> For the complete documentation index, see [llms.txt](https://overleaf-pro.ayaka.space/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://overleaf-pro.ayaka.space/latex/latex-errors/13-latex-error-can-be-used-only-in-preamble.md).

# LaTeX Error: Can be used only in preamble

This error appears when you have included a package or class in the main body of your document, instead of in the preamble. The preamble to the document consists of everything written before **`\begin{document}`**. In the preamble you define the type of document you are writing, the language and several other elements. For instance, a normal document preamble would look like this:

```latex
\documentclass[12pt, letterpaper]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}

\title{First document}
\author{Hubert Farnsworth \thanks{funded by the ShareLaTeX team}}
\date{February 2014}
```

If you write **`\usepackage{...}`** in the main body of the document (after **`\begin{document}`**) instead of in the preamble, you will generate the error message shown below.

main.tex, line 7

LaTeX Error: Can be used only in preamble.

See the LaTeX manual or LaTeX Companion for explanation. Type H for immediate help. ... l.4 \usepackage {amsmath} Your command was ignored. Type I to replace it with another command, or to continue without it. \[1

To fix this error, make sure that all **`\usepackage{...}`** commands, as well as **`\documentclass[...]{...}`**, are written before **`\begin{document}`**. To learn more about how to structure a document in LaTeX, check out our [documentation](/latex/latex-basics/01-learn-latex-in-30-minutes.md).


---

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