You wanted customized…

You got customized. If you go into the Advanced tab of the Better BibTeX preferences you will find a text box (empty by default) where you can edit a javascript snippet which will be executed for each reference generated in the Bib(La)TeX exporter. In this code, you have access to the reference just before it will be written out and cached. There is an API to do this, and it’s fairly stable, but usually you can just open a new issue and ask me to write it, and I’ll add it here (it’s how the examples got here). Postscripts are available in 4 of the translators:

  1. BetterBibLaTeX
  2. BetterBibTeX
  3. BetterCSLJSON
  4. BetterCSLYAML

You can (and totally should) check in which translator your postscript is running, which you can do by testing for Translator.<id> where <id> is one of these four names, using something like

if (Translator.BetterBibLaTeX) {

or alternately on the full name using a switch

switch (Translator.header.label) {
  case 'Better BibLaTeX':
  case 'Better BibTeX':
  case 'Better CSL JSON':
  case 'Better CSL YAML':

If you want to run a postscript in the CSL translators but don’t care whether it will output YAML or JSON, you can test for Translator.BetterCSL, which will be true when either one of BetterCSLJSON or BetterCSLYAML is active. Analogously, Translator.BetterTeX will be true if either of Better BibTeX or Better BibLaTeX is active.

In the postscript, the reference being built is available as reference, and the Zotero item it is being built from is available as item. For backwards compatibility, in the BetterBib(La)TeX contexts, the reference being built is also available as this, and the Zotero item it is being built from as this.item, but use of these is discouraged now.

You should really test for the translator context in your postscripts using the Translator.<name> tests mentioned above. If you don’t because you have a postscript that pre-date postscript CSL support, you will probably be using the legacy use of this to set things on the reference being built, and calling reference.add in those postscripts; since, for CSL postscripts, this is not set, it will make the script will non-fatally error out, so you’re very probably good to go as-is. But please fix your postscripts to test for the translator context.

The API for Better BibTeX and Better BibLaTeX

The postscript should be a javascript snippet. You can access the data with following objects and methods:

  • item is the Zotero item that’s the source of the reference.

  • reference is the BibTeX reference you are building, and the reference has a number of fields.

    e.g. you can access the date in zotero item

  • reference.has is a dictionary of fields for output.

  • is the parsed and normalized version of

    e.g. you can see whether the year field has been set by testing for reference.has.year, and when e.g. for a season-date only the year is exported in bibtex, you can find it in

  • reference.add is the function to add or modify keys in reference.has. It accepts the following named parameters in the form of an object:

    • name: name of the bib(la)tex field to output
    • value: the value for the field without LaTeX encoding
    • bibtex: the value for the field with LaTeX encoding already applied. If both bibtex and value are present, bibtex takes precedence
    • enc: specifies how to encode the value field. Valid values are:
      • latex: encode markup and special characters to LaTeX. This is the default, if you don’t provide an enc parameter, latex is assumed
      • verbatim: encode under verbatim rules
      • literal: encode under literal rules
      • raw: assume value is already LaTeX-encoded (same as passing the value in bibtex)
      • url: encode as verbatim url
    • sep: if value is an array, and enc is latex, encode each array element using latex and join the results with the string in sep. Defaults to an empty string.
    • html: boolean indicating whether the value is full HTML (really only useful for notes)

    e.g. change the value of year in output reference.add({name: 'year', value: "your_year_value"})

  • reference.addCreators adds the contents of item.creators to reference.

    author encoding has a fair number of moving bits and generates multiple fields (author, editor, etc), this function is here so you can manipulate item.creators and call reference.addCreators to replace the existing creator fields on reference.

  • reference.remove removes a field previously added by reference.add or reference.addCreators

The API for BetterCSLJSON and BetterCSLYAML

  • reference is the CSL object being built. Any changes made to this object will directly change the CSL object being output.
  • item is the Zotero reference it’s being built from.

There isn’t really an API. You can use regular javascript to manipulate the reference object, which is a CSL-JSON object.


There isn’t much in place in terms of debugging, as tranlators (and thus postscripts) are not allowed to do any UI work. You can do old-fashioned printf-style debugging by calling Zotero.debug(...) in your postscript – it will output the string you pass into the Zotero debug log which you can inspect from the Help menu. You can for example do Zotero.debug(JSON.stringify(item)) to see what the Zotero item looks like to the translator.


Add accessdate, url for BibTeX

Since BibTeX doesn’t really have well-defined behavior across styles the way BibLaTeX does, BBT can’t generate URL data which is compatible with all BibTeX styles. If you know the style you use yourself, you can add the data in the format you want using a postscript. The script below will add a note for the last accessed date, and a \url tag within the howpublished field, but only for BibTeX, not for BibLaTeX, and only for webpage entries:

if (Translator.BetterBibTeX && item.itemType === 'webpage') {
    if (item.accessDate) {
      reference.add({ name: 'note', value: "(accessed " + item.accessDate.replace(/\s*T?\d+:\d+:\d+.*/, '') + ")" });
    if (item.url) {
      reference.add({ name: 'howpublished', bibtex: "{\\url{" + reference.enc_verbatim({value: item.url}) + "}}" });

Comma’s in keywords

If you want to retain commas in your keywords (e.g. for chemical elements) and separate with a comma-space, you could do:

if (Translator.BetterTeX) {
  reference.add({ name: 'keywords', value: item.tags, sep: ', ', enc: 'tags' });

as the default encoder knows what to do with arrays, if you give it a separator.

Add DOI in note field

if (Translator.BetterTeX && item.DOI) {
  var doi = item.DOI;
  if (doi.indexOf('doi:') != 0) { doi = 'doi:' + doi; }
  reference.add({ name: 'note', value: '[' + doi + ']' });

Add arXiv data

arXiv is a bit of an odd duck. It really isn’t a journal, so it shouldn’t be the journal title, and their own recommendations on how to include arXiv IDs is a little lacking: this doesn’t say where to include the arXiv:... identfier, and this says not to include it. Nor does it give any recommendations on how to achieve the desired output.

But for arguments' sake, let’s say you get the desired output by including an empty journaltitle field (ugh) and stuff the arXiv:... ID in the pages field (ugh). You could do that with the following postscript:

if (Translator.BetterTeX && {
  reference.add({ name: 'pages', value: });
  if (!reference.has.journaltitle) { reference.add({ name: 'journaltitle', bibtex: '{}' }); }

Custom field order

Specify the ordering of the listing of fields in an exported Biblatex/Bibtex entry. Your postscript:

if (Translator.BetterTeX) {
  // the bib(la)tex fields are ordered according to this array.
  // If a field is not in this list, it will show up after the ordered fields.

  const order = ['author', 'date', 'title', 'publisher']
  for (const [field, value] of order.filter(front => reference.has[first]).concat(Object.keys(reference.has).filter(other => !order.includes(other))).map(f => [f, reference.has[f]])) {
    delete reference.has[field]
    reference.has[field] = value

In Zotero when using an Export Format of Better Biblatex we’ll get something like the following entry …

  author = {Nietzsche, Friedrich Wilhelm},
  date = {1974-03},
  title = {The {{Gay Science}}: {{With}} a {{Prelude}} in {{Rhymes}} and an {{Appendix}} of {{Songs}}},
  publisher = {{Random House}},
  origdate = {1882},
  shorthand = {GS},
  keywords = {Philosophy / General,Philosophy / History  Surveys / Modern},
  translator = {Kaufmann, Walter},
  timestamp = {2016-06-05T20:12:28Z},
  pagetotal = {407},
  shorttitle = {The {{Gay Science}}},
  isbn = {0-394-71985-9},
  edition = {1}

Further details Export to Biblatex/Bibtex. Custom field order. #512.

Detect and protect LaTeX math formulas

if (Translator.BetterTeX && reference.has.title) {
  reference.add({ name: 'title', value: item.title.replace(/(\$.*?\$)/g, '<script>{$1}</script>') });

Or, detect and protect (simple) LaTeX commands

if (Translator.BetterTeX && reference.has.journal) {
  reference.add({ name: 'journal', value: reference.has.journal.value.replace(/(\\\w+)/g, '<script>{$1}</script>') });

Detect and protect MathJax

if (Translator.BetterTeX) {
  // different for bibtex and biblatex exporters
  const note = ['annotation', 'note'].find(field => reference.has[field])

  if (note) {
    let notes = => `<div>${note}</div>`).join('')
    notes = notes
      .replace(/(\$\$[\s\S]*?\$\$)/g, '<script>$1</script>')
      .replace(/\\\(/g, '<script>$')
      .replace(/\\\)/g, '$</script>')
    reference.add({ name: note, value: notes, html: true });

Replace director with author for videoRecording and film references

Creator handling is fairly complicated, so to change the authors/editors/creators of any kind, you must change them on item and then call addCreators to do the needful. addCreators will replace the existing creators that were added to reference with the current state in item.creators, however you left it.

if (Translator.BetterBibLaTeX) {
  switch (item.itemType) {
    case 'videoRecording':
    case 'film':
      for (const creator of item.creators) {
        if (creator.creatorType === 'director') creator.creatorType = 'author'

Changing the reference type from collection to book

if (Translator.BetterBibLaTeX) {
  if (reference.referencetype === 'collection') reference.referencetype = 'book'

Set the reference type to misc for arXiv preprints in BibTeX

if (Translator.BetterBibTeX && reference.referencetype === 'article' && item.arXiv) {
  if (reference.has.journal && item.arXiv.source === 'publicationTitle') {
  if (!reference.has.journal) reference.referencetype = 'misc'

Citing documents with a physical archive location

This is one area where some of the supposedly most popular packages – biblatex, biblatex-apa, biblatex-chicago, biblatex-mla – are all over the place, if they explicitly support archival material at all. There doesn’t seem to be a solution that caters for all of these and possibly other packages, too. biblatex has no special fields for dealing with info about physical archives, even if it does have provisions for electronic archives via the fields eprint (identifier), eprintclass (section of an archive), and eprinttype (name of the archive).

Of the packages mentioned above, only one (biblatex-mla) has a clear schema of how to record archival information (type @unpublished; fields number, library, location). Note that the library field is unique to biblatex-mla. (biblatex does define the field, but never uses it in its standard styles, and we find no indication that either biblatex-apa or biblatex-chicago would use it for a physical archive.)

Given all of this, I’m going to leave referencing of physical location to postscripts for now. If you enable the quality report, BBT will list Zotero fields with data that has not been used in the export:

  title = {Un Million et Demi d'infirmes, Handicapés Physiques et Mentaux},
  date = {1968-05-31},
  url = {},
  urldate = {2021-04-08},
  type = {Letter}
% == BibLateX quality report for MillionDemiInfirmes1968:
% Unexpected field 'title'
% Unexpected field 'type'
% ? Unused archive: Archives de la Ville et l'Eurométropole de Strasbourg
% ? Unused archiveLocation: 114 Z 1 248
% ? Unused callNumber: 114 Z 1 248

if you then apply a postscript such as

if (Translator.BetterBibLaTeX) {
  // biblatex-mla
  if (item.archive && item.archiveLocation) {
    reference.add({ name: 'type', value: reference.referencetype })
    reference.referencetype = 'unpublished'
    reference.add({ name: 'library', value: item.archive})
    reference.add({ name: 'number', value: item.archiveLocation })

you get

  title = {Un Million et Demi d'infirmes, Handicapés Physiques et Mentaux},
  date = {1968-05-31},
  url = {},
  urldate = {2021-04-08},
  type = {letter},
  library = {Archives de la Ville et l'Eurométropole de Strasbourg},
  number = {114 Z 1 248}
% == BibLateX quality report for MillionDemiInfirmes1968:
% Unexpected field 'number'
% Missing required field 'author'

Export season for BibTeX

if (Translator.BetterBibTeX && === 'season') {
  reference.add({ name: 'month', value: ['', 'spring', 'summer', 'fall', 'winter'][] })

Adding rights field in BibLaTeX

if (Translator.BetterBibLaTeX) {
  reference.add({ name: 'rights', value: item.rights});