> 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/zh-tw/wen-yu-da/66-i-m-trying-to-include-urls-in-my-.tex-or-.bib-but-i-got-an-error-missing-inserted.md).

# 我嘗試在我的 .tex 或 .bib 中加入 URL，但出現錯誤「Missing $ inserted」

您的 URL 可能包含一些底線字元 `_`，這些在 LaTeX 中是特殊字元——在數學模式下它們是下標運算子，例如 `$x_i$` 會產生 $$x\_i$$。一般來說，如果你想在一般文字中使用字面上的底線字元，就必須將它跳脫為 `\_`.

幸好有一個更簡單的方法可以包含帶有底線的 URL。如果你加上 `\usepackage{url}` 或 `\usepackage{hyperref}` 就在你的 `\begin{document}`，之後你就可以寫：

```latex
\url{https://www.example.com/url_with_underscore}
```

在你的文件中。

如需進一步詳情，請參閱 Overleaf 說明文章 [插入了缺少的 $](/latex/zh-tw/latex-cuo-wu/25-missing-inserted.md).


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