Undefined References (BibTeX/Biber Not Run)
LaTeX Warning: There were undefined references.
What this error means
The document has bibliography references that were never resolved. This usually means the BibTeX or Biber processor was not run as part of the compilation sequence, so the reference data was never collected.
Common causes
- Compiling only once with pdflatex instead of running pdflatex → bibtex → pdflatex → pdflatex
- Running bibtex on the wrong .aux file
- Using biblatex/biber but only running pdflatex, not biber
- Stale .aux files from a previous run
How to fix it
For traditional BibTeX: run pdflatex → bibtex main → pdflatex → pdflatex. For biblatex with Biber: run pdflatex → biber main → pdflatex → pdflatex. Delete .aux files if you get persistent undefined reference warnings after the full sequence.
Code examples
% Only ran: pdflatex main.tex
% Missing: bibtex main -> pdflatex -> pdflatex% Full BibTeX sequence:
% 1. pdflatex main.tex
% 2. bibtex main
% 3. pdflatex main.tex
% 4. pdflatex main.tex
% Full biblatex+biber sequence:
% 1. pdflatex main.tex
% 2. biber main
% 3. pdflatex main.tex
% 4. pdflatex main.texRelated errors
File Not Found
! LaTeX Error: File 'XXX' not found.
Unknown Graphics Extension
! LaTeX Error: Unknown graphics extension: .XXX.
Unicode Character Not Supported (pdfLaTeX)
! Package inputenc Error: Unicode char U+XXXX not set up for use with LaTeX.
Cannot Determine Size of Graphic (No BoundingBox)
! LaTeX Error: Cannot determine size of graphic (no BoundingBox).
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