:22\usepackage[style=ieee,style=numeric]{biblatex}! However, the cites now appear not by order of appearance, but[1,124], for example. – hyriusen May 04 '22 at 20:42\usepackage[style=ieee,style=numeric,sorting=none]{biblatex}it was solved! Thank you. – hyriusen May 04 '22 at 20:54\usepackage[style=ieee,style=numeric,sorting=none]{biblatex}is equivalent to\usepackage[style=numeric,sorting=none]{biblatex}because multiplestyles overwrite each other. – moewe May 05 '22 at 05:52