Free online NBIB to BIBTEX converter

LaTeX editors, Overleaf projects, and some journal submission workflows require a BibTeX database instead of PubMed’s downloaded .nbib file. Converting the records creates an editable .bib file for citations while retaining the available publication metadata.

What the NBIB format is

NBIB is PubMed’s tagged citation format, based on the MEDLINE record structure. PubMed creates it through Save → Citation manager; files commonly use the .nbib extension and contain tags for PMID, authors, title, journal, publication date, volume, issue, pages, DOI, and other record data.

Reference managers use NBIB primarily for importing PubMed results. It is plain text, but its field tags and record structure are not directly usable as a BibTeX database.

What the BibTeX format is

BibTeX stores references as entries such as @article{key, ...} in a plain-text .bib file. LaTeX, Overleaf, JabRef, and many reference managers use these entries to generate citations and bibliographies.

Common entry types include @article, @book, and @inproceedings. Each entry has a citation key used by commands such as \cite{key}. A BibTeX file is portable and editable, but the converted result depends on the metadata present in the NBIB records.

Convert with Zotero

1. Install Zotero from the official Zotero website and open it.
2. Choose File → Import, select the option to import a file, and open the .nbib file. If Zotero asks for a format, select the PubMed or MEDLINE importer.
3. Review the imported items, including author names, titles, dates, page ranges, journal titles, and DOI values.
4. Select the items or collection, then choose File → Export Library or right-click the selection and choose Export Items.
5. Select BibTeX, set a filename ending in .bib, and save the export.

Zotero is suitable for occasional conversions because it lets you correct records before export. The Better BibTeX for Zotero extension adds configurable citation-key generation and is useful for libraries that will be exported repeatedly; it is a third-party extension, not part of Zotero’s core installation.

Convert with Bibutils

Bibutils is appropriate for repeatable command-line or batch processing. Its med2xml utility reads MEDLINE-style tagged records, and xml2bib converts the intermediate MODS XML to BibTeX.

Run:

med2xml input.nbib > intermediate.xml
xml2bib intermediate.xml > output.bib

These commands work in macOS and Linux shells and in Windows PowerShell when Bibutils is installed and its executables are on the system path. Otherwise, provide the full executable paths. Open output.bib in JabRef, Zotero, or a text editor and check the records before citing them.

Use an online service

Paperpile’s online PMID-to-BibTeX converter is useful when the records are identified by PubMed IDs rather than when a local NBIB file must be batch-converted. Copy the PMIDs from the NBIB records into the converter, generate the BibTeX entries, and save the result as .bib. Verify the returned metadata because the service retrieves current records and may produce different fields from the original NBIB download.

Online services should be limited to non-confidential references. Their upload, retention, and field-mapping policies vary; use Zotero or Bibutils for unpublished, restricted, or privacy-sensitive records.

Check the converted database

• Missing data: NBIB records may omit abstracts, complete page ranges, issue information, ORCID identifiers, or DOI values. Conversion cannot reconstruct fields that were absent from the source.
• Author names: PubMed commonly supplies initials rather than full given names. Check suffixes, particles, and organizational authors, which can be interpreted incorrectly by importers.
• Citation keys: Look for duplicate keys, especially among papers with the same first author and publication year. Regenerate or edit keys before compiling the document.
• Capitalization: Protect capitalization-sensitive names, acronyms, gene symbols, and chemical formulas with braces, for example title = {Effects of {DNA} repair}.
• Special characters: Compile a test document after export. Accented characters, ampersands, percent signs, underscores, and other LaTeX-sensitive characters may need escaping or an appropriate UTF-8 configuration.
• Entry types: PubMed publication types do not always map perfectly to BibTeX types. Inspect reviews, editorials, letters, guidelines, and conference material instead of assuming every record should be @article.