# LaTeX Citation Error Checker

Paste your .tex and .bib content below. Instantly find undefined citations, missing bibliography entries, and mismatched cite keys.

### LaTeX source.tex

### Bibliography.bib

Check citations →

## Citation analysis

@Paste your .tex and .bib content, then click check

## Common LaTeX citation errors

### Undefined citation \[?\]

LaTeX shows \[?\] when a \\cite{} key doesn't match any entry in your .bib file. Usually a typo or missing entry.

**Fix:** match key exactly, case-sensitive

### Citation on input line X

LaTeX log warning. Means you ran BibTeX before the .aux file was updated. Run compile twice.

**Fix:** pdflatex → bibtex → pdflatex → pdflatex

### Empty bibliography

The \\bibliography{} command points to a .bib file that is empty, missing, or misnamed.

**Fix:** check \\bibliography{filename} matches filename.bib

### \\cite vs \\citep vs \\citet

Using \\cite{} with natbib can produce unexpected output. \\citep gives (Author, year), \\citet gives Author (year).

**Fix:** use \\citep / \\citet with natbib packages

### Duplicate bib keys

Two entries with the same key — BibTeX uses the last one silently. Can cause wrong citations.

**Fix:** each @entry needs a unique key

### Multiple citations \[?,?\]

\cite{a,b,c} requires all three keys to be defined. One missing key makes all show as \[?\] in some engines.

**Fix:** verify each key in \cite{a,b,c} individually

### Check citations live as you write

Bibby AI highlights undefined citations in real-time — no more compile-check-fix loops.

## Frequently asked questions

- Why does LaTeX show \[?\] instead of my citation number?
- What's the difference between \\cite, \\citep, and \\citet?
- How do I fix "I found no \\citation commands" in BibTeX?
- Can I check citations without compiling?