File l3backend-pdfmode.def not found when loading expl3
For Windows:
- Open the MikTeX Console
- Check for Update
- Updates > Update Now
- Search l3backend package
- Install the package
Since the July 1st, 2019 release of the LaTeX3 kernel, the driver-specific code contained in the l3backend
module was moved to a dedicated package in CTAN, and now l3backend
is a dependency of l3kernel
.
The description of l3backend
on CTAN says:
The functions here are defined differently depending on the engine in use. As such, these are distributed separately from
l3kernel
to allow this code to be updated on an independent schedule.
So if you updated l3kernel
only without installing l3backend
as well you'll get an error like this:
($TEXMFROOT/texmf-dist/tex/latex/l3kernel/expl3-code.tex)
! LaTeX Error: File `l3backend-<driver-name>.def' not found.
Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: def)
Enter file name:
and the solution is to install the missing l3backend
package.