Which Style Manual to Use, and What Changes If You Pick the Other One

The destination names the manual

Journals say so directly. The International Committee of Medical Journal Editors repeatedly directs authors to consult the specific journal they intend to submit to, rather than relying on general recommendations.³ PLOS ONE names its choice: references follow Vancouver style, numbered in the order they appear in the text and cited in square brackets.⁴

Presses do the same by convention rather than by instruction, and most American trade and scholarly publishing runs on Chicago. Its eighteenth edition appeared in 2024 and expanded its coverage into fiction and other creative genres for the first time.⁵ Federal agencies run on the GPO Style Manual. Scientific publishing has its own reference in the CSE Manual, whose ninth edition carries a 2024 copyright and covers reference formatting, tables, figures, and the difference between American and British conventions.⁶

An author choosing a manual before knowing the destination is answering a question that has not been asked yet. An author who knows the destination usually finds the answer published.

What actually changes when the manual changes

The differences are real but finite, and they cluster in six places.

Numbers are the first, and the case above is the whole of it in miniature. Punctuation in a series is the second. The GPO requires a comma after each member within a series of three or more words, phrases, letters, or figures used with and, or, or nor, and gives red, white, and blue as its example.⁷ Reference format is the third, and it is the most visible, since a numbered Vancouver list and an author-date list look nothing alike on the page.⁴

Capitalization of headings is the fourth, and it is where inconsistency shows fastest in a long document. Treatment of abbreviations is the fifth. ICMJE asks for standard abbreviations only, notes that nonstandard ones confuse readers, and advises against abbreviations in the title.³ Units are the sixth, and ICMJE asks for metric units for length, height, weight, and volume, with temperatures in degrees Celsius.³

Almost nothing else changes. The manuals do not disagree about grammar, and they do not disagree about whether a sentence means what it says.

The decision costs nothing until it is made twice

A manuscript that has named its manual has converted six open questions into six answered ones, each checkable against a written source. A manuscript that has not named one answers them differently in chapter two and chapter nineteen, and no later reader can tell which answer was intended.

The record of those answers has a name and a place in the profession. Editors Canada includes the development of style sheets within copy editing, alongside checking mechanical consistency.⁸ The Editorial Freelancers Association describes copyediting in the same terms, down to preparing the style sheets that guide consistency and accuracy across a manuscript.⁹

A style sheet is worth asking for at the end of any copyediting or proofreading job, because it is the document that makes the next manuscript cheaper. It records the manual chosen and every decision the manual did not cover.

What the manual cannot settle

No manual rules on whether a sentence is clear, whether a paragraph belongs where it sits, or whether a figure is the right figure. Those are the questions an author and their reviewers answer, and a manuscript can be perfectly conformant and still hard to read.

Where a client has chosen an authority, EditFast works to it and records the decisions on a style sheet returned with the manuscript. Where a client has not chosen one, we ask where the document is going, because that usually settles it. Everything a client sends is treated in confidence, including unpublished manuscripts, submissions, and correspondence with a publisher.

Choosing a manual is often described as a matter of preference. It is closer to choosing a unit of measurement. Any of them will do, and mixing two of them will not.