Standalone TikZ to PDF or PNG

A TikZ picture normally lives inside a paper, but you often need the diagram as its own file: to reuse it in a slide deck, to hand it to a co-author who works in Word, to upload it where a PNG is required, or simply to avoid recompiling an expensive drawing on every document build. The standalone document class exists for exactly this. It typesets one picture on a page cropped to the picture’s size:

\documentclass[tikz,border=2pt]{standalone}
\begin{document}
\begin{tikzpicture}
 \draw (0,0) -- (1,1);
\end{tikzpicture}
\end{document}

What the class options do

The tikz option loads the TikZ package for you and tells standalone to crop the output page tightly around the tikzpicture, so the resulting PDF is exactly as large as the drawing, with no page margins. The border=2pt option adds a two-point cushion on all sides, which prevents strokes that sit exactly on the bounding box from being shaved off by viewers or printers. Compile this file like any document and the output is a small, tightly cropped PDF containing only the diagram.

That PDF is the format to prefer, because it is vector: it scales to any size without blurring, and dropping it into another document with \includegraphics works as described in a PDF page as a graphic. When a raster copy is genuinely required, convert the compiled PDF rather than recreating the drawing. Command-line tools such as pdftoppm -png -r 300 figure.pdf figure produce a 300 dpi PNG, and pdf2svg or Inkscape produce SVG. Export at 300 dpi or more if the PNG will be printed.

Caching pictures with externalize

Inside a large document, TikZ pictures are redrawn on every compile, and a handful of complex plots can dominate the build time. The external library fixes this by compiling each picture to its own PDF once, then reusing the cached file until the picture’s code changes:

\usetikzlibrary{external}
\tikzexternalize[prefix=tikz-cache/]

The prefix option keeps the generated files in their own folder. Externalization runs the compiler in a mode that spawns sub-compilations, so it needs shell escape enabled and interacts poorly with some setups; if it fights you, moving each big picture into its own standalone file and including the compiled PDFs achieves the same caching manually, with less machinery. Compile times in general are covered in shorter wait for the PDF.

One common mistake deserves a warning: do not screenshot a rendered diagram to get a PNG. Screenshots capture screen resolution, which looks acceptable in a slide preview and fuzzy everywhere else. Convert from the PDF, where the resolution is yours to choose.