Online LaTeX Editor and Compiler with Live Preview

\documentclass{article}
\begin{document}
Hello, world.
\end{document}

\documentclass[11pt,a4paper]{article}

\usepackage[margin=2.5cm]{geometry}  % page margins
\usepackage{amsmath,amssymb}         % maths
\usepackage{graphicx}                % \includegraphics, \scalebox
\usepackage{booktabs}                % proper table rules
\usepackage{enumitem}                % list spacing control
\usepackage{hyperref}                % clickable links and references

% In the preamble:
\title{Comparative Study of Sorting Algorithms}
\author{A. Perera \\ University of Colombo}
\date{\today}

% Just after the document begins:
\maketitle
\tableofcontents
\newpage

\section{Top level}
\subsection{Second level}
\subsubsection{Third level}
\paragraph{Run-in heading} Text starts on the same line.

\section*{Unnumbered}   % starred = no number, not in the contents

First paragraph.

Second paragraph — a blank line is what starts one.

Force a line break: \\
Force a page break: \newpage
Vertical gap: \vspace{1cm}
Horizontal gap: \hspace{2em}

\textbf{bold}  \textit{italic}  \emph{emphasis}
\texttt{monospace}  \textsc{Small Caps}  \underline{underlined}
\textbf{\textit{bold italic}}

{\tiny tiny} {\small small} {\normalsize normal}
{\large large} {\Large Large} {\LARGE LARGE} {\huge huge}

\% \$ \& \# \_ \{ \}
\textbackslash        % a literal backslash — NOT \\
\textasciitilde{} \textasciicircum{}

``double quoted'' and `single quoted'
hyphen - , en-dash -- (ranges: 10--15), em-dash --- (an aside)
Ellipsis: \ldots

\usepackage{fontspec}

% Fonts resolve by FILE NAME here, not by family name — the sandbox
% has no system font directory for \setmainfont{Times New Roman} to search.

% Latin Modern, shipped with the engine:
\setmainfont{lmroman10-regular.otf}[
  BoldFont       = lmroman10-bold.otf,
  ItalicFont     = lmroman10-italic.otf,
  BoldItalicFont = lmroman10-bolditalic.otf]

% Liberation Sans, which rides along with every compile in fonts/:
\setsansfont{LiberationSans}[
  Path        = fonts/,
  Extension   = .ttf,
  UprightFont = *-Regular, BoldFont = *-Bold, ItalicFont = *-Italic]

\begin{center}   Centred    \end{center}
\begin{flushleft} Left       \end{flushleft}
\begin{flushright}Right      \end{flushright}

\begin{quote}
A short indented quotation.
\end{quote}

\begin{itemize}
  \item First point
  \item Second point
\end{itemize}

\begin{enumerate}
  \item Step one
  \item Step two
\end{enumerate}

\begin{description}
  \item[TeX] Knuth's typesetting engine, 1978.
  \item[LaTeX] Lamport's macro layer on top of it, 1984.
\end{description}

\begin{enumerate}
  \item Outer
  \begin{itemize}
    \item Inner bullet
    \item Another
  \end{itemize}
  \item Back to outer
\end{enumerate}

\usepackage{enumitem}

\begin{itemize}[noitemsep, topsep=0pt, leftmargin=*]
  \item No extra space between items
\end{itemize}

\begin{enumerate}[label=(\alph*)]
  \item becomes (a)
  \item becomes (b)
\end{enumerate}

Inline maths sits in the sentence: $a^2 + b^2 = c^2$.

Unnumbered display:
\[ a^2 + b^2 = c^2 \]

Numbered display:
\begin{equation}
  a^2 + b^2 = c^2
\end{equation}

$x^2$  $x_i$  $x_{i+1}^{2n}$
$\frac{a}{b}$  $\tfrac{1}{2}$  $\dfrac{a}{b}$
$\sqrt{x}$  $\sqrt[3]{x}$
$\sum_{i=1}^{n} i = \frac{n(n+1)}{2}$
$\int_{0}^{\infty} e^{-x}\,\mathrm{d}x = 1$
$\lim_{n \to \infty} \frac{1}{n} = 0$

\begin{align}
  (a+b)^2 &= (a+b)(a+b) \\
          &= a^2 + 2ab + b^2
\end{align}

\begin{align*}   % starred = no equation numbers
  f(x) &= 3x + 1
\end{align*}

$\alpha \beta \gamma \delta \theta \lambda \mu \pi \sigma \phi \omega$
$\Gamma \Delta \Theta \Lambda \Sigma \Phi \Omega$
$\leq \geq \neq \approx \equiv \sim \propto \pm \times \div \cdot$
$\in \notin \subset \subseteq \cup \cap \emptyset \forall \exists$
$\to \Rightarrow \Leftrightarrow \mapsto \infty \partial \nabla$

\[
\begin{pmatrix} a & b \\ c & d \end{pmatrix}
\quad
\begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}
\]

\[
f(x) =
\begin{cases}
  x^2  & \text{if } x \geq 0 \\
  -x^2 & \text{otherwise}
\end{cases}
\]

$\mathbb{R}$ $\mathbb{N}$   % blackboard bold (amssymb)
$\mathcal{L}$              % calligraphic
$\mathbf{v}$ $\mathrm{d}x$ % upright bold / upright roman
$\sin x$ $\log n$ $\max_i$ % predefined operators, upright and spaced
$\operatorname{argmax}_x$  % your own operator (amsmath)

\begin{tabular}{l c r}
  Left & Centre & Right \\
  a    & b      & c     \\
\end{tabular}

\usepackage{booktabs}

\begin{tabular}{lrr}
  \toprule
  Item     & Qty & Price \\
  \midrule
  Notebook &   2 &   850 \\
  Pen      &  10 &    60 \\
  \bottomrule
\end{tabular}

\begin{table}[h]
  \centering
  \begin{tabular}{lr}
    \toprule
    Metric & Value \\
    \midrule
    Precision & 0.91 \\
    Recall    & 0.87 \\
    \bottomrule
  \end{tabular}
  \caption{Model performance on the held-out set.}
  \label{tab:perf}
\end{table}

Results are in Table~\ref{tab:perf}.

\usepackage{multirow}
\usepackage{tabularx}

\begin{tabular}{lcc}
  \multicolumn{3}{c}{Spans three columns} \\
  \multirow{2}{*}{Spans two rows} & a & b \\
                                  & c & d \\
\end{tabular}

\begin{tabularx}{\textwidth}{lX}
  Term & X stretches to fill the line width \\
\end{tabularx}

\usepackage{longtable}

\begin{longtable}{lr}
  \toprule
  Name & Score \\
  \midrule
  \endhead
  Row & 1 \\
  % … hundreds of rows …
  \bottomrule
\end{longtable}

\usepackage{tikz}
\usetikzlibrary{arrows.meta, positioning, shapes.geometric}

\begin{figure}[h]
  \centering
  \begin{tikzpicture}[node distance=2.5cm]
    \node[draw, rounded corners] (client) {Client};
    \node[draw, rounded corners, right=of client] (api) {API};
    \node[draw, cylinder, shape aspect=0.3, right=of api] (db) {DB};
    \draw[-Stealth] (client) -- (api);
    \draw[-Stealth] (api) -- (db);
  \end{tikzpicture}
  \caption{Request path.}
  \label{fig:arch}
\end{figure}

\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\begin{tikzpicture}
  \begin{axis}[xlabel=$x$, ylabel=$y$, grid=major, width=9cm, height=6cm]
    \addplot[thick, domain=-3:3, samples=100] {x^2};
    \addlegendentry{$y = x^2$}
  \end{axis}
\end{tikzpicture}

\usepackage{graphicx}

\begin{figure}[h]
  \centering
  \includegraphics[width=0.8\textwidth]{diagram.png}
  \caption{An image loaded from a file next to the .tex.}
\end{figure}

\usepackage{subcaption}

\begin{figure}[h]
  \centering
  \begin{subfigure}{0.45\textwidth}
    \centering\rule{3cm}{2cm}
    \caption{Left}
  \end{subfigure}
  \hfill
  \begin{subfigure}{0.45\textwidth}
    \centering\rule{3cm}{2cm}
    \caption{Right}
  \end{subfigure}
  \caption{Two panels, numbered (a) and (b).}
\end{figure}

\section{Method}\label{sec:method}
As described in Section~\ref{sec:method} on page~\pageref{sec:method}.

\begin{equation}\label{eq:loss}
  L = \tfrac{1}{n}\sum_i (y_i - \hat{y}_i)^2
\end{equation}
Equation~\eqref{eq:loss} is minimised.

% First pass writes the numbers to the .aux file,
% second pass reads them back. Tectonic reruns automatically,
% so ?? here means the label is missing or misspelt —
% not that you need another compile.
\label{fig:results}   % definition
\ref{fig:results}     % use — must match exactly, case sensitive

\usepackage{hyperref}

\href{https://induwara.lk}{clickable text}
\url{https://induwara.lk/tools}
\texttt{[email protected]}  % \href{mailto:[email protected]}{...} to make it clickable

\hypersetup{colorlinks=true, linkcolor=blue, urlcolor=blue}

Ordinary text.\footnote{The note appears at the bottom of the page.}

\footnotetext[3]{Manually numbered note.}

Knuth introduced literate programming~\cite{knuth1984}.

\begin{thebibliography}{9}
  \bibitem{knuth1984}
  D.~E. Knuth, ``Literate Programming'',
  \emph{The Computer Journal}, vol.~27, pp.~97--111, 1984.
\end{thebibliography}

\documentclass[11pt,a4paper]{article}
\begin{filecontents}{refs.bib}
@article{knuth1984,
  author  = {Donald E. Knuth},
  title   = {Literate Programming},
  journal = {The Computer Journal},
  year    = {1984},
  volume  = {27},
  pages   = {97--111}
}
\end{filecontents}
\begin{document}
Knuth says so~\cite{knuth1984}.
\bibliographystyle{plain}
\bibliography{refs}
\end{document}

\usepackage{natbib}
\bibliographystyle{plainnat}

\citet{knuth1984} argued …      % Knuth (1984) argued
… as argued \citep{knuth1984}.  % … (Knuth, 1984).

\begin{verbatim}
def add(a, b):
    return a + b
\end{verbatim}

Inline: \verb|no escaping needed inside|

\usepackage{listings}
\usepackage{xcolor}

\lstset{
  basicstyle=\ttfamily\small,
  keywordstyle=\color{blue!70!black},
  commentstyle=\color{gray},
  stringstyle=\color{green!45!black},
  numbers=left, numberstyle=\tiny, frame=single,
  breaklines=true, showstringspaces=false
}

\begin{lstlisting}[language=Python, caption={Adding two numbers}]
def add(a, b):
    """Return the sum."""
    return a + b
\end{lstlisting}

\usepackage[a4paper, margin=2.5cm]{geometry}

% or per-edge:
\usepackage[a4paper, top=3cm, bottom=2.5cm, left=3cm, right=2cm]{geometry}

% landscape:
\usepackage[a4paper, landscape, margin=2cm]{geometry}

\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhead[L]{Project Report}
\fancyhead[R]{\leftmark}
\fancyfoot[C]{\thepage}
\renewcommand{\headrulewidth}{0.4pt}

\usepackage{setspace}
\onehalfspacing        % or \doublespacing

\usepackage{parskip}   % blank line between paragraphs, no first-line indent
\setlength{\parindent}{0pt}   % the manual equivalent

% Whole document — add the option to the class:
%   \documentclass[twocolumn]{article}

% Or just part of it:
\usepackage{multicol}
\begin{multicols}{2}
  Text flows down the first column and up the second.
\end{multicols}