When your bibliography won't build, the problem is almost always one of a handful of recurring mistakes. Paste your .bib into our free BibTeX validator to spot them instantly, or work through the list below.
1. Missing required fields
Each entry type requires certain fields. An @article needs author, title, journal, and year; an @inproceedings needs booktitle instead of journal. A missing required field produces a "missing field" warning and a malformed reference. Add the field or switch to the correct entry type.
2. Unbalanced braces
Every { needs a matching }. A single missing brace often breaks every entry after it, which is why one typo can produce dozens of errors. Check the entry just before the first reported error.
3. Duplicate citation keys
Two entries with the same key (e.g. @article{smith2020, ...} twice) cause BibTeX to use only one and warn about the collision. Make every key unique.
4. Unescaped special characters
Characters like &, %, #, and _ are special in LaTeX. In a title or journal name, escape them (\&, \%) or they will break the build.
5. Missing commas between fields
Fields are separated by commas. Forgetting one - especially after a closing brace - produces a confusing parse error. Make sure every field line except the last ends in a comma.
6. Smart quotes and stray Unicode
Pasting from a website or PDF can introduce curly quotes or non-ASCII characters that BibTeX chokes on. Replace them with plain ASCII, or use a UTF-8-aware engine like Biber.
Running your file through the validator catches all six categories before you waste a compile cycle.