How do I change \footnote font size in beamer presentation?

Question

I tried all methods from this question: How to change font family in footnote? and none of them work for me...

Answer 1

The "official" method to change the \footnote font size is a call to \setbeamerfont applied to the footnote beamer font.

Example:

\setbeamerfont{footnote}{size=\tiny}

Default is:

\setbeamerfont{footnote}{size=\footnotesize}

A complete example:

\documentclass{beamer}

\begin{document}
\begin{frame}
  Text \footnote{First footnote}

  \setbeamerfont{footnote}{size=\tiny}
  Text \footnote{Second footnote}

  \setbeamerfont{footnote}{size=\footnotesize}
  Text \footnote{Third footnote}

\end{frame}
\end{document}

Answer 2

The command setting the desired size is \footnotesize. It can be used also outside footnotes, for text matching the size of footnotes. If that text should be treated different, it should not use \footnotesize, logically. So let's rely on consistent use.

The command \footnotesize does some more than changing the font size, it adjusts further śpace values such as in lists and around math formulas.

As default, beamer loads size11.clo, there \footnotesize is defined as:

\newcommand\footnotesize{%
   \@setfontsize\footnotesize\@ixpt{11}%
   \abovedisplayskip 8\p@ \@plus2\p@ \@minus4\p@
   \abovedisplayshortskip \z@ \@plus\p@
   \belowdisplayshortskip 4\p@ \@plus2\p@ \@minus2\p@
   \def\@listi{\leftmargin\leftmargini
               \topsep 4\p@ \@plus2\p@ \@minus2\p@
               \parsep 2\p@ \@plus\p@ \@minus\p@
               \itemsep \parsep}%
   \belowdisplayskip \abovedisplayskip
}

Just to let you know what's the orignal. You could redefine \footnotesize. You could even to that using the original, for keeping the spacing values:

\let\oldfootnotesize\footnotesize
\renewcommand*{\footnotesize}{\oldfootnotesize\tiny}

Instead of the simple example \tiny you could use an arbitrary size by \fontsize{...}{...}\selectfont.

Answer 3

If you only want to change the footnote text size for a single footnote, as one occasionally has to do when citing long URLs, the graphicx package loaded with

\usepackage{graphicx}

provides the \scalebox{<scale>}{<text>} command, where <scale> denotes the ratio of the new size to the original size. For example:

The StackExchange website provides an almost infinite amount of \LaTeX\ wisdom!%
\footnote{\scalebox{0.8}{%
  \url{http://tex.stackexchange.com/questions/21741/how-do-i-change-footnote-font-size-in-beamer-presentation}%
}} 

The footnote in this example would be set to 80% of the normal size.