Why Use a .sty File?

Creating Your First .sty File

A style file is a plain text file with a .sty extension. At minimum, it needs one line to identify itself. Create a file called mycommands.sty in the same directory as your .tex file:

Then load it in your document:

Anatomy of a .sty File

• \NeedsTeXFormat{LaTeX2e} — Declares that this package requires LaTeX2e (the current standard). Optional but good practice.
• \ProvidesPackage{name}[date description] — Identifies the package. The name must match the filename (without .sty). LaTeX uses this to prevent loading the same package twice.
• \RequirePackage{name} — The .sty equivalent of \usepackage. Use this instead of \usepackage inside style files to load dependencies.
• \newcommand, \renewcommand, \newenvironment — Your custom definitions.
• \endinput — Marks the end of the file. LaTeX stops reading here. Optional but recommended.

Common Patterns

Custom Environments

Style files can define custom environments, not just commands:

Package Options

You can make your style file accept options:

Load with options: \usepackage[draft]{mycommands}

Operator Shortcuts

A popular pattern is bundling field-specific operator macros:

Using .sty Files in Online Editors

Online editors fully support custom .sty files. Upload the file to your project root (or a subdirectory), and use \usepackage as normal:

• Click "Upload" in your editor's file panel and select your .sty file
• Add \usepackage{mycommands} to your preamble
• If the file is in a subdirectory, use \usepackage{subdir/mycommands}

The .sty file is included when you download the project as a .zip or submit to a journal, so your co-authors and reviewers will have it automatically.

.sty vs .cls Files

You may also encounter .cls files. The distinction is simple:

• .sty (style file) — Loaded with \usepackage. Adds commands and features. You can load multiple .sty files.
• .cls (class file) — Loaded with \documentclass. Defines the document type (article, book, etc.). You can only have one.

Conference templates (like NeurIPS or ICML) typically provide a .cls file for the document layout and sometimes a .sty file for additional macros. Your own custom notation should go in a .sty file.

Best Practices

• Use \newcommand not \def — \newcommand gives an error if the command already exists, preventing silent overwrites. \def silently replaces existing commands.
• Prefix internal commands with @ — Commands like \my@internal@helper won't clash with user-level commands. The @ character is not normally allowed in command names in .tex files, so this provides a natural namespace.
• Use \RequirePackage instead of \usepackage — They do the same thing, but \RequirePackage is the convention inside .sty files and works before \documentclass.
• Keep one file per concern — If your macros grow large, split into math-notation.sty and formatting.sty rather than one giant file.
• Version your .sty files — Include a date in the \ProvidesPackage line. Track changes in Git alongside your documents.

Starter Template

Copy this template and customize it for your field: