Missing \begin{document}: what this LaTeX error means

This message means: LaTeX found before \begin{document} something that produces visible text. Two common causes: text in the preamble or a badly encoded accent.

Cause #1: text in the preamble

Everything you want to write goes after \begin{document}. Text before it triggers the error:

\documentclass{article}
Hello!   % text in the preamble -> Missing \begin{document}
\begin{document}
...
\end{document}

Move the text after \begin{document}:

\documentclass{article}
\begin{document}
Hello!
\end{document}

Cause #2: a badly encoded accent

An accent (é, è, à…) in the preamble, combined with an old inputenc declaration, is read as text and triggers the same error. Fix: modern \usepackage[utf8]{inputenc} + \usepackage[T1]{fontenc} (see Old packages).

Try it yourself

This example compiles. Move the word "Hello" above \begin{document} and recompile to see "Missing \begin{document}".

The method

1. Check that nothing visible comes before \begin{document} (only \documentclass and \usepackage).
2. Move any text after \begin{document}.
3. An accent in the preamble? Modernize inputenc/fontenc to UTF-8.
4. Is a } missing in a \usepackage[…]{…}? That can also cause this error.

An AI can fix the error — directly in your code

AI assistants (Claude, Gemini, ChatGPT…) know LaTeX very well: show them the preamble and they find the text or accent breaking things before \begin{document}. The usual drawback is the back-and-forth — copy, paste, repeat.

sarmate.net removes this round-trip with its MCP server: you connect the AI directly to your online editor. It reads your files, compiles them, analyzes the error log and fixes the code in place, with no copy-paste. You stay in control: nothing is changed without your approval.