Custom Bibliography formats or styles in Word
Microsoft Word has many supplied Bibliography formats or styles to choose from. You can add your own custom formats to suit your needs (or your professors).
First, a quick look at how Word figures out how to format or arrange a citation.
See: Add a Bibliography to Word documents
Citations for everyone in Word
Note: this is another case where Microsoft insists on using the word ‘style’ for something other than formatting Styles in Word. The makeup or arrangement of a citation (i.e the order of author, publication, date etc) is also called a style … to the confusion of many.
The in-built citation styles are listed at References | Citations & Bibliography | Style

That list is made by Word from the .XSL files in the folder \Microsoft\Bibliography\Style
(for Microsoft 365 Windows that’s \Users\<username>\AppData\Roaming\ Microsoft\Bibliography\Style
) which contains a collection of .xsl files.

For those of you not up on your XML-speak, an XSL file tells software how to present or transform data for presentation.
Make your own Bibliography format or style
It’s possible to make your own Bibliography/Citation format or XSL. It’s not a simple thing to do, not for the faint of heart and definitely NOT anyone with a looming deadline.
The formatting isn’t simple at all. There are different requirements for things like dated and non-dated sources or human vs corporate authors. The supplied Word XSL bibliography formats range from over 5,600 lines of code to 9,300 lines for the Turabian option.
Microsoft has a long, complex page that goes into some detail but there are many shortcuts they don’t mention (but we will).
It’s already been done
If your institution, department or professor has a different Bibliography format, they should have a Word compatible XSL you can use.
Failing that, presumably other students (current or past) have the same problem. Ask around to see what they did and hopefully someone already made an XSL you can copy.
BibWord (more on that in a moment) has a library of Word Bibliography XSL files to download.
Adapt existing format
If you must make your own Bibliography style, start with an existing XSL that’s closest to what you need and make the changes.
XSL files are plain text. Open in any text editor, preferably one with coding support like NotePad++ then carefully change the parts that don’t suit you.
Simple changes
Some changes are relatively simple once you know where to look.
A common question is changing the open and close brackets for a citation. These are controlled by the OpenBracket
and CloseBracket
names (search for those terms in a Word XSL and they’ll appear.
After the line:
<xsl:value-of select= "/*/b:Locals/b:Local[@LCID=$_LCID]/b:General/b:OpenBracket"/>
Or
<xsl:value-of select= "/*/b:Locals/b:Local[@LCID=$_LCID]/b:General/b:CloseBracket"/>
Add the text
<xsl:text>{</xsl:text>
With your choice of open or close brackets. The final result looks like this:
In the same part of the XSL you’ll find other common settings like:
OpenQuote
CloseQuote
FromToDash
OpenLink
CloseLink
AuthorsSeparator
ListSeparator
GroupSeparator
EnumSeparator
Search for those terms in the XSL.
BibWord
BibWord is an open-source tool for making or changing Word bibliography XSL files.
Start with BibWord_Guide.docx as a guide to the makeup of the XSL files.
Add a Bibliography to Word documents
Citations for everyone in Word
Citation and Bibliography tools beyond Word
Find and cite with Researcher in Word
Using the Source Manager for citations in Word
Understanding Citations and Sources in Microsoft Word